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.
Informative – yes. But I am not convinced that we (meaning Dr. Klotzbac) can reliably predict TC activity.
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.
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.
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
I seem to recall that Joe Bastardi also predicts a strong hurricane season.
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. 🙂
“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.
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.
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.
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.
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.
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!
“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.
Thanks Dr. Klotzbach for posting — great read.
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.
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!
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?
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?
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.
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
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?
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)?
Excellent contribution and discussion (at least most of it). I am sure that any real scientist will relish the discussion.
Dry Saharan air starting to disappear for the time being….
http://www.ssd.noaa.gov/eumet/eatl/flash-wv.html
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.