Klotzbach on: Atlantic Hurricane Season Analysis

NHC Tropical Storm Potential August 10th, 2010

NHC Tropical Storm Potential August 10th, 2010

Guest post by: Dr. Philip Klotzbach,  Research Scientist, Department of Atmospheric Science, Colorado State University

As an author on the Colorado State University (CSU) seasonal hurricane forecast, I read with interest the blog regarding “Global Tropical Cyclone Activity still at 30 year low” posted yesterday. I have started to receive questions from the media asking where the hurricanes in the Atlantic are. We forecast a very active season, calling for a total of 18 named storms, 10 hurricanes and 5 major hurricanes (compared with the climatological average of 11 named storms, 6 hurricanes and 2 major hurricanes). Before I go into more detail describing why I think it is too early to think that this is a seasonal forecast bust, I wanted to briefly address the global storm component.

I completely agree that tropical cyclone (TC) activity is very quiet so far for this year’s Northern Hemisphere season. The Northeast Pacific had no named storms during the month of July, which is the first time that this has happened since 1966. The Joint Typhoon Warning Center did not name its fifth storm in the Northwest Pacific until August 8, which is also a record. The North Atlantic has also been very quiet since Hurricane Alex in late June. Alex was the strongest storm in terms of wind speed in the month of June in the North Atlantic since Alma (1966).

With a moderate La Niña event, it is typical to expect reduced activity in the Northwest Pacific and the Northeast Pacific. It has been well-documented that storm formations in the Northwest Pacific shift northwestward in La Niña years (Camargo et al. 2007). Consequently, these storms have less time to track over warm ocean water before making landfall and therefore have less time to reach their maximum potential intensity.

Northeast Pacific storm activity is also typically reduced in La Niña years, due to anomalous upper-level easterly winds that develop at upper levels associated with the strengthening and westward-shifting of the Walker Circulation (Figure 1). From a climatological point of view, upper-level winds in the Northeast Pacific blow out of the east (Figure 2), so stronger upper-level easterly winds increases vertical wind shear, which is detrimental for storm formation. Upper-level winds in the North Atlantic’s Main Development Region (MDR) (defined as 10-20°N, 20-70°W) blow out of the west in a climatological average (Figure 3), so anomalous upper-level easterlies reduces vertical wind shear (Wang and Lee 2009).

Figure 1: Correlation between the August-October Nino 3.4 index and 200 mb zonal winds. These correlations imply that a La Niña event increases vertical shear in the Northeast Pacific while reducing vertical shear in the North Atlantic.

Figure 2: Climatological upper-level winds in the Northeast Pacific during the months of August-October. Note that the climatological upper-level winds are easterly (so upper-level easterly anomalies associated with La Niña increases vertical wind shear).

Figure 3: Climatological upper-level winds in the MDR of the North Atlantic during the months of August-October. Note that the climatological upper-level winds throughout most of the MDR are westerly (so upper-level easterly anomalies associated with La Niña reduce vertical wind shear).

I want to begin addressing the North Atlantic component of the TC activity by examining historical hurricane seasons in La Niña years. I selected years that had an August-October averaged Nino 3.4 index less than -0.5°C since 1950. I calculated August-October averages from the Climate Prediction Center’s dataset available here:

http://www.cpc.ncep.noaa.gov/data/indices/sstoi.indices

I thought that an easy way to examine the typical progression of these seasons was to see when the 2nd hurricane formed. So far in 2010, the North Atlantic has had only one hurricane (Alex). Table 1 displays the La Niña years since 1950 along with the date of 2nd hurricane formation and the seasonal Accumulated Cyclone Energy (ACE) index for that year. ACE is defined as the sum of the square of a named storm’s maximum wind speed (in 104 knots2) divided by 10000. The 1950-2000 average of this index was 96, and for the 2010 season, we are predicting a value of 185.

Table 1: La Niña years since 1950 along with the date of 2nd hurricane formation and the seasonal ACE accumulated in each year.

Year ASO Nino 3.4 2nd Hurricane Formation Date Seasonal ACE
1995 -0.66 8/1 227
1970 -1.04 8/2 40
1956 -0.63 8/10 54
1955 -1.39 8/12 199
1971 -0.63 8/15 97
1973 -1.20 8/20 48
1950 -0.75 8/20 243
1999 -1.01 8/22 177
1998 -1.17 8/25 182
1954 -0.98 8/27 113
1975 -1.34 8/30 76
1974 -0.53 8/31 68
2007 -0.92 9/2 74
1964 -0.86 9/3 170
1961 -0.52 9/3 205
1988 -1.55 9/9 103

The average date of 2nd hurricane formation for all of these years is August 21, and you will note that five years with very high ACE values of 170 or greater did not have their 2nd hurricane formation until August 20th or later. The 2nd storm in 1961 did not form until September, and that September went on to have four major hurricanes, a record for the month. So, from a climatological perspective, it is not time to write off the TC season yet.

With regards to sea surface temperature (SST) anomalies, they are still running at record levels across the MDR, based on data from the NCEP/NCAR Reanalysis. I calculated the July SST over the MDR and have plotted the timeseries from 1948-2010 below (Figure 4). July 2010’s value was at record levels, approximately 0.1°C greater than it was in 2005. Calculations were made from the following website:

http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl


Figure 4: July SST averaged over the MDR. The value of 27.5°C reached in 2010 is the warmest on record, beating out 2005 and 1958 by approximately 0.1°C.

I tend to disagree with the SST analysis given by Steve Goddard yesterday. Other SST datasets that I look at in real-time tend to agree with the fact that the MDR is running at record or near-record levels right now. Here’s an additional analysis from NOAA (Figure 5):

Figure 5: Real-time SST anomaly analysis from NOAA.

In addition, analysis from the Advanced Very High Resolution Radiometer of the difference in SST between 2010 and 2005 indicates comparable SSTs throughout the MDR (Figure 6).

Figure 6: SST difference between 2010 and 2005. Note that there are only small differences between the two years.

The sea level pressure anomaly and low-level wind pattern in July would also tend to reinforce the very warm SST anomalies that were already in place from the spring. Figure 7 displays the SLP anomaly pattern in July, while Figure 8 displays the 925-mb wind anomalies. The trades were very weak in July, which is to be expected from the pressure gradient pattern observed in Figure 7. Very weak trades were observed over the MDR, which feeds back into continued warmth due to reductions in mixing and upwelling.

Figure 7: Anomalous sea level pressure in July. This pressure gradient pattern drives anomalous low-level westerly flow, thereby weakening the trades across most of the MDR.

Figure 8: Anomalous 925-mb winds in July. Note the anomalous westerly flow across most of the MDR, implying weaker trade winds (which feed back into warmer SSTs).

With that being said, it does appear that TC activity in the Atlantic should increase over the next couple of weeks. There are a couple of systems that currently have a high chance of formation into TCs in the next 48 hours according to the National Hurricane Center’s website. In addition, we should be heading into a more favorable large-scale regime for TC formation according to the latest Madden-Julian Oscillation forecasts. I showed in a paper published earlier this year that when the MJO is located in Phases 1 and 2 (convectively active over the Indian Ocean), it reduces vertical wind shear in the tropical Atlantic, thereby providing a more conducive environment for formation on a shorter time-scale basis (Klotzbach 2010). The GFS ensemble is hinting that the MJO may be amplifying in the Indian Ocean in the next couple of weeks (Figure 9).

Figure 9: Ensemble GFS forecast for the MJO over the next two weeks.

To summarize, I would say that it is too early to discount seasonal forecasts issued by CSU, NOAA and other agencies. Our August forecast has shown significant skill over the period from 1984-2009, with our average real-time forecast error over that time period being ± 2.2 named storms, ± 1.7 hurricanes and ± 1.1 major hurricanes. Correlations between our early August predictions and post-31 July TC activity are approximately 0.60 for most predictands over that same period. Full forecast verifications from CSU are available here:

http://tropical.atmos.colostate.edu/

NOAA’s forecasts show similar levels of skill. While seasonal forecasts do bust on occasion, these forecasts show moderate skill in real-time and should not be dismissed this early in the TC season.

References:

Camargo, S. J., A. W. Robertson, S. J. Gaffney, P. Smyth, and M. Ghil, 2007: Cluster analysis of typhoon tracks. Part II: Large-scale circulation and ENSO. J. Climate, 20, 3654-3676.

Klotzbach, P. J., 2010: On the Madden-Julian oscillation-Atlantic hurricane relationship. J. Climate, 23, 282-293.

Wang, C. and S.-K. Lee, 2009: Co-variability of tropical cyclones in the North Atlantic and the Eastern North Pacific. J. Geophys. Res., 36, L24702,doi:10.1029/2009GL041469.

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116 Responses to Klotzbach on: Atlantic Hurricane Season Analysis

  1. Philip,

    Thanks much for this. Your forecast is noted and bookmarked.

  2. Robert says:

    Very Interesting, thank you for contributing here.

  3. a jones says:

    June too soon.
    July stand by.
    August you must.
    September remember.
    October all over.

    Not much changed then since that little rhyme was coined by, I believe, our old friend Anonymous some time in the late 1600’s.

    Kindest Regards

  4. Kevin Kilty says:

    Last season was very quiet in the North Atlantic, and so there has perhaps been less stirring of near surface water with that cooler water below. I have often wondered if an unusually busy season, like 2005, leads to quiet season following, because of this cooling effect from stirring. I suppose what I’m asking is, is there an anticorrelation in TC count on a one-year lag basis? Anyone looked at this or know the answer?

    Last year I recall seeing a SST map after one of the named storms (I don’t recall the name–bob maybe?) passed through the western side of the North Atlantic. The cool track was obvious.

  5. tonyb says:

    Philip Klotzbach

    Thank you for your interesting article. Having studied SST’s for some time I am a bit bemused as to why such organisations as Hadley believe they have a historic data set of SST worth selling.

    SST’s were taken in a highly unreliable fashion from a tiny number of ships within very narrow well travelled sea routes. How can we relate modern SST to past SST when the original data is so scanty?

    tonyb

  6. John says:

    ‘Never mind the heat, climate change is hoax by gravy-train scientists’

  7. PJB says:

    Dear Dr. Phil (sorry, I couldn’t resist)

    I have followed hurricane activity on Mark Sudduth’s site since 2004. http://www.hurricanetrack.com You have been his guest and he references you regularly.

    Your contributions as well as your scholarship are well documented and highly valued. Thanks for spreading the wisdom. Facts beat rhetoric and agenda every time.

  8. Chris in Ga says:

    Very informative post! Much appreciated.

  9. Jack "In Oregon" Barnes says:

    I would like to see the maps above with -.5 to .5 being transparent. As in, normal. There is no base given in these maps, to show what is realistically normal. The use of warm looking colors for the baseline of normal, is intentional misdirection.

    Its the same type of built in looking hyper-boil as the writer of the following piece about the floating icebergs. The way it sounds, you would think that the whole Atlantic is in danger of this ice berg, yet if you click on the comparison of the sat views, it has not cleared the river its in, let alone shipping traffic.

    “An island of ice more than four times the size of Manhattan is drifting across the Arctic Ocean after breaking off from a glacier in Greenland. Potentially in the path of this unstoppable giant are oil platforms and shipping lanes — and any collision could do untold damage. In a worst case scenario, large chunks could reach the heavily trafficked waters where another Greenland iceberg sank the Titanic in 1912…”

    http://d.yimg.com/a/p/ap/20100810/capt.a441d83c1d1648d4b0da5176b057f75e-a441d83c1d1648d4b0da5176b057f75e-0.jpg?x=400&y=198&q=85&sig=CojcyKpLgqm._aIxgJ8dfg–

    http://news.yahoo.com/s/ap/20100810/ap_on_sc/eu_ice_island

    Wait until they blame the ice island for cooling the Atlantic hurricane season. You know at some point they will. If Greenland wasnt melting, we would have more Hurricanes… I give it 18 months…

  10. Ric Werme says:

    BTW, as I’ve noted in one of the NOAA updates at http://wattsupwiththat.com/2010/08/05/noaa-still-expects-active-atlantic-hurricane-season-la-nina-develops/#comment-448571 the Klotzbach/Gray forecast is unchanged between the June and August forecasts.

    Well, the predictions are the same, the data behind them is two months fresher.

    Very good reading, and very informative, even when the forecast busts.

  11. Stephan says:

    Well these SST’s are not showing any warming (click on Sea Surface)
    http://discover.itsc.uah.edu/amsutemps/
    My guess that if surface sea and land Satellite data in AMSU continues as is there is NO WAY 2010 will even come close to being the “warmest”. BTW 2010 has not finished so to say 2010 warmest on record ain’t gonna work…….
    Also no way will global ice be remotely close to an anomaly just check our warmista pal at CT (just joking)

  12. R.S.Brown says:

    You can always see which way the wind blows from Africa
    to South/Central America & the Carribean I here :

    http://www.ssec.wisc.edu/data/comp/cmoll/cmoll.html

    The “zoom” feature is handy to limit the viewing area.

  13. MinB says:

    Dr. Klotzbach,

    Thank you so much for the time you put into this post. Many of us are interested in these forecasts as increased TC activity is often linked to AGW. I didn’t see any direct reference to this in your post. Would you care to comment?

  14. P.F. says:

    This guest post by Dr. Klotzbach is a perfect example of what this blog site is all about and the high integrity it continues to demonstrate.

  15. Robert of Ottawa says:

    I must say that, contrary to my past life experience, I am finding Russian TV (RT) a bastion of objectivity and news coverage in comparison to the CBC, BBC, ABC, NBC, xBC TV networks.

  16. Eric Anderson says:

    Dr. Klotzbach, thank you for an interesting and informative post. It is great to read your perspective on some of the items that go into making the forecasts. Will be interesting to see how the season shakes out.

  17. savethesharks says:

    a jones says:
    August 10, 2010 at 3:35 pm
    June too soon.
    July stand by.
    August you must.
    September remember.
    October all over.

    Not much changed then since that little rhyme was coined by, I believe, our old friend Anonymous some time in the late 1600′s.

    ==========================================

    Some of the deadliest North Atlantic/Carribbean hurricanes have occurred in October, unfortunately, so that little rhyme really can not apply.

    Most recently, Mitch which hit late October 1998 in Honduras….10,000 dead.

    http://www.wunderground.com/hurricane/deadly.asp

    Also this list does not include the ones that have had a severe impact on the United States,

    such as CAT-4 Hazel in October 1954,

    Cat-4 Wilma (which ravaged Cancun for 2 days) and then took a hit on Florida in October 2005,

    also, the only Category 4 to have ever hit where I live, which did the following in October 1749:

    “Hurricane of October, 1749–The storm was perhaps one of the strongest storm ever in the Mid-Atlantic. According to Rick Schwartz, the hurricane produced a huge tidal surge of 15 feet. Based upon that observation, many experts believe that this system was a Category Four on the Saffir-Simpson Scale. It was responsible for creating Willoughby Spit, a small area of land near Norfolk that was inside the Chesapeake Bay.”

    http://www.hurricaneville.com/historic.html

    In October, its not over…at all.

    Chris
    Norfolk, VA, USA

  18. Doug Proctor says:

    Dr. Klotzbach of CSU writes: “Our August forecast has shown significant skill over the period from 1984-2009, with our average real-time forecast error over that time period being ± 2.2 named storms, ± 1.7 hurricanes and ± 1.1 major hurricanes. Correlations between our early August predictions and post-31 July TC activity are approximately 0.60 for most predictands over that same period.”

    I’m trying to get a success idea of this. “0.60” sounds like 6 out of 10 right, bit better than 5 out of 10. Am I mislead here? We adult workers know that departmental “successes” often are technical successes, not real successes, as funding, promotions and self-esteem are controlled by perceived competence. How much better than guessing from personal memory are they? Their predictions are based on Hansen data: if that data is tainted with inaccurate adjustments, they should predict more hurricanes that occur as time goes by, their sense of warmer conditions getting out of step with reality.

    And what of Dr. Simian?

  19. Jim Cripwell says:

    What I find curious is that we can have a storm like Colin that starts, but then does not develop. I would have thought that if condiditons were conducive for storm development, then Colin would not have behaved the way it did. But then, I know nothing about hurricanes.

  20. jorgekafkazar says:

    Robert of Ottawa says: “I must say that, contrary to my past life experience, I am finding Russian TV (RT) a bastion of objectivity and news coverage in comparison to the CBC, BBC, ABC, NBC, xBC TV networks.”

    You know, I’ve noticed the same thing, but was afraid to say so. They must be doing something right. Oh, the irony!

  21. jorgekafkazar says:

    Nice post. Very helpful. Thank you, Dr. Klotzbach!

  22. Frank K. says:

    Thank you, Dr. Klotzbach – very interesting indeed. Right now, there’s not a lot out there that looks like a threat to the Gulf or Eastern seaboard, but that can change very quickly.

    Now, looking at the calendar we have about 12 – 13 weeks left in the season, and your forecast is calling for 18 named storms, 10 hurricanes and 5 major hurricanes. We’ve had 3 named storms and 1 weak hurricane so far. So that leaves 15 more storms and 9 more hurricanes. We will need to average at least one storm per week, and nearly one hurricane per week and one major hurricane every 2.5 weeks. I suppose it is possible (never discount mother nature!), but…

  23. Liz says:

    I will admit that I have not read through all of the comments and some of the article was a mystery to me, but…. I do have some questions when “experts” talk of the history of storms.

    How does one mention that a year had “the most number of storms” or not, when there has been so much technological changes in recent years that improves the recording, or misrecording, of data.

    We now have satellites that tell us that there is a storm in the middle in the atlantic ocean. Airplanes go in to check on it. That storm rates as a TS, TD or a hurricane but never touches land. So, we know about it now and count it as a storm. But what about 100 years ago? What about 1000 years ago?

    There was something on this site a few weeks ago that talked about improved sun spot analysis, so there will now be more sun spots?

    Yes, I am not sure about what is happening – part of the reason is that our methods of observation has improved so much over recent years. So, claims of the hottest, wettest, coldest, most, least, etc needs to be described relative to the actual time of observation and there needs to be little asterisks attached to the data when methods improve.

  24. Chris R. says:

    To savethesharks

    That little Jamaican jingle is intended to reflect an average time distribution of hurricanes. And the “October, all over”, refers to the end of October. Once again, in the Caribbean, there is a festival called “Returning Thanks”, which is meant to give thanks for being spared during hurricane season. When I was in the U.S. Virgin Islands, that festival was held October 25th.

  25. Rhoda R says:

    They’ve already issued a Tropical Storm Warning. It’s in effect until thursday evening.

  26. GAZ says:

    Informative – yes. But I am not convinced that we (meaning Dr. Klotzbac) can reliably predict TC activity.

  27. Rich Apuzzo says:

    Sure, things might get active…but in all seriousness, it’s quiet with no serious hurricane threat in the next 7 to 10 days. 93L is doing nothing and won’t develop in the central Atlantic and TD 5 is less than impressive and will likely be a weak TS at most before landfall.

    If we really had a good handle on what creates busy seasons we wouldn’t be in such a multi-year lull. To my recollection, there have been above normal seasons forecasted since 2005, but we haven’t seen that in reality…and with the NHC naming numerous questionable storms in recent years (much like counting sunspots that couldn’t have been seen 50 years ago), including Bonnie and Colin this year, I think that the hype of the season was at least as flawed as the forecasts appear to be, to date. That can change, but as Ryan Maue pointed out, we would need to see a record storm pace over the next 2 months to reach forecast levels.

    Since numbers mean things, and since the public doesn’t understand ACE, I would have preferred to see how many named storms occurred in all of the years listed above. High ACE can come from a few big storms, but a quiet season.

    Additionally, with record or near-record warmth in the Atlantic, is it possible that water can be too warm for good tropical development in some parts of the world…maybe adding to mesoscale turbulence and shear that slightly cooler waters might not produce? Just a random thought…but when the “experts” list all the wonderful reasons for a nasty season and the best we can do through mid August is just two suspect tropical storms and one brief cat 2 hurricane, it naturally leads to some doubt.

    I have always favored CSU over the NHC for forecasts, but recent years have me wondering if there is something else we need to be looking for to aid / prevent a busy tropical season in the Atlantic.

  28. RACookPE1978 says:

    And just 90 years ago, at the turn of the century when coal-fired ships were still the exception and only a few oil-burning direct-drive piston-driven steam ships were just beginning to be bought for the world’s richest Navies as “their latest technology,” I think of the tens of thousands of sailors lost and (literally!) foresaken in the equatorial doldrums …. Lost with no wind for their sails, no fresh water, no safe drinking water but that stored below in barrel little changed from Magellen, no well-preserved food nor fresh food of any kind.

    What would they have given to see a satellite image of the ocean’s winds in real time? To get a simple Loran fix of their location, or a GPS plot of their ship’s location and a radio to contact the world if they were threatened with disaster or hurricane weather?

    But we are told that today’s technology is the ultimate and new energy sources for the year 2100, 2200, and 2300 must be based on 6 hours of solar power per day.
    Wind turbines = that blows in some regions only 60 days a year.
    Green fuels that take food from children and burns it in a liberal’s carbon-trading trust fund.

  29. Enginear says:

    Thank you Dr. Klotzbach for a very informative article. Living just outside of New Orleans I have a lot of interest in hurricanes. I do agree it is too soon to call the season a bust but I can hope can’t I? I really don’t believe we are vary good at predicting the tropical storms a season ahead but the continued effort should help us improve through time.

    Anyway, it’s nice to have a rebuttal from one ther actual people involved with the forecast. It just helps frame the debate objectively. Just so you know where I stand I am not a believer of CAGW but do believe continuing working on the science of climate.

    Thanks again,
    Barry C. Strayer

  30. stan stendera says:

    I seem to recall that Joe Bastardi also predicts a strong hurricane season.

  31. Amino Acids in Meteorites says:

    John says:
    August 10, 2010 at 3:50 pm

    ‘Never mind the heat, climate change is hoax by gravy-train scientists’

    Nice video. I thought Piers Corbyn handled himself very well. There’s so many that have criticisms for Piers Corbyn. Yet he is right so many times. I’ll listen to him and not the critics. :-)

  32. GW says:

    “To summarize, I would say that it is too early to discount seasonal forecasts issued by CSU, NOAA and other agencies. ”
    ______________________________________________________________________________________
    Of Course It is ! I have been reading Dr. Gray’s CSU forecasts since 1997, and one thing to be learned from them is that the season doesn’t REALLY start until mid-August, which is still a week away ! The very few seasons where anything formed in June or July are highly atypical, just not unprecedented (especially given modern satellite technology).

    I remember when Dr. Gray introduced you as his research associate quite a while back. Congratulations on having earned your degree, Dr. Klotzbach.

  33. John F. Hultquist says:

    Doug Proctor says:
    August 10, 2010 at 4:54 pm

    About that 0.6 correlation, or ‘r’. What was done to get this number doesn’t get explained in this post. However, generally to get an idea of how well your idea works is to square the ‘r’ and multiple by 100 and use this as a percent of statistical variance explained, so this would give you 36%. If this is so in this case they still have a lot of explaining to do!

    The above could be wrongl. It could be that there is something else being done here and, if so, someone will soon tell us.

  34. George E. Smith says:

    Dr Klotzbach,

    I just returned form a weeks fishing trip to the Loreto region of the Sea of Cortez. in Late July, the SSTs are typically somewhat above 86 deg F (30 deg C) and this seems to be a “tipping point” Temperature for the Dorado (Mahi-Mahi) to show up in good numbers; along with some marlin and lots of sailfish if it isn’t too hot.

    So this year it was somewhat of a bust; and I measured SSTs (with an actual real thermometer in the water) of only 82 F over perhaps 400 square miles of the Loreto Bay region during the week; while near surface (< 1metre) in the shade air Temperatures were typically 88 deg F over the very same 82 SSTs.

    No Dorado, Sails or Marlin except for an odd straggler.

    So does this sound like a result of the present La Nina situation in the Pacific; or do you have some other explanation for the unseasonally low SSTs for the Cortez.

    No I don't expect you to explain where the fish went; just does the Temperatures seem to make sense. Another person in the La Paz region was measuring pretty much the same Temperatures.

    So I figure if Dr Hansen can extend thermometer readings for 1200 km; between the two of us I guess we must have completely surveyed the whole Cortez.

    Your essay here looks very interesting; thanks for taking the time to present this.

  35. Mike Jonas says:

    There was a study some time ago which showed that high Atlantic storm activity was associated with global cooling phases, not warming. I downloaded (in 2008) the chart from the study, which I have put here
    http://members.westnet.com.au/jonas1/hurricanes.jpg
    but I can’t yet find a link to the full article.

    If the study was correct, we can expect Atlantic storm activity to increase.

  36. Jim Clarke says:

    So far this season, upper level wind shear has done a number on most of the potential tropical cyclones. Even the ones that do develop, like the brand new T.D. #5, have struggled with wind shear and have looked pretty ragged. This is very typical for early season storms. When the wind shear diminishes, and it will, Katie bar the door.

    “…And thick and fast
    They came at last
    And more and more and more.
    All hopping through the frothy waves
    And scrambling for the shore!”

    And that is the question: Will the majority of the storms recurve before making it to North America, or will they be driven westward to eventual landfalls, scrambling for our shores? I don’t know about the rest of you, but I got a bad feeling about this.

    Unlike AGW, hurricanes happen. Always have. Always will. And this year is still shaping up to be one to remember.

  37. TomRude says:

    Hardly convincing!

    As for Hurricane genesis and development, there is a lot more than meet the eyes in particular with the groundbreaking work of Makareva that is challenging the accepted concepts. Makarieva A.M., Gorshkov V.G. (2009) Condensation-induced kinematics and dynamics of cyclones, hurricanes and tornadoes. Physics Letters A, 373, 4201-4205.
    And
    Makarieva A.M., Gorshkov V.G., Li B.-L., Nobre A.D. (2010) A critique of some modern applications of the Carnot heat engine concept: the dissipative heat engine cannot exist. Proceedings of the Royal Society Series A Mathematical, Physical and Engineering Sciences, 466, 1893-1902. doi:10.1098/rspa.2009.0581.

    http://www.bioticregulation.ru/pubs/pubs2.php

    Finally I urged anyone here to read “Dynamic Analysis of Weather and Climate” Springer 2010, by Leroux before taking any “Walker circulation” to the bank!

  38. Myron Mesecke says:

    “savethesharks says:
    August 10, 2010 at 4:31 pm
    Some of the deadliest North Atlantic/Carribbean hurricanes have occurred in October, unfortunately, so that little rhyme really can not apply.
    In October, its not over…at all.”

    Depends on how you define “all over”. Storms all over the place. Storms so strong that you are doomed and your life is “all over”. Neat thing about poetry. Much of it is open to interpretation.

  39. John from CA says:

    Thanks Dr. Klotzbach for posting — great read.

  40. Pat Frank says:

    I note that Figure 4 has no uncertainty bars (as seems usual in the climate business). An SST difference of 0.1 C is certainly a statistical tie, and likely, so is (+/-)0.5 C.

  41. bob says:

    What’s with all those color coded charts? Don’t you know some people cannot see colors very well?

    There goes another profession I cannot handle because of my color-blind minority status. Oh, woe is me!

  42. Robert of Texas says:

    I am wondering if the oil leak in the Gulf could have any effect on the formation of severe storms around it. It seems possible (maybe not plausible) that evaporation could be affected by a thin layer of oil on the surface. If you reduce evaportion, you impact the heat engine that revs a tropical storm up. Anyone know if this is even possible?

  43. JDN says:

    Phillip:
    A number of posters on WUWT have shown that, for surface temps, there is a tendency to adjust temps upwards using various, sundry and opaque explanations, or no explanation at all. Now, the whole hurricane forecasting business has been way off these last few years. Anyone who relies on SST data has been too high in their predictions. Are you sure there isn’t something similar going on with the SST dataset? In other words, are you personally watching out for the integrity of your input data or are you taking that data on faith?

  44. Wally says:

    I looked at the correlations for the data Dr. Philip Klotzbach kindly listed for us. Looking at date of second hurricane versus the seasonal ACE and ASO Nino 3.4 and seasonal ACE showed no correlation, both with R^2 less than 0.02. The average ACE for the years listed was higher than average at 130 vs 96, but there is so much year to year scatter there is little significance to that. I think Dr. Klotzbach is correct that it is much too early to say if this is going to be an active year or not based on prior years records. I’ll leave model interpretation to others.

  45. savethesharks says:

    Myron Mesecke says

    Depends on how you define “all over”. Storms all over the place. Storms so strong that you are doomed and your life is “all over”. Neat thing about poetry. Much of it is open to interpretation.

    =========================

    Was using poetic license, just like you are doing.

    Point is, some of the deadliest hurricanes *at least in homo sapien history* [do you like those asterisks, Liz?]…have occurred in October.

    http://www.wunderground.com/hurricane/deadly.asp

    I’m just sayin’ LOL

    Chris
    Norfolk, VA, USA

  46. Tom in Texas says:

    George E. Smith says:
    August 10, 2010 at 6:14 pm
    “…and I measured SSTs (with an actual real thermometer in the water)…

    Did you adjust the data for time-of-day observations?

  47. Tom in Texas says:

    George E. Smith says:
    August 10, 2010 at 6:14 pm
    “…and I measured SSTs (with an actual real thermometer in the water)…”

    Did you ADD a couple of degrees to adjust for the UHI effect (your boat)?

  48. Don Mattox says:

    Excellent contribution and discussion (at least most of it). I am sure that any real scientist will relish the discussion.

  49. savethesharks says:

    Dry Saharan air starting to disappear for the time being….

    http://www.ssd.noaa.gov/eumet/eatl/flash-wv.html

  50. Tom in Florida says:

    SSTs off SW Florida are around 90F and are not going to get any warmer. TD 5 may become a weak TS but drier air to the north has been flowing in and there is a fairly good wind shear aloft. I don’t think anyone would claim to be able to predict those two storm limiting elements accurately very far out. Once again, it takes a lot more than just very warm SST to create these monsters. We still have to see how Richard Holle’s predictions play out.

  51. Gary Pearse says:

    Dr K very interesting and informative on forecasting methodology. Most on this site don’t take issue with the very brave activity of Trp Stm forecasting per se but rather in blaming frequency on gw. You graciously did not do that found a respectful and thankful readership.

  52. Gerry says:

    Dr K,

    With all due respect, these things sound reasonable, and they sound as if they should matter, but do they in fact allow you to predict what you claim? Why have you been unable to predict the historic low ACE? Why have so many recent storms failed to live up to these predictions? Even if you nail this year (which I doubt based on 38 years of living in the gulf coast), you will have to hit the nail repeatedly in good times and bad to have a valid claim that you hold this elusive key.

    I second the call for where are the predictions of low years. The constant call for historic high numbers is something of a joke here at sea level.

    Gerry

  53. Michael says:

    I TOLD YOU THERE WOULD BE ZERO HURRICANES JUST LIKE LAST YEAR. WHY DON’T THEY LISTEN TO ME?

  54. LightRain says:

    “Our August forecast has shown significant skill over the period from 1984-2009, with our average real-time forecast error over that time period being ± 2.2 named storms, ± 1.7 hurricanes and ± 1.1 major hurricanes.”

    So if I said 9 named storms, 3 hurricanes and 2 major hurricanes I’d be right with 7-11 named storms, 1-5 hurricanes and 1-3 major hurricanes. That’s quite a range doc, 150% for named storms, 500% for hurricanes and 300% for major hurricanes.

    I rest my case.

  55. Latimer Alder says:

    Is there any good evidence that all this statistical effort produces better predictions than looking at chicken’s entrails or asking the Oracle at Delphi?

  56. James Sexton says:

    Dr. Klotzbach,

    I’d like to personally thank you for posting your thoughts here. I may have a different train of thought than most posters here. Personally, I’ve always recognized that some years have more hurricanes than others. I live in Kansas, so the hurricanes rarely effect me, but when they do, it is in the forms of tornadoes. I give little thought to either. They come, they go. Sometimes with more frequency than others, still, they come, they go.

    My question and my observation is, are you aware of the focus of hurricanes in regards to the climate change question? And, are you aware of your influence on the question of hurricanes? I’m not implying you should or shouldn’t change the way you forecast. That would be silly. Still, by your forecasts, regardless of the accuracy(I believe you’re more correct than wrong), some have told me that(your prognostications) are “proof” positive of climate change due to CAGW. I’m just wondering if you are aware of your influence in the discussion and how you deal with it. Please note, I’m not asking for your emotional response. I don’t care if you chant to your ancestors or do like I do (drink heavily), I’m wondering if you regard your statements as having impact on the CAGW discussion.

    I thank you for any response.

    James Sexton

  57. polishG says:

    Re: TomRude

    Walker circulation does play a role. Makarieva et al. say that hurricanes develop when there is much vapor in the atmosphere.

    When trade winds are weak, the income of moisture to the region of hurricane formation is slow. Whether temperatures are high or low at the equator, without intense vapor import hurricanes will not form actively — they would have no food!

    So weak trades and reduced hurricane activity do seem to me to agree with what Makarieva et al. would predict (little vapor –> few hurricanes). On the contrary, I see little agreement between the conventional paradigm (high temp –> many hurricanes) and what actually happens.

    Really, some physical considerations rather than pure statistics would be welcome.

  58. Ric Werme says:

    Mike Jonas says:
    August 10, 2010 at 6:20 pm

    There was a study some time ago which showed that high Atlantic storm activity was associated with global cooling phases, not warming. I downloaded (in 2008) the chart from the study, which I have put here
    http://members.westnet.com.au/jonas1/hurricanes.jpg
    but I can’t yet find a link to the full article.
    If the study was correct, we can expect Atlantic storm activity to increase.

    I believe that graphic came from CSU and Bill Gray, and is in the latest Klotzbach/Gray forecast at http://hurricane.atmos.colostate.edu/Forecasts/2010/aug2010/aug2010.pdf . Yep. Page 39, except the image there is updated to the recent THC data – 1980-1994 and 1995-2009.

  59. Thank you Dr. Klotzbach, a very interesting read. Predicting chaotic events takes more guts than I have. It is like predicting the outcomes of team sports with well matched opponents, not easy to do. My hope is you are on the high side. My logical alter ego tells me you are probably in the ballpark. My scouting experience tells me prepare for the worst and hope like hell for the best.

  60. Peter Walsh says:

    Has Dr Hansimian passed any comment yet?

  61. John Costello says:

    The Russians spent almost seventy years having to lie to survive–the scientific community had to lie and denounce the people they esteemed or go to camps. Now they don’t have to. When the nuclear winter fraud was being advanced by American scientists to “save the world from Ronald Ray-gun,” they laughed at it. This decade they told Putin it was a hoax (he signed the Kyoto Protocol for financial reasons.) Their big worry is global cooling.

  62. UK John says:

    I always prefer the blindfold and pin approach to weather forecasting.

  63. Peter Taylor says:

    Thanks for this post – much appreciated – but to follow up a question on the impact of some statements on the very public debate – especially in the lead up to Cancun and also the activity in parliaments and senates around the world – the new ‘record’ temperatures are very marginally above 1950, there being two obvious peaks and a trough in-between – and I doubt that the second peak is statistically significant in its ‘record’ above the first peak. The media will run with the ‘record’ from the official spokesmen who ought to know, etc.

    The real question for science is – what causes the peaks? Is there a cycle? What are the mechanisms that drive the cycle. And the question for policy is – why don’t people at NCAR/UCAR/NOAA – and you can add Hadley here in the UK, talk about cycles?

    These peaks and troughs coincide with both the Arctic Oscillation and the Pacific Decadal Oscillation – what do the oceanographers have to say? And what does the palaeo-record show about frequency and any longer term patterns?

    And a question about the oil slick – if you can help – there is a lot of speculation on the wilder blogs about the ‘Loop Current’ in the Gulf shutting down and affecting the North Atlantic Gulf Stream. It seems unlikely, but do you have any information on this? Could the very low ACE levels have caused the Loop Current to fade (I assume it is driven by wind patterns), and would this feed back to the Atlantic current system – or rather, would they be subject to a common cause?

  64. John Peter says:

    Well, if the “18 named storms, 10 hurricanes and 5 major hurricanes” do occur this year it will no doubt be blamed on AGW in the same way as Louise Gray is now quoting other well known “Alamists” for blaming Russian heat and Pakistani downpours on AGW here:
    http://www.telegraph.co.uk/news/worldnews/asia/pakistan/7937269/Pakistan-floods-Climate-change-experts-say-global-warming-could-be-the-cause.html
    I thought there had been similar events in the past, but maybe I am wrong. No doubt Pamela Gray have some comments on the behaviour of the Jetstream. Is it unusual and caused by AGW or just weather?

  65. Dave Springer says:

    @Dr. Klotzbach

    How’s about you apply tropical storm theory to make a year-by-year 30-year prediction?

    Just kidding. There’s no such thing as tropical storm theory. There is statistical analysis of the past and predictions made based upon it. In other words it’s actuarial science and can only properly be called science if we conflate math and science. A less flattering but more commonly understood characterization for weather and climate predictions would be to call them educated guesses.

    So let’s look at the possible variability:

    1973 had an intense La Nina (-1.20), its second named hurricane on 20 August, and very weak ACE index of 48.

    1950 had a modest La Nina (-0.75), its second named hurricane on 20 August, and very strong ACE index of 243.

    Here’s my educated guess for 2010 ACE. The average of 1950 and 1973 is 148 but due to the recent multi-year lull I’m going to move it closer to 1973 by adding in the average of all years (48+96+243)/3 or a 2010 ACE of 129.

    I’ll give you even money that my guess is closer than yours.

  66. John W. says:

    Dr. Klotzbach,

    First, thanks for coming here and providing this information. Hopefully, you won’t receive the same treatment Dr. Curry has received.

    I do have a problem. When the predictions based on a hypothesis fail, it’s time to reexamine the basics. Is the data set correct? Has it been interpreted and analyzed properly? Have the phenomena been modeled or simulated accurately? Has a key process or factor been omitted?

    You know this. Why hasn’t it been done? Or, if it has, why haven’t we seen the result of the reexamination?

    As Frank K. points out above, “We will need to average at least one storm per week, and nearly one hurricane per week and one major hurricane every 2.5 weeks” in order to match your prediction.

    My field is system analysis and engineering, but some of my experience has been obtained in pure research programs. Based on that experience, I can tell you the first problem you need to address (i.e. reexamine the basics): Your SST data is flawed.

  67. Dave Springer says:

    Mike Jonas says:
    August 10, 2010 at 6:20 pm
    There was a study some time ago which showed that high Atlantic storm activity was associated with global cooling phases, not warming. I downloaded (in 2008) the chart from the study, which I have put here
    http://members.westnet.com.au/jonas1/hurricanes.jpg
    but I can’t yet find a link to the full article.

    If the study was correct, we can expect Atlantic storm activity to increase.

    Based on nothing more than the current 30-year record lull it’s a pretty safe bet to say the only direction it will go from here is up. I’ll step out on an even longer limb and predict that after it increases to the next 30-year record high we can expect it to go down.

  68. Steven Kopits says:

    Good post. Data and analysis, that’s all that’s required.

  69. Tom_R says:

    First, at the time of this comment it seems that TD-5 has petered out before becoming a tropical storm.

    Secondly, hurricane predictions are almost always high. The bureaucracy doesn’t want to have people come back and claim they weren’t prepared because NOAA said it would be a weak hurricane season. I’m skeptical of this comment:

    >> Our August forecast has shown significant skill over the period from 1984-2009, with our average real-time forecast error over that time period being ± 2.2 named storms, ± 1.7 hurricanes and ± 1.1 major hurricanes. <<

    I wonder just how many of the forcast errors were too low. I doubt there were many years where that was the case, and suspect a plot of the error vs. frequency would not be centered on zero.

  70. Pete says:

    I hope everyone here realizes that the hurricane season is from June 1st to November 30th. So even though the most active part of the season if from August to October, this doesn’t rule out the possibility of a named storm or two in November. So this 12 or 13 week deal with one storm per week doesn’t necessarily have to happen to accomplish the 18 named storm forecast.

  71. Thanks for all of the comments. I’ll try to answer some of the questions here:

    With regards to hurricanes and AGW, an extensive discussion is located in our latest forecast on pages 38-49 here: http://tropical.atmos.colostate.edu/Forecasts/2010/aug2010/aug2010.pdf

    I have also published a paper that looked at trends from 1986-2005 in Geophysical Research Letters:

    http://tropical.atmos.colostate.edu/Includes/Documents/Publications/klotzbach2006.pdf

    With regards to our skill, a correlation of 0.60 implies that we can explain about 35% of the variability. Obviously, there is significant room for improvement here, but honestly, I would suspect that due to the inherent uncertainty in the climate system, only 50-60% of the variance is predictable. When I build a statistical model in hindcast mode using 3 or 4 predictions (e.g., using the past to predict the future), I typically achieve this level of variance explained. Obviously, there will be slight degradation when applying the forecast model in real time, which is why I attempt to build the dataset over a certain period, say 1948-1989 and then test the equations over an additional period 1990-2009. Having solid physical links between a predictor and hurricanes is also very important. I’d suggest that the interested reader look at our forecasts. There is a lot more than just numbers… a forecast typically runs 50-60 pages and discusses in detail the various models that we utilize to come up with our forecast numbers.

    I’m aware that the reliability of the data degrades as we go back further in time. However, we have to deal with the data we’re given. Am I positive that the MDR temperatures are exactly 0.1C warmer than they were in 2005? No, but given the wide variety of analysis techniques that we currently have, we can say with certainty that it’s very warm out there.

    We have redesigned our statistical models over time as more datasets have come online. When Dr. Gray started issuing seasonal forecasts in 1984, we only had about 30 years of reliable data. We now have the NCEP/NCAR Reanalysis which is, in my experience, about the most reliable dataset that we have for fields such as SLP, SST and zonal and meridional wind. These fields typically have better reliability than some other fields in the reanalysis, since they are mostly driven by observations. This dataset runs from 1948-present and is being updated in near real-time. Some surface datasets go back to 1900-1947, which although having less reliability, allow for some additional model testing.

    I’ve also published a paper in GRL looking at the skill of our forecasts over the period from 1984-2008:

    http://tropical.atmos.colostate.edu/Includes/Documents/Publications/klotzgray2009.pdf

    Thanks again for all of the comments!

  72. Ric Werme says:

    John W. says:
    August 11, 2010 at 5:09 am

    Dr. Klotzbach,
    First, thanks for coming here and providing this information. Hopefully, you won’t receive the same treatment Dr. Curry has received.

    Don’t worry about Dr. Curry – she knew the fight pit she was heading into. Don’t worry about Dr. Klotzbach – Dr. Gray has been in that fight a lot longer and is the main target.

    You might worry about Colorado State – they’ve never been great defenders of The Tropical Meteorology Project and seem to have little interest in defending them or helping attract grant money.

    I was never close to the details, and haven’t remembered much, but after some NSF money was reduced, AIG – Lexington Insurance came up with some support. I’m especially fuzzy on these details, but I think some post docs left around then, seeding the NHC’s hurricane prediction effort. Chris Landsea is also a CSU alumnus and is rebuilding the historical hurricane record from contemporaneous accounts from ship logs and newspaper reports.

  73. Peter Walsh says:

    John Peter above at 3.03a.m. comments on the Louise Gray article in today’s Telegraph. Here in Dublin, Ireland, the same article is reproduced in the Irish Independent this morning 11 June 2010. I cannot ever imagine the Jet Stream taking orders from us mere mortals. We didn’t actually know it existed until the early 1940s. However, my comment here refers to the last few of lines of this article which read: Quote; Prof Andrew Watson, of the University of East Anglia, said the extreme events are “fairly consistent with the IPCC reports and what 99 per cent of the scientists believe to be happening”. end quote. Um, the last time I believed in anything emanating from the UEA was NEVER. After the recent Climategate saga which we all know about, would you believe anything that came from one of their spokespersons?

    I also find the part which says that “99% of scientists believe to be happening”

    Um, again. I remember 30 to 40 years ago the only people who managed to get 99% support in anything, including a country’s General election, were the likes of Dictators who might alledgelly have opposition. Some of them actually managed to get 101% of the vote on the odd occasion. 99% is so far fetched that I suggest that you recount your figures in order to find the other missing 1%. It’s there, believe me and you can and will find it. If you can’t find it, then ask Phil where he hid it.

    I don’t despair at these people’s attitudes, I just with they would “get real”.

    Maybe one day, one of these dendrochronologists will see the wood for the trees!

    Professor Watson, if by any chance you are reading this, please have a look at the International Climate Science Coalition site and see how many mainstream scientists, REAL Scientists, have signed up to the Manhattan Declaration.

  74. Peter Walsh says:

    OOPS, I can’t spell allegedly, by the looks of it!
    PW

  75. Peter Walsh says:

    OOPS again,

    I gave the date as 11 June. Red faced, iIadmit that this should be 11 August 2010.

  76. Ric Werme says:

    Tom_R says:
    August 11, 2010 at 6:12 am

    Secondly, hurricane predictions are almost always high. The bureaucracy doesn’t want to have people come back and claim they weren’t prepared because NOAA said it would be a weak hurricane season.

    You seem to be confused between the Klotzbach/Gray forecasts from CSU and the far less interesting forecasts from the NOAA’s NHC. I would never call Bill Gray part of the bureaucracy and was pleased to be able to finally meet him at this May’s ICCC in Chicago.

    I wonder just how many of the forcast errors were too low. I doubt there were many years where that was the case, and suspect a plot of the error vs. frequency would not be centered on zero.

    The forecasting methodology of the Klotzbach/Gray forecasts is never quite static, but you can read about some of their retrospective testing that Phil mentioned above. Also, page 54 of their latest forecast compares the last six years (four forecasts per year) with final observations. Four were overpredicted, two were underpredicted.

    I suspect a surplus of overpredictions may be due to events happening that are hard to predict. El Niño one year shut down the hurricane season early one year, Saharan dust suppress Cape Verde hurricanes another year. Other than an early collapse of El Niño, there aren’t too many surprising events that boost hurricane production.

    Please make the plot, but I find the postmortems in the end-of-season summaries a lot more interesting. Let’s just say Gray has learned a lot from decades of trying.

  77. TomRude says:

    PolishG, I agree with Makarieva et al.
    However the Walker circulation is a myth that observation doesn’t support.(read Leroux)

  78. George E. Smith says:

    “”” Tom in Texas says:
    August 10, 2010 at 7:43 pm
    George E. Smith says:
    August 10, 2010 at 6:14 pm
    “…and I measured SSTs (with an actual real thermometer in the water)…

    Did you adjust the data for time-of-day observations?

    Tom in Texas says:
    August 10, 2010 at 7:48 pm
    George E. Smith says:
    August 10, 2010 at 6:14 pm
    “…and I measured SSTs (with an actual real thermometer in the water)…”

    Did you ADD a couple of degrees to adjust for the UHI effect (your boat)? “””

    The ONLY thing I adjusted was my glasses; changing from my everyday (driving) glasses to my everyday (Computer) glasses; so I could read the thermometer more clearly. Yes I admit that it would have been bett5er if I used everyday (reading) glasses; but then I don’t actually have any reading glasses; so my computer glasses have to suffice.

    I did not make any adjustments for time of day; since the only measurements that I made, were actually made at the time of the day for which I read the thermometer.
    Since Mother Gaia adjusts the Temperature to be correct at the time of day for which she adjusts it; then it is appropriate to only measure it for the times that I read the thermometer; so no interpolations or extrapolations are necessary.

    And since I did not actually measure the Temperature of the boat, then I had no informatin with which to make any sort of UHI correction. In any case Mexican fishing Pangas are typically colored inside such that they remain actually cooler than the ambient air Temperature; and the only air Temperatures measured were for air over the sea; not air over the boat. The data was noted as read from the instrumentation without any fudge factors being applied.

    A good experimentalist (or process engineer) designs his experiments so that his instruments directly measure the variables of interest; rather than measure something else, and then “inferring” the desired data from some assumed proxy relationship.

    People who do process control by proxy tend to design things that go ‘boom’ when you least expect it.

  79. Geologists are scientists, and at least 90% of the ones I know think that climatologists are FOS.

  80. Pascvaks says:

    Ref – Robert of Ottawa says:
    August 10, 2010 at 4:25 pm
    “I must say that, contrary to my past life experience, I am finding Russian TV (RT) a bastion of objectivity and news coverage in comparison to the CBC, BBC, ABC, NBC, xBC TV networks”
    __________________________
    True! This is climate change, not weather.

    Ref – Ric Werme says:
    August 11, 2010 at 6:23 am
    John W. says:
    August 11, 2010 at 5:09 am
    “Dr. Klotzbach, First, thanks for coming here and providing this information. Hopefully, you won’t receive the same treatment Dr. Curry has received.
    “Don’t worry about Dr. Curry – she knew the fight pit she was heading into. Don’t worry about Dr. Klotzbach – Dr. Gray has been in that fight a lot longer and is the main target.
    “You might worry about Colorado State – they’ve never been great defenders of The Tropical Meteorology Project and seem to have little interest in defending them or helping attract grant money.”
    __________________________

    I have a feeling that the Chinese are already well underway and putting together their own world class Tropical Meteorology Project. Colorado State is fast making themself into just another regional Community College – how the mighty are falling! I guess thumb twittling and day dreaming really can be dangerous.

  81. Tom Scharf says:

    Thanks for the informative post on the science behind the predictions. I fully support your continued work.

    But….I live in Florida and we hear the hurricane forecasts every year with more interest than most. You can quote all the statistics you want, but the hurricane forecasting the last 5 years has been nothing more than a random number generator.

    The error margins used are (necessarily) very large and even these are being missed. We basically get a low, medium, high forecast every year and last year was a good example of a forecast of “very high” season which ended up being extremely low (your specific forecasts may be different). This type of miss inspires very little confidence in future forecasts.

    I understand the complexity of the problem and the lack of hard historical data in which to derive the true cause / effect relationship of the indicators being measured. Don’t mistake this as criticism, as I haven’t heard any hurricane forecasters making outrageous claims of their forecast’s societal value to this point. It is a very difficult problem.

    The main point I want to make is that these simulations require a lot of iterations of test/validate cycles to accurately determine and scale the correct inputs for better results. Because seasonal forecasts only get one set of results per year, the models will struggle to “home in” on a better answer until better input data is available. This may take decades to accumulate. Compare this to the relative luxury weather forecasters have (daily results) and also hurricane track prediction (ten per year).

    I have seen this cycle in action over the last twenty years in Florida as hurricane tracking has gotten progressively better every year, and the reliability of the “prediction cone” and spaghetti models is now very good 48 hours out, and this has real value down here.

    Don’t feel too disadvantaged though, climate modelers have to wait 30 years to validate their models, and they are making all kinds of unsubstantiated claims about the efficacy of their results.

  82. Alexander K says:

    Thanks Dr Klotzbach for spending the time writing this excellent post.

  83. polishG says:

    Dear Dr. Klotzbach

    You say: “Having solid physical links between a predictor and hurricanes is also very important. I’d suggest that the interested reader look at our forecasts. There is a lot more than just numbers… a forecast typically runs 50-60 pages and discusses in detail the various models that we utilize to come up with our forecast numbers.”

    I am an applied physicist interested in the hurricane business. I read the paper by Makarieva and Gorshkov in Physics Letters A and I understood very well what they propose as the driving principle: air pressure drop caused by vapor condensation. They nicely demonstrate (albeit in an approximation) that the total pressure fall is a factor of 2.5 times the partial pressure of water vapor, with this additional (geometric) factor caused by radial convergence.

    We have phase transition — we have a pressure fall — we have winds. Fullstop. (By the way, I see here a nice analogy to the heat pipes as described by Grover in 1964. These devices employ the same principle to rapidly divert heat due to the fact that the fluid-carrier is accelerated by pressure gradients formed by phase transitions.)

    I also tried to find a competitive explanation elsewhere. I read a paper in Physics Today where hurricanes were described as heat engines extracting heat from the ocean. I was taught at school that this is impossible. That the heat content of the oceans, although huge, is useless for ordered processes.

    For you as an authority in the field, is it possible to explain to an educated person in numerical terms what determines the pressure fall in the hurricane (this is what Makarieva et al. do very convincingly, in my opinion). Just this question: why does the pressure fall over an area spanning several hundred kilometers by up to 100 mb? Just a quantitative hint? I am a physicist and I cannot see how air pressure can fall due to a “heat input”.

    Many thanks in advance.

  84. Richard Bayles, CEM says:

    Regardless of seasonal forecast,and revisions to a forecast, our job in Emergency Management, cannot be predicated on forecast but on the results of an unprepared community. Thank you for your’s and Dr. Grays research.

  85. Tom Scharf

    We hear the 30 year climate figure all the time, but the fact is that seasonal forecasts constantly invalidate the climate models.

  86. John W. says:

    Peter Walsh says:
    August 11, 2010 at 6:33 am
    …99% is so far fetched that I suggest that you recount your figures in order to find the other missing 1%. It’s there, believe me and you can and will find it.

    I don’t know, Peter. 99% of sceintists and engineeers in the defense industry think AGW is junk science.

  87. atmoaggie says:

    As Dr. Gray, himself, has said many a time, the bell simply hasn’t rung yet…

  88. Ric Werme says:

    polishG says:
    August 11, 2010 at 11:22 am

    I also tried to find a competitive explanation elsewhere. I read a paper in Physics Today where hurricanes were described as heat engines extracting heat from the ocean. I was taught at school that this is impossible. That the heat content of the oceans, although huge, is useless for ordered processes.

    A heat engine needs a source of heat, and sink that is colder. For tropical storms, those are the sea surface and the air above, basically the tropopause. The wind transfer of collecting heat (and latent heat as water vapor) along the surface, conversion of heat energy to mechanical during convection, and subsidence of dry air to complete the cycle is said to be an efficient heat engine. At least by Kerry Emmanuel. He’s gradually learning about the confounding variables that limit the energy a storm can develop. Even surface friction doesn’t introduce inefficiency – any heat released by slowing the wind will evaporate more water.

    On the other hand, if you put Emmanuel and Bill Gray in the same room, you may have to announce a storm warning. I think Emmanuel has mellowed a bit, but he’s still mostly a theorist and Gray more an empiricist.

  89. Hurricanes are nature’s way of moving heat quickly from lower latitudes to higher latitudes. The North Atlantic is very warm this summer, so I don’t find the case for a lot of hurricanes to be completely convincing.

    If the whole planet had a uniform hot temperature (like Venus) there wouldn’t be a lot of convective storms.

  90. This from Two-Week Forecasts of Atlantic Hurricane Activity (for two-week periods between August and October) http://hurricane.atmos.colostate.edu/Includes/Documents/Two_Week_Forecasts.html

    COLORADO STATE UNIVERSITY FORECAST OF ATLANTIC HURRICANE ACTIVITY FROM AUGUST 4 – AUGUST 17, 2010
    We expect that the next two weeks will be characterized by heightened amounts (130 percent or more) of activity relative to climatology. These new two-week forecasts have replaced the monthly forecasts that we have been issuing in recent years.
    (as of 4 August 2010)
    By Philip J. Klotzbach and William M. Gray
    This forecast as well as past forecasts and verifications are available online at http://hurricane.atmos.colostate.edu/Forecasts

    See “Meteorology for South Florida and the Caribbean”, at http://www.oarval.org/meteorologFL.htm

  91. savethesharks says:

    stevengoddard says:
    August 11, 2010 at 4:59 pm
    Hurricanes are nature’s way of moving heat quickly from lower latitudes to higher latitudes. The North Atlantic is very warm this summer, so I don’t find the case for a lot of hurricanes to be completely convincing.

    ===========================================

    That should be one of the very reasons that it should be very convincing.

    That as well as the sinking cool air in the Pacific in the means due to La Nina has displaced the upward motion east and west, to both the Atlantic and Indian Oceans.

    And a uniformly “hot” Atlantic is not a good comparison to the uniformly hot Venus.

    For all your extreme smarts, Steve [and I have a lot of respect for those smarts], you may be grasping at straws on this one.

    Chris
    Norfolk, VA, USA

  92. polishG says:

    Ric Werme says:

    A heat engine needs a source of heat, and sink that is colder. For tropical storms, those are the sea surface and the air above, basically the tropopause. The wind transfer of collecting heat (and latent heat as water vapor) along the surface, conversion of heat energy to mechanical during convection, and subsidence of dry air to complete the cycle is said to be an efficient heat engine.

    Yes, I kind of perceived this idea. I feel really odd that such things could pass as explanations in serious literature (if I got them right — please, tell me if I am wrong). If my student was telling this to me, he would not pass the exam.

    A sink and a source of heat do not make a heat engine. There can be a temperature difference with just heat conductivity, no mechanical output. This is what we routinely observe over the ocean — the temperature difference is sitting there (the troposphere is cold at all times) but there are no hurricanes.

    Then suddenly there is the same temperature difference, and hurricanes! I ask — why? The message I gathered from the PT article is because heat input has increased due to high wind speeds — and high wind speeds are due to high heat input — but, my apologies, this is exactly what Baron Münchhausen did when getting out of a swamp by pulling his own hair…

    It is like saying to guys who exhaust themselves perfecting the technological heat engines — folks, just make the engine move a little, then you get a huge output, because speed enhances heat input and heat input enhances speed, you will be surprised how much output you will get… how much heat you will be able to extract from the sea…

    Tell me where I am wrong, would be much appreciated.

  93. savethesharks says:

    Year ASO Nino 2nd Hurricane Formation Date Seasonal ACE

    1954 -0.98 8/27 113

    This year was one of the most active of recorded history for the East Coast of the US.

    Carol, Edna, Hazel [all of those 1950's names LOL].

    2nd hurricane formation was not until the 27th.

  94. savethesharks says:

    polishG says:
    August 11, 2010 at 7:09 pm

    ==================================

    I love listening out loud to the mind of a physicist or engineer trying to problem solve.

    Fascinating and inspiring at the same time. [I mean that.]

    Chris

  95. InterestedObserver says:

    I found Dr. Klotzbach’s post quite stimulating. I’ve also found some of the comments by other posters interesting.

    I do know that most people who focus their attention on tropical cyclone development do not make an automatic correlation between increased global warming and increased number of tropical cyclones. In fact, there is a fair amount of analysis out there that suggests the contrary i.e. few numbers of storms, but greater number of strong storms.

    I also had to smile at the person who commented that Russian scientists are more concerned about global cooling, when this summer they are experiencing the worst heat wave in the last 90 years…. perhaps they should have been a bit more concerned about warming trends after all….

    However, my attention was drawn most strongly to those who feel it is practically impossible to have 8 hurricanes in 13 weeks, or to have 15 more named storms before the end of November. To illustrate the fallacy of that thinking, consider the 1950 hurricane season. It was one of those selected by Dr. Klotzbach as part of his presentation in the above article. In 1950, there were 13 named storms, 11 of which became hurricanes, 8 of them major hurricanes (cat 3 – 5 winds). Between August 20 and October 21, TEN of those 11 hurricanes had their lives. SEVEN of the 8 majors formed during this time. This happened within a period of eight weeks. We have had seasons where there were four hurricanes at the same time. In 2007, seven storms formed in September alone, three of them hurricanes. And that is not the record for number of named storms in a calender month.

    My point is that the history of the Atlantic basin, not even including the so-called “suspect” data of the pre-satellite age, suggests that it is entirely possible for there to be an additional 3 storms this month, an additional 7-10 between now and the end of “all over October”, and possibly as many as two additional storms in November (the Atlantic as seen storms as late as Dec 9 in La Nina years).

    While I am not saying that Dr. Kotzbach’s forecast WILL verify, there’s certainly more than enough evidence in the reliable historical record to show that it is well within the realm of possibility.

  96. savethesharks says:

    I also had to smile at the person who commented that Russian scientists are more concerned about global cooling, when this summer they are experiencing the worst heat wave in the last 90 years…. perhaps they should have been a bit more concerned about warming trends after all….

    =========================

    Good post overall. Although the above words I would disagree with.

    We are entering a period of more extremes in climate, so record heat (and cold) (and dry and wet) should not be surprising.

    Just because Moscow has endured probably its worst heat wave on record, does not mean that the Russian scientists are not right about global cooling.

    Time….and the data….will tell.

    Chris

  97. Only by asking the right questions, do you get the right answers,
    electromotive ions drive the intensify of the precipitation,
    condensation rates drive the pressure drop,
    the oceans provide the heat to power the wind driven by convection,
    lunar declinational tidal forces move the atmosphere, that steers the storms,
    and the outer planets vary the total storm intensity.

    It is the relationships of these interactions that determine the outcome,
    balmy day with light mist, or angry sea, and winds all pi$$ed.

  98. The mayor of Moscow was bragging last year about how they control the weather through Russian weather modification technology.

  99. Dave Springer says:

    polishG says:
    August 11, 2010 at 7:09 pm

    A sink and a source of heat do not make a heat engine.

    Correct. It makes a heat pump.

  100. Dave Springer says:

    polishG says:
    August 11, 2010 at 11:22 am

    I also tried to find a competitive explanation elsewhere. I read a paper in Physics Today where hurricanes were described as heat engines extracting heat from the ocean. I was taught at school that this is impossible. That the heat content of the oceans, although huge, is useless for ordered processes.

    I’d point out that every hydro-electric generator in the world is run by gravitational energy that can be traced back to water which evaporated at sea level and condensed at some higher altitude. It falls as rain to some collection point higher than sea level and the potential (gravitational) energy is then extracted by having it drive some kind of bladed contraption as it flows to a lower level. That is definitely a heat engine. Without any manmade contraptions extracting gravitational energy I’d point out that all erosion from flowing water is actually mechanical work accomplished by the water cycle and that too is a heat engine. One might also consider the substantial damage done by winds in hurricanes, thunderstorms, and tornadoes. That damage is essentially mechanical energy extracted from the flow of gases in the heat pump which also qualifies it as a heat engine. Or the storm surge in a hurricane which lifts boats higher is another example of work being accomplished.

  101. JKrob says:

    PolishG asked…
    “…Then suddenly there is the same temperature difference, and hurricanes! I ask — why? The message I gathered from the PT article is because heat input has increased due to high wind speeds — and high wind speeds are due to high heat input — but, my apologies, this is exactly what Baron Münchhausen did when getting out of a swamp by pulling his own hair…”

    If I may, the thing that separates a mass of showers/thunderstorms from an organized tropical cyclone is the Upper-Level High (ULH) at the top of the storm. The ULH is what is driving the cyclone and causing the pressure drop at the surface. It is fed by the latent heat released from the moisture drawn up from below.

    The airflow in the lower levels into an organized storm is a fairly long path, round in circles, compaired to the slightly curved path out & away from the storm at the top. The ULH is pushing the exhaust air out away from the storm faster than is being supplied from below. Since it cannot draw air from above the tropopause, it must draw (lift) air from below. This lowers the pressure at the surface since the entire column of air across a relatively broad area is being lifted.

    The ability of the ULH to do this is governed by the temperature contrast from the center to the outer edges. The warmer the center of the ULH is, the greater it’s ‘pumping’ action is and since this heat is brought up from the surface, the warmer the water is, the stronger the ULH can be which translates to a stronger tropical cyclone.

    The upper levels if the tropical cyclones have always been neglected from monitoring mainly due to the difficulty of reaching it but I believe *that* is where the ‘engine’ of the tropical cyclone resides and everyplace else below that we look, we are just seeing the effects of the storm (low pressure, high winds, eye wall, etc.) but not the cause and that is why I think this new NASA project to discover the cyclone genesis may miss the mark because they are looking in the wrong area. I notice the NASA ER-2 (U-2) is not involved with the project.

    I have more details to this genesis theory if you are interested.

    Jeff

  102. BullDurham says:

    To All (slightly OT):
    I cannot but comment on the discussions here. Contrary to EVERY other Weblog on this topic (and most other topics, in fact), it is worth noting there are ZERO instances of the following terms: stupid, ignorant, idiot, moron, [profane and vulgar expletives deleted], and a whole host of others.
    Now that I’m in my seventh decade, it is refreshing to see such an anachronistic multilogue ongoing. (I’m NOT a climatologist, but have earned degrees in engineering, physics and management, so I consider myself an intelligent but untutored observer)
    THNX! to all participants.

  103. itronix says:

    It seems that some people are distracted by normal temperatures, anomalies near-.5 to .5, and thinking this means low hurricane count. If temps are normal, then you would expect a “normal” number of storms. (9 trop storms, 5 hurricanes). It would be other factors that influence above or below the norm.

  104. Paul Pierett says:

    Dear Dr. Klotzbach,

    Having correlated sunspot activity to Accumulated Cyclone Energy, temperatures, number of hurricanes, precipitation and lack of significant glacier growth since the mid-1980s, the biggest nemesis to your prediction this year is the lack of sunspot activity.

    You may wish to enter upper atmosphere humidity to your calculations. That measurement and critical ozone production have dropped in the last few years.

    The earth is cooling. We are now in a solar sunspot minimum.

    My work is at nationalforestlawblog.com
    Oct. Newsletter under my name.

    Most Sincerely,

    Paul Pierett

  105. Steve Keohane says:

    Ric Werme says: August 11, 2010 at 3:34 pm I agree with your assertion that hurricanes are removing heat from the ocean. I don’t have a picture on hand, but watching SSTs with the passage of a hurricane, shows a trail of cooler water in its wake.

  106. Ric Werme says:

    Steve Keohane says:
    August 13, 2010 at 7:22 am

    I don’t have a picture on hand, but watching SSTs with the passage of a hurricane, shows a trail of cooler water in its wake.

    See http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281997%29125%3C2716%3ASIOSST%3E2.0.CO%3B2 for a photo of Hurricane Edouward’s track which decreased SST by as much as 5° C. The effect is from both evaporation and mixing. Hurricanes that stall generally weaken after a day or two thanks to the losing warm water fuel.

    The same image is on page 76 of Kerry Emanuel’s Divine Wind, see my next comment.

  107. Ric Werme says:

    polishG says:
    August 11, 2010 at 7:09 pm

    Ric Werme says:

    A heat engine needs a source of heat, and sink that is colder. For tropical storms, those are the sea surface and the air above, basically the tropopause. The wind transfer of collecting heat (and latent heat as water vapor) along the surface, conversion of heat energy to mechanical during convection, and subsidence of dry air to complete the cycle is said to be an efficient heat engine.

    Yes, I kind of perceived this idea. I feel really odd that such things could pass as explanations in serious literature (if I got them right — please, tell me if I am wrong). If my student was telling this to me, he would not pass the exam.
    A sink and a source of heat do not make a heat engine.

    Fair enough – I hope you didn’t expect me to write the book. It has been done already, See Kerry Emanuel’s Divine Wind at amazon.com. (More in a bit)

    Given warm water on the surface and cold overhead, the next step is convection. Warm moist air is lighter than warm dry air and lighter still than cold dry air. Surface convects upward, condensing water vapor keeps the temperature warm as it jumps from the dry adiabatic lapse rate to the wet adiabatic lapse rate. If convection is strong enough, you’ll get a thunderstorm. Apparently you also need more than the typical mid-level humidity to get more than a thunderstorm.

    This still isn’t enough for a tropical storm, it needs a source of rotation around a core, this comes from things like Saharan waves off Africa, old extratropical storms, etc. Now the updrafts and rotation provide more air inflow, more wind, more evaporation. With an upper level ridge or anticyclonic system above, that provides ventilation to get the upwelling air out of the developing storm.

    The eyewall appears to be a point where radial force pulling in air can’t pull any further because it all goes into bending the wind. That forces air up, enhancing the convective forces. It also allows dry air above the storm to sink into the eye, hence the clearing and warm core nature of tropical storms.

    Emanuel’s book goes into all this in much greater detail and even has equations that let you estimate the top winds a hurricane can reach. (Including some stuff about “hypercanes” that pass a tipping point and enter the realm of the movie “The Day after Tomorrow” but let’s not go there!)

    If this link works – http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&field-keywords=diven+winds+emanuel&x=0&y=0&ih=36_3_0_1_0_0_1_0_1_1.152_769&fsc=-1 click on the “Look inside” link and search for terms like genesis, carnot, and Edouard for information starting at pages 93, 54, and 76.

  108. polishG says:

    Steve Keohane says:
    I agree with your assertion that hurricanes are removing heat from the ocean. I don’t have a picture on hand, but watching SSTs with the passage of a hurricane, shows a trail of cooler water in its wake.

    My observation is that any rain produces some cooling at the surface. Aren’t raindrops falling from a certain height in the atmosphere much colder than the surface? Hurricanes carry heavy showers, it does not surprise me they leave cold sea surface behind.

    If you have a heater in the room, try to remove heat from it by mixing the air. All you will get is a more uniform (higher) temperature of the room, no mechanical output.

  109. polishG says:

    JKrob says:

    If I may, the thing that separates a mass of showers/thunderstorms from an organized tropical cyclone is the Upper-Level High (ULH) at the top of the storm. The ULH is what is driving the cyclone and causing the pressure drop at the surface.

    This makes good sense to me as a general idea. My point is we need a pressure drop somewhere to drive wind. If we have a pressure gradient, we are there. My next question would be — what makes the high pressure at the top of the storm?

    I like the work of Makarieva and Gorshkov (2009) because they answer this question for the surface. If you know what a heat pipe is, the idea is amazingly clear. The pipe is filled with saturated vapor. Due to the temperature difference between the pipe ends (the cold and the hot) there is a pressure difference that can theoretically lead to vapor velocities comparable to the speed of molecules. This high vapor velocity makes heat pipes very efficient in conducting (latent) heat.

    Now let’s look at the hurricane as a (crooked, hockey-stick like) heat pipe. It has a long nearly horizontal part and a shorter nearly vertical end. The warm, vapor-rich air streams upward along the pipe to the center where it condenses at some height. The temperature difference between the pipe ends should be in the order of several dozen degrees. Most vapor condenses. If at start we have about 4% standard pressure of vapor, at finish we have nearly nothing. This accounts for the pressure drop along our crooked pipe and yields air velocities up to square root of 0.04 times the speed of molecules = 60 m/sec. To me, the hurricane is there.

    I like these numbers. It is ok to propose a qualitative idea, but to prove that it really means something one would need to bother about some rough zero-order estimates. If the physics is clear, to demonstrate such estimates to educated guys from the street would make no difficulty.

  110. polishG says:

    JKrob says:

    If I may, the thing that separates a mass of showers/thunderstorms from an organized tropical cyclone is the Upper-Level High (ULH) at the top of the storm. The ULH is what is driving the cyclone and causing the pressure drop at the surface.

    This makes good sense to me as a general idea. My point is we need a pressure drop somewhere to drive wind. If we have a pressure gradient, we are there. My next question would be — what makes the high pressure at the top of the storm?

    I like the work of Makarieva and Gorshkov (2009) because they answer this question for the surface. If you know what a heat pipe is, the idea is amazingly clear. The pipe is filled with saturated vapor. Due to the temperature difference between the pipe ends (the cold and the hot) there is a pressure difference that can theoretically lead to vapor velocities comparable to the speed of molecules. This high vapor velocity makes heat pipes very efficient in conducting (latent) heat.

    Now let’s look at the hurricane as a (crooked, hockey-stick like) heat pipe. It has a long nearly horizontal part and a shorter nearly vertical end. The warm, vapor-rich air streams upward along the pipe to the center where it condenses at some height. The temperature difference between the pipe ends should be in the order of several dozen degrees. Most vapor condenses. If at start we have about 4% standard pressure of vapor, at finish we have nearly nothing. This accounts for the pressure drop along our crooked pipe and yields air velocities up to (0.04)^1/2 times the speed of molecules = 60 m/sec. To me, the hurricane is there.

    I like these numbers. It is ok to propose a qualitative idea, but to prove that it really means something one would need to bother about some rough zero-order estimates. If the physics is clear, to demonstrate such estimates to educated guys from the street would make no difficulty.

  111. polishG says:

    Ric Werme says
    Fair enough – I hope you didn’t expect me to write the book. It has been done already, See Kerry Emanuel’s Divine Wind at amazon.com. (More in a bit)

    Thanks for taking the effort to explain things. It appears the paper I read in Physics Today was of K. Emanuel so I now realize my concerns are not about a marginal view.

    Surface convects upward, condensing water vapor keeps the temperature warm as it jumps from the dry adiabatic lapse rate to the wet adiabatic lapse rate.

    I am trying to get the point. Wet adiabatic lapse rate is smaller than the dry one, right? An air parcel will continue moving upward as long as it is warmer than the surrounding air. But if the adiabatic lapse rate is already wet (minimal?), what will enhance the upward movement of the air at the surface?

    If convection is strong enough, you’ll get a thunderstorm.

    To me, this is circular. It is here that I see the problem: what makes convection strong? Over a calm sea surface there is suddenly strong convection. I ask: why? Logically, I am ready to accept the answer of JKRob: because there is a strong pressure gradient in the upper atmosphere. If the cause of this gradient is identified and quantified, I am happy. I am also ready to accept the answer of Makarieva and Gorshkov, because they show a positive feedback between condensation, pressure drop formation and velocity. But with the heat engine concept my logic fails to be satisfied.

  112. Ric Werme says:

    polishG says:
    August 15, 2010 at 4:24 am

    > Surface convects upward, condensing water vapor keeps the temperature warm as it jumps from the dry adiabatic lapse rate to the wet adiabatic lapse rate.

    I am trying to get the point. Wet adiabatic lapse rate is smaller than the dry one, right? An air parcel will continue moving upward as long as it is warmer than the surrounding air. But if the adiabatic lapse rate is already wet (minimal?), what will enhance the upward movement of the air at the surface?

    I’m not certain we see the same things here. Convection starts at the surface due to warm water heating the air and adding water vapor (note water’s molecular weight is 1*2+12 = 14, N2 is 2*14=28, so water vapor is a lot lighter than air). That heat input is what initiates convection. As long as the air column is marginally stable, adiabatic cooling won’t be enough to stop convection.

    Heat initiates convection, unstable air allows it to continue.

    Check out Jeff Haby’s http://theweatherprediction.com/ which I probably should have though of first. He has notes on tropical storm development (I meant to include a plug for the Coriolis effect). A lot of stuff about convection centers on the “skew-T” chart which can keep you busy for a long, long time. Note especially comments about “CAPE” – Convective Available Potential Energy.

    If convection is strong enough, you’ll get a thunderstorm.

    To me, this is circular. It is here that I see the problem: what makes convection strong? Over a calm sea surface there is suddenly strong convection. …

    It’s a positive feedback loop – of course it’s circular. :-) Daytime sun heats the surface, and that heats the air. A typical tropical day has afternoon thunderstorms, so it’s more an issue of gathering a tropical wave into a depression and spinning that up in to a storm, and there’s nothing sudden about that. So far this year that seems to be a challenge even for nature.

    Watch some of the tropical waves as they develop, the NHC discussion is fairly decent, see http://www.nhc.noaa.gov/ and click on “Tropical Weather Discussion.” They spend a lot of time talking about convection and cyclonic winds. The surface analysis map, e.g. http://www.nhc.noaa.gov/tafb/ATSA_06Z.gif , is cluttered, but helps make the discussion comprehensible.

    I see the current discussion notes (downcased because I hate shouting):

    Tropical wave extends from 19N53W to 13N51W to 8N46W moving W 20 kt. Wave exhibits weak low level cyclonic curvature along the wave axis as observed on satellite imagery and satellite derived winds. A large area of dry air and Saharan dust is E of the wave axis to west Africa. Scattered moderate convection is 15N-16N between 50W-52W.

    Saharan dust is important – it blocks sunlight at mid-level altiudes and that both heats the air (reducing convective potential) and reduces sea surface heating (reducing energy input to surface air and reducing convective potential).

  113. polishG says:

    Ric Werme says
    It’s a positive feedback loop – of course it’s circular. :-) Daytime sun heats the surface, and that heats the air.

    First of all, thanks for further comments and links. I wish I could give more time to this than I have.

    But at the point above I have to disagree. And this is precisely where I see the problem. There is no positive feedback, the feedback is negative. Of course if the temperature drops sharply with height then some vertical movement (not necessarily ascending, by the way) can be initiated due to the convective instability of the fluid in the presence of gravity.

    The upward movement of the air volume we keep an eye on continues as long as the volume is warmer than the surroundings. But this very movement changes the initial sharp temperature profile and makes it close to wet adiabatic. What I mean, the movement that starts due to the fact that there is a sharp temperature gradient makes this gradient shallower. The movement does not sustain the instability that has caused the movement. It wipes it out instead.

    To me this is an obvious point. Enhanced mixing destroys the temperature difference on which a heat engine operates.

    In the hurricane like heat pipe model of Makarieva and Gorshkov the positive feedback loop is clear to me. Cooling rate and condensation rate are both proportional to vertical velocity. Vertical motion leads to condensation, condensation creates a pressure drop to elevate velocity and, in turn, raises the condensation rate.

  114. Jaco van Zyl says:

    Very good and interesting article, but …

    I quickly learned to just ignore these forecasts in general. Anyone can take a long shot the year before, then keep readjusting towards the end of the season, as the numbers are already on the table! Instead of listing the “Final Forecast” from previous years as reference, play open cards and start listing “First Forecast” from previous years for comparison. Maybe then I’ll start taking the good ones more seriously. From my analysis of these earlier numbers, most of these predictions are akin to playing Russian Roulette, and no better than “Aunt Sally’s best guess”.

    Also, the forecasts may be interesting and meaningful to meteorologists, or others interested in pure academics. For 99% of the population, there is a geographical interest that is more important than any of these numbers. As example, the year 2005 went down as the busiest season in recent memory in terms of numbers (as well as intensity). Yet, for the Carolinas it was about as quiet as 2009 (which meteorologically was an average year!)! In contrast, 1989 had only 11 storms … of which one was Hugo … and Charleston still shivers at the thought. It only takes ONE storm, and for the average citizen the importance of numbers is insignificant compared to location. If the forecast can one day nail the probability to be affected in a specific location, in a particular year … now THAT has value! But we already have that probability as an average over the years, right? Problem is, it is a constant … and I do not see us able to ever simplify complex environmental systems over time enough to make a sensible forecast possible. Until then, we will have to continue preparing for storms as if it is going to hit us next week … and be thankful that the track forecasts on individual storms improved dramatically in recent years :-)

  115. Paul Pierett says:

    Jaco,

    There are a lot of theories on the table and a lot of factors being played out as to the causes of a hurricane, which is a global warming event.

    Hurricanes can only happen for a short time each year over a period of a few thousand years during between ice ages before we slide into the next ice age.

    We have advanced only a little bit in the last 150 years in our understanding of this event. Unfortunately, global warming alarmists have muddied the water with miss-information.

    Fortunately, we have people like Dr. Klotzbach who have dedicated life long study to these events and their efforts should be recognized.

    As for predictions, I guessed this past spring, 7 named storms with a 50/50 mix of tropical storms and hurricanes and several tropical depressions.

    Why is that? Historically, during limited sunspot activity, the named storm numbers drop to reflect a slow global cooling that is constantly debated in the blogs.

    It is not a theory. It was observed in the 1878, Jan. Issue of Popular Science that fewer sunspots means fewer hurricanes. This could be a turning point in the science world if the hurricane numbers actually drop and show continued correlation to sunspot activity.

    Our science world needs to strongly minimize global warming due to sunspot activity so as to keep the masses stupid and those who thought up “Cap and Tax” and have invested in the carbon trading, happy.

    You will find sunspot activity ignored and or rejected by some of the popular science magazines and contributing scientists. It was downplayed by the IPCC in one of their recent reports

    And… They run the show.

    Most Sincerely,

    Paul Pierett

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