Hurricane Julia explodes — Atlantic has two coincident Category 4 hurricanes, very rare

UPDATE 5 AM AST: Second time in 100-years two coincident Category 4’s in the Atlantic…together, Igor and Julia have the highest coincident intensities on record.

Two major hurricanes exist simultaneously in the North Atlantic, a rare occurrence.  With the current intensities (110 knots +) of Julia and Igor, this has only happened 3-times in the past 60-years:  1950 [Dog & Easy], 1958 [Helene & Ilsa], and 1999 [Floyd & Gert].  But Igor and Julia are both very powerful major hurricanes, they are Category 4’s.

  • Unprecedented:  in our North Atlantic historical records, the forecast intensities of Igor and Julia during the next 12-24 hours will be unprecedented for coincident storms.  The only other time (we know of) coincident Category 4+ hurricanes occurred was in 1926 with Hurricane #4 and the Great Miami Hurricane (September 26 at 06:00 UTC).
  • More:  At 115 knots +, Hurricane Julia is the most intense storm that far in the Eastern Atlantic [-31.8W] joining other major hurricane east of -35W including Frances 1980 and Fred 2009.
  • Early morning September 15: 12-hour forecasts indicate a maximum intensity of 120 knots for Julia and 130 knots for Igor. Two coincident Category 4 hurricanes have not occurred since 1950.  The only occurrence since 1900 happened on September 15, 1926 at 06Z with Hurricane 4 [115 knots] and the Great Miami Hurricane [120 knots].
  • Thus, Igor and Julia will attain have attained coincident intensities that are unprecedented:  Igor:  130 knots & Julia: 115 knots.

Hurricane Julia has rapidly intensified during the morning hours of September 15, blowing up to Category 3 + (110 knots).  Meanwhile, closer to the USA mainland, Igor was packing 135 knot winds, just the smallest of margins weaker than Category 5.  Need 136 knots, but the NHC issues advisories in increments of 5 knots.  If Igor does not break the Category 5 plateau, it is possible a post-season re-analysis will bump the storm into the most extreme Saffir-Simpson category.

ACE has really picked up:  90 as of 00Z September 15… [note the Western Pacific is 83% below normal].

Coincident major hurricanes (96 knots +) in the Atlantic basin have not occurred very often since 1950.  To ferret out the occurrences, we need to go into the best-track database.

From the HURDAT best-track database, which I have put into a easily digestible form here:  Atlantic storm listing, it is trivial with a quick UNIX/Linux command prompt:

cat hurdat_1850_2009 | awk ‘($1 >= 1950 && $8 >= 100) {print $4}’ | sort -n -k 1,1 | uniq -d

1950090406 – 1950090518
1951090712 – 1951090800
1955091806 – 1955091900
1958092618 – 1958092800
1961091112 – 1961091200
1964090918 – 1964091000
1969081806 – 1999091500
1999091506 – 1999091512

But Julia is at 110 knots and Igor at 135 knots.  Let’s then see the occurrences of 110 knots+ for two hurricanes:

1950090412
1950090418
1950090500
1958092700
1958092706
1999091506

Only 6 time-instances in the best-track since 1950!

Here are the particulars for those events:

YEAR, #, BASIN, DATE, STAGE, LAT, LON, Wind Speed (knots)

1999 09  NA 1999091506 TS  28.20  -78.50 110
1999 10  NA 1999091506 TS  17.40  -47.90 110

1958 08  NA 1958092700 TS  31.70  -78.10 110
1958 09  NA 1958092700 TS  21.40  -61.20 115

1958 08  NA 1958092706 TS  32.40  -78.50 110
1958 09  NA 1958092706 TS  21.90  -61.30 110

1950 03  NA 1950090500 ET 39.70  -56.80 55
1950 04  NA 1950090500 TS  23.40  -67.70 140
1950 05  NA 1950090500 TS  27.90  -83.10 110

1950 03  NA 1950090418 TS  38.40  -58.10 65
1950 04  NA 1950090418 TS  22.90  -67.20 135
1950 05  NA 1950090418 TS  28.00  -83.80 110

1950 03  NA 1950090412 TS  37.80  -58.80 70
1950 04  NA 1950090412 TS  22.60  -66.80 135
1950 05  NA 1950090412 TS  27.40  -83.20 110

Early September 15, Julia was at 110 knots, Igor at 135 knots, and Karl at 40 knots.

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104 Responses to Hurricane Julia explodes — Atlantic has two coincident Category 4 hurricanes, very rare

  1. Ryan Maue says:

    The current 12-hour forecasts indicate a maximum intensity of 120 knots for Julia and 135 knots for Igor. Two coincident Category 4 hurricanes has not occurred since 1950.

    The only occurrence since 1900 happened on September 15, 1926 at 06Z with Hurricane 4 [115 knots] and the Great Miami Hurricane [120 knots].

    Thus, Igor and Julia will attain coincident intensities that are unprecedented.

  2. Anthony Watts says:

    This historical note might be worthy of a new thread.
    [yes, if the 5 AM AST advisory indicates strengthening, which I suspect it will]
    [going to ask Drudge to link, prepare for bandwidth]

    REPLY: Bandwidth is no issue, I have wordpress.com cloud computing behind WUWT, bring it!

    -Anthony

  3. the_Butcher says:

    Is this ‘Unbelievable’ because it has happened 3 times in the last 50 years (and who knows how many more times prior to that?)

  4. Steven Mosher says:

    where’s my plywood?

    oh wait Im in SF

    Cool Ryan you must be stoked!

    ryan: [i'm in Monterey enjoying the same fog banks as you]

  5. tallbloke says:

    It’s certainly been windy in the UK overnight. One of the plastic chairs on my patio was on its side this morning.

  6. Jay Currie says:

    And each one of these storms sucks heat out of the ocean and sends it on its way.

    Hmmm…let’s hope they are fish storms but I would stack an extra cord of firewood on the off chance that absent heat plus La Nina equals one very, very cold winter.

  7. maksimovich says:

    In the SH the Polar front jet has meandered up to around 40s a big antarctic blast into the mid latitudes.

    http://squall.sfsu.edu/gif/jetstream_sohem_00.gif

    ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…

  8. Natsman says:

    Something else for the warmista to blame on AGW…

  9. tonyb says:

    Ryan (excitedly) said;

    “Unbelievable: in our North Atlantic historical records, the forecast intensities of Igor and Julia during the next 12-24 hours will be unprecedented for coincident storms. The only time coincident Category 4+ occurred was in 1926 with Hurricane #4 and the Great Miami Hurricane (September 26 at 06:00 UTC).”

    You forgot to insert the words ‘short’ before the phrase ‘North Atlantic historical records’ and the words ‘observed’ as well. As Tom Fuller points out there is much better observation these days that goes together with better (official) recording of events.

    I suggest you read Hubert Lambs book ‘Historic Storms of the North Sea, British Isles and Northwest Europe’ which although not directly related to the area you describe nevertheless gives us a good insight into past storm activity.

    tonyb

    ryan: i’m well aware of the issues with the best-track, in the Atlantic, Pacific, and globally, i recall publishing something on it a few years ago… i wrote a whole dissertation on intense extratropical storms, and am aware of the Lambs book. Sometimes u need to just put the skepticism aside and simply look in wonder at what nature does all on its own…

  10. Anthony Watts says:

    Ryan I made a small formatting change, thanks for this post!

  11. tonyb says:

    Ryan

    Can you help me out here please? The Saffir Simpson scale for categorising Hurricanes was only introduced in 1970.
    http://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_Hurricane_Scale

    How do we therefore retrospectively categorise Hurricanes that existed prior to this new standard?

    ryan: simply according to the maximum recorded wind speed in the best-track database.

  12. I have no idea if this will come across or not and even if it does, you may not want to show it. If not just delete. This is a screen capture of my OSXplanet screen. I am not sure where the program gets its data from but storms are supposed to be updated every three hours.[no link or attachment . . . b.mod]

  13. Pete says:

    “ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…”

    Just checking I have this right. Are we expecting the jet stream to be sucked southerly by these storms, a bit like the “ox bow” loop that came southerly last winter?

    And is this a good model to follow that progression?

    http://www.stormsurfing.com/cgi/display_alt.cgi?a=glob_250

    If not, could someone recommend a similar animation type display. Thanks.

  14. berniel says:

    tonyb says:
    I suggest you read Hubert Lambs book ‘Historic Storms of the North Sea, British Isles and Northwest Europe’ …

    Oh yes, such good advice! Enjoy the wind in your hair right now, but whenever you feel sucked into the present, just open up a Hubert Lamb. It’s a pity the picture quality was so poor but the text rewards. That man is a giant of climate history obscured (as a sceptic) by the present scare of our supposed un-precendent-ed climate. He’s got the the grand scope, the big-picture-in-the-small in that marvellously British sober and nuanced story telling.

    Meanwhile in our small picture we have passed a SOI mile record of 2.5 years, and so with IOD still in neg, the deluge of the great southern land looks set to continue into our temperate spring and the southern flip of the tropical monsoon….
    http://www.bom.gov.au/climate/enso/

  15. Nice picture:
    http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/AIRMASS/FULLRESOLUTION/index.htm

    BTW
    The graphic file
    http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/AIRMASS/FULLRESOLUTION/IMAGESDisplay/l9NSHszWShFUy
    seen on the HTML page is NOT recognized by Firefox! (The name changes every hour.)

    Try to open the EUMETSAT files in Firefox and Opera browsers. Opera is able to open it without problem, Firefox see it as binary file and wants to save it. Probably the moronic Firefox comes from “Windows School of Doing Things in 1995″, where type of file is read from file extension instead of first few bytes of a file. Pathetic.

    Regards

  16. Follow up to EUMETSAT picture.

    There is a note above the picture window: Zoom: SHIFT key pressed and Drag on the image. Make use of it as the picture is much bigger than the image window on EUMETSAT html page.

  17. Steven mosher says:

    Ryan are you gunna stay up all night and watch storm tracks
    ryan: waiting for 5 AM AST advisories to update the post. i have work at Navy Lab in morn.

  18. kadaka (KD Knoebel) says:

    *ahem*

    1 Knot = 1 Nautical Mile per hour
    1 Nautical mile = 6076.12 ft. = 1852 m **
    1 Statute mile = 1760 yards = 5280 feet

    ** Definition: [n] a unit of length used in navigation; equivalent to the distance spanned by one minute of arc in latitude; 1,852 meters

    1) Also called: international nautical mile, air mile a unit of length, used esp. in navigation, equivalent to the average length of a minute of latitude, and corresponding to a latitude of 45°, i.e. 1852 m (6076.12 ft.)

    2) a former British unit of length equal to 1853.18 m (6080 ft.), which was replaced by the international nautical mile in 1970

    1 knot = 1.152 miles per hour = 1.85 kilometer per hour

    What is this stuff I’ve heard about the US going metric someday (there’s supposed to be a federal law about it) and metric is the system used in the sciences (like meteorology)? And now we’re using obscure seafarer units? How many fathoms deep do storms like this disturb the ocean?

  19. Caleb says:

    Measurements of AMO ought show the warm phase cools. Will the warm phase recover, or is this the beginning of the end for the AMO’s warm phase?

  20. John A says:

    All of that energy wasted on fish. Its a crime.

  21. Gareth says:

    Jay Currie said: “And each one of these storms sucks heat out of the ocean and sends it on its way.”

    Like a giant vortex tube.

  22. mike sphar says:

    Two Majors and a minor on the Wide screen . Its an amazing site. especially from the Eastern tip of Puerto Rico which is still quite close to the main feature. Next week back to the hurricane safe harbor of Northern Nevada.

  23. George Turner says:

    We are all doomed, doomed I say!

    Repent, and watch The Weather Channel

    <— read a book on the history on the history of The Weather Channel because watching The Weather Channel was just to exciting and stressful.

  24. George Turner says:

    [George, check out the guide to WUWT linked on the right side of this page near the top, check out formatting tips ~ ctm]

  25. phlogiston says:

    The USA MSM who are panic junkies at the best of times, will go completely hysterical over this. Expect hours on end of a ruggedly heroic Anderson Cooper with hair dramatically flapping in the wind. I wonder if they will evacuate the entire eastern US seaboard?

  26. kadaka (KD Knoebel) says:

    For Severe Weather Like This, You Should Have

    StormPredator

    Keep Track Of The Storms

    Receive Personalized Alerts

    Know When Severe Weather Is Approaching

    Think Of The Children!

    (This has been an unsolicited uncompensated recommendation by someone who just happens to think it’s a good thing to have.)

  27. dave38 says:

    OMG! It’s worse than we thought!!

  28. Jimmy Haigh says:

    Wot?! No warmists telling us all that they told us so yet?

  29. sleeper says:

    Wot?! No warmists telling us all that they told us so yet?

    Patience, Grasshopper.

  30. AGWpropogandist says:

    Oh no – it’s exactly as we thought. CAGW is spawning unprecedented storms which will only provide a temporary reprieve from the catastrophic warming to follow. Donations gratefully accepted.

  31. rbateman says:

    Jimmy Haigh says:
    September 15, 2010 at 2:45 am
    Wot?! No warmists telling us all that they told us so yet?

    The stampede will come soon enough, just as soon as they figure out where both will hit back to back.
    Have any 2 hurricanes ever hit the same place in rapid succession?

  32. Jose Suro says:

    Impressive! Patterns like this one are unsustainable though. It should change in a week or so, especially if moisture in the Indian Ocean keeps retreating east away from the East coast of Africa, as it is doing now. Tropical activity should shift to the Caribbean and (hopefully not) the southern Gulf of Mexico.

  33. PJB says:

    Great post, Ryan. The more you know, the better off you are. It is this kind of data that will help to demonstrate the reality of climate change and its sources of variation.

    Julia will run into some of Igor’s outflow so it may calm down shortly. Bermuda, OTOH, better batten down the hatches. Karl (Junior? lol) may yet be reborn in the GoM seeing how Hermine got charged up in that bathwater….

    What awaits us, this season, is a really active period to the end of October. We appreciate your work and getting it out there where we can access it. Kudos.

  34. Tom in Florida says:

    Are the wind speeds for Julia estimates from satellite photos and estimated pressure numbers or did a hurricane hunter aircraft actually fly in and measure them?

  35. Scott B says:

    @Tom in Florida:

    The wind speeds and pressures for Julia and Igor are just from satellite estimates. The hurricane hunters typically don’t fly further out than 60W to sample a storm. I think they do sometimes if the storm is threatening the Leeward Islands, but both of these storms should move well north of them.

  36. John says:

    While having two cat 4s simultaneously is almost without precedent in our records, let’s remind ourselves that since the satellite era, we now have the ability to identify hurricanes in the open ocean far from land, and to accurately classify their wind speed.

    Chris Landsea was lead author of an article about a year ago showing that there has been no upward trend in the number of hurricanes per decade hitting land, and that the decades which featured the largest numbers of major hurricanes were in the 1800s. I think WUWT even had a blog on the article. Those results contrasts with what you get with the satellite record, where there are upward trends in the last few decades. That upward trend is an artifact of the satellite record, where we now identify hurricanes which live and die hundreds of miles from land.

    So here is a question: if this were 1920 or 1950, would we know that either of these hurricanes was a class 4? If I had to guess, it is possible that in 1950 there would have been enough ships to have intersected Igor to say “yes”, but that isn’t a given. However, if Julia doesn’t stay a class 4 for very long, given where it currently is, far from shipping lanes and only recently a major hurricane, I would guess that we would never know that it was a class 4. If it degrades to a cat 1 in a few days and turns north well east of Bermuda, how possible is it that we might not have known of its existence?

    So perhaps it would be better to say that it is unprecedented — in the 30 or so years of the satellite record — to have two cat 4s in the N Atlantic.

    That said, it does appear to be consistent (there’s that dreaded word again) with the notion that in a warmer world there will be more powerful hurricanes.

    The counter argument, as Ryan Maue has said before, is that the total ACE in the N Hemisphere, and in the world, had NOT been trending upward, with the largest ACE amounts since 1979 occurring in 1993 and 1998. That isn’t so consistent with the idea of ever more powerful storms.

    Bottom line: two cat 4s at the same time is pretty impressive, but I don’t want to take any climate change implications just yet.

  37. tonyb says:

    I said

    “Can you help me out here please? The Saffir Simpson scale for categorising Hurricanes was only introduced in 1970.
    http://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_Hurricane_Scale

    How do we therefore retrospectively categorise Hurricanes that existed prior to this new standard?”

    ryan replied

    “: simply according to the maximum recorded wind speed in the best-track database.”

    Thanks for that Ryan. Would the maximum recorded wind speed recorded in say 1926 be using the same sensitivity of equipment and have been located in exactly the right place to have been able to accurately record a maxium wind speed?

    Sorry, I am not trying to be difficult, just trying to compare like with like.

    tonyb

  38. tonyb says:

    Ryan-my post at 5.43

    I should have said that I am aware of the Hurricane reanalyis programme and that many aspects of past climate are subject to revisionism

    http://www.nhc.noaa.gov/pdf/04landsea.pdf

    As with thermometers, or say rain gauges, unless you have the equipment in exactly the right place at the right time you might not be capturing the extremes accurately.

    When the nature of that equipment changes from the simple and local to the complex and universal the differences can become accentuated and can capture extremes outwith of the capabilties of the ‘old’ system to find.

    tonyb

  39. Ulric Lyons says:

    I would suggest keeping an eye on the solar wind velocity for changes in storm intensity and track. http://www.lmsal.com/solarsoft/latest_events/

  40. beng says:

    ********
    ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…
    ********

    The pulse of big blobs of tropical moisture & rain northward is often counteracted by a similarly large pulse of cold air southward to follow behind it. The passage of Hugo in VA years ago caused frosts in late Sept, well before the average first-frost.

  41. Ric Werme says:

    Yikes – I completely missed yesterday’s publication of Colorado State University Forecast of Atlantic Hurricane Activity from September 15 – September 28, 2010 and don’t have time to write my usual minimal guest post for it. Let’s just let it ride here. I’ll pay attention for the next one. Hmm, hey Anthony, this is about my usual guest post size – if you’d like I can fish out the “usual” graphic of storm activity tonight and we can give this its own post. Probably little point in it though.

    Lessee. Various quotes [comments in square brackets]:

    We expect that the next two weeks will be characterized by above-average amounts of activity (greater than 130 percent of climatology.) [The forecast quantity is ACE, Igor and Julia by themselves may meet the forecast.]

    The above-average forecast is due to a combination of factors. The primary factor is that we expect a very large amount of ACE to be generated by Igor. Current forecasts of Igor’s intensity from the National Hurricane Center indicate that this hurricane alone could generate enough ACE to approach the above-average definition. Julia is also expected to generate several ACE units as it tracks northwest across the Atlantic. Newly formed Karl could also help contribute modest amounts of ACE for the next several days. In addition, several of the global models are developing the next tropical wave moving off of the coast of Africa. The MJO is predicted to remain weak over the next two weeks, so we continue to primarily rely on currently-existing tropical cyclones and global model forecasts for this outlook. [Hey Richard Holle - have you ever looked at the correlation between the MJO and lunar tides? I seem to recall the MJO is about that timescale.]

    [Page 3 - nice graphics of the storm tracks for the forecast period and the updated activity graph I used on the previous forecast posts.]

    [From the five factors they look at:]
    3) Global Model Analysis
    The global models are fairly enthusiastic about developing the next wave off of the coast of Africa into a tropical cyclone. The GFS also hints at additional development possible in the 7-10 day timeframe. [Yep, those models sure can wax enthusiastic.]

    Verification of September 1 September 14, 2010 Forecast

    The two-week forecast of tropical cyclone activity from September 1 – September 14 looked to verify quite well until Hurricane Igor’s rapid intensification over the past couple of days. Activity at average levels (70-130%) was predicted, while observed activity was just outside the average category (approximately 140%) during the two-week period, due in large part to Igor’s copious ACE generation. As was the case during the last part of the August, most of the activity that occurred was in the tropical Atlantic’s Main Development Region. It appears that, in general, low-level winds were very favorable for storm formation during the two-week period. For example, low-level horizontal divergence was below-average, indicating increased low-level convergence which helps increase the likelihood of storm formation and intensification.

    Several storms contributed to ACE during the two-week period, with most of the ACE being generated by Hurricane Earl during the early part of the period and Hurricane Igor during the latter part of the period. The Madden-Julian Oscillation was of a fairly weak magnitude throughout the period and likely did not play much of a role in modulating TC activity (Figure B).

  42. Tom in Florida says:

    Scott B says:{September 15, 2010 at 5:09 am}
    “@Tom in Florida:
    The wind speeds and pressures for Julia and Igor are just from satellite estimates. ”

    Exactly, so when it is reported that this is the only the second time we’ve had two Cat 4 storms together, one must take it with a grain of salt. Prior to satellite coverage how would one know if this hadn’t happened more than once before, especially so far out in the Atlantic.

  43. Leon Brozyna says:

    With all the excitement focused on the rarity of two simultaneous major hurricanes (even if only fish storms), the footnotes are where all the action is:

    — Igor looks (so far) to be on track to slam Bermuda. Well, there go all those vacation/honeymoon plans. Let’s hope they only experience property damage.

    — TS (and maybe Hurricane when it hits) Karl will yet again do a number on the east coast of Mexico, already having experienced Alex and Hermine. Might not be majors, but that’s small comfort to the poor farmer in the hills watching his small abode float away in the floods these storms bring to Mexico’s inland regions.

  44. Marcus K says:

    Ryan,

    Thanks for the update. I’m also enjoying the pacific coastal fog while marveling at these Atlantic storms.

    Perhaps the lack of big storms in August increased the odds of multiple majors since the ATL basin has remained relatively free of upwelling. 2005 conditions were also ideal for development but the constant parade of storms created too much competition limiting the chances for concurrent majors. It reminds me of my storm chasing days when the best supercells seemed to occur close to sunset on the days when there was no activity anywhere during the afternoon.

    With tropical Atlantic SST anomalies near record highs and a developing La Nina, have you looked into the possibility that we could be setting up for a significant farm belt drought next year? I know there have been studies suggesting the dust bowl years were characterized by a large tropical SST differential between the Pacific and Atlantic basins (cool Pacific, warm Atlantic). Does the current situation and forecasts bear enough similarity to that of the 1930’s that we should be concerned?

    ryan: The SSTs are above average, but storms do not form due to the SST anomaly. It is likely that the atmospheric conditions of lower vertical shear allowed the African easterly waves to organize quicker than normal. When they come off of Africa with low-level circulations already (like midwestern US mesoscale convective systems) in La Nina years, they develop quickly. But the Cape Verde season is relatively short, and only a few more weeks of activity out there is normal.

    Similarity in climate — as with analogs in weather — is a risky business. You can never have the exact same climate conditions in terms of SST patterns, and then there is no guarantee that the nonlinear feedbacks will even operate in the same sign let alone the same way. Think of the radically different forecast tracks of a hurricane you get with different weather forecast models…

  45. Lance says:

    2 thoughts,

    yesterday they predicted that Julia would lose strength…hmmmm
    and if this curves the jet stream down to Eastern Canada/US, perhaps this will allow some of that unprecedented warmest 2010 temperatures into Western Canada Prairies…

  46. Douglas Dc says:

    To giant-heat sucking vacuums in the North Atlantic at the same time. As others have said this has probably happened before-but better detection is the operative word here…

  47. Dave F says:

    Wow, we should be glad for satellites. I wouldn’t want to sail through two of those back-to-back. Is it possible for hurricanes to join together?

    ryan: one can absorb another…but if they don’t “combine” they pinwheel around a center-of-mass just like our heavenly bodies in the solar system

  48. Pamela Gray says:

    Wouldn’t call this unprecedented unless qualified with “in the historical record”. It’s not like the pilgrims could see what was going on in the Atlantic by standing on the shore with a good eye-scope. Given the long history of the present location of the Atlantic, it stands to reason this has happened before.

  49. Pamela Gray says:

    I know the article includes that phrase, but commenter load tends to steer away from the original text and reverts to just the word “unprecedented” without the modifier.

    ryan: if you follow my musings elsewhere at climateaudit and on my personal page: tongue in cheek.

  50. DesertYote says:

    rbateman
    September 15, 2010 at 3:38 am

    “Have any 2 hurricanes ever hit the same place in rapid succession?”

    I seem to remember Florida getting slammed pretty hard by a couple right in a row during the mid 90s. I think one even went over the panhandle and hooked back for a second chance at destruction. I’m gonna havta google it when I get home tonight.

    BTW, Me and a few co-workers were talking about the possibility of a late season, with all of the major energy coming after the halfway point, but having three systems with two huge ones, and one of those nearing gigantic, just, well, blows me away.

    ryan: the past 60-years when taking account El Nino and La Nina: no discernible correlation between activity during the first half and the second half of the season. it’s a crapshoot…

  51. Ric Werme says:

    Lance says:
    September 15, 2010 at 7:10 am

    > yesterday they predicted that Julia would lose strength…hmmmm

    I’m not sure how it developed so much. From the satellite imagery Julia looks awfully ratty for a Cat-4 storm. Then again, most Cat-4s had several days to get their act together and develop a good symmetric “firing on all cylinders” pattern.

    BTW, in 2005 or so at one point there were 4 or 5 named storms, I think a record for the satellite era. Must’ve been a bunch of exhausted mets at the NHC that day.

    ryan: it’s fortunate that Julia is a fish storm — and the track of Igor was pretty well cemented days ago. It is a threat to Bermuda for sure. Karl is relatively weak compared to those monsters. With no imminent US landfall threats, the public warning machinery at NHC is on respite.

  52. Ric Werme says:

    rbateman says:
    September 15, 2010 at 3:38 am

    > Have any 2 hurricanes ever hit the same place in rapid succession?

    One year recently had two or three hit the Cape Hatteras area, I think one pair was separated by a week or so. No time to check today. Wikipedia’s annual summaries might be the easiest place to look.

  53. dp says:

    With all those wasted CPU cycles it’s no wonder we have global warming! Rather than:

    cat hurdat_1850_2009 | awk ‘($1 >= 1950 && $8 >= 100) {print $4}’ | sort -n -k 1,1 | uniq -d

    try:

    awk ‘($1 >= 1950 && $8 >= 100) {print $4}’ < hurdat_1850_2009 | sort -n -k 1,1 | uniq -d

    I keed! I keed!! Great story. It's amazing when Nature decides to churn the butter her way. I think too there's a bit of thumb on the scale in the wind speed claims as our ability to measure wind speed is vastly superior to anything we had in the 1950's and earlier, so maybe we should make absolute comparisons with a bit of caution. Surely we had no capability to observer rapid bursts in intensity as seen with this pair. Seen through our 1950's era lenses these bursts could easily have been missed.

  54. SSam says:

    Why does storm 12 of 1967 have such odd longitude values?

  55. Twiggy says:

    Yet again as with the last hurricane, Geo Sat shows Julia weakening and in no way a category 4, why does it take so long for NOAA to change the status? Even to my untrained eye one can see it wouldn’t sustain itself with the surrounding air patterns.

  56. DR says:

    Up up and away goes the heat; nature’s heat pump. Where will it go? Hmm.

    Given the current MEI values in the Pacific, PDO, AO and SOI, one has to wonder what this winter will look like in the NH. Wow.

    ryan: brutally cold…

  57. jorgekafkazar says:

    kadaka (KD Knoebel) says: “…What is this stuff I’ve heard about the US going metric someday (there’s supposed to be a federal law about it) and metric is the system used in the sciences (like meteorology)? And now we’re using obscure seafarer units? How many fathoms deep do storms like this disturb the ocean?”

    Most Americans can’t even pronounce kilometer properly, let alone use it as a measure of length.

  58. jorgekafkazar says:

    Leon Brozyna says: “…Might not be majors, but that’s small comfort to the poor farmer in the hills watching his small abode float away in the floods these storms bring to Mexico’s inland regions.”

    If you abide in an adobe abode, it won’t float.

  59. P Walker says:

    For what it’s worth , if the current models are correct Julia probably would have gone undectected a century ago regardless of her strength .

  60. TallDave says:

    I think if someone could tell us how many joules these swirling heat engines move and what parameters the amount of joules vary with (e.g. does a Cat 4 move twice as much heat as a Cat 2?) that would a very interesting WUWT post, particularly if you could relate this to the effect on global temps!

  61. Ryan Maue says:

    It is almost a certainty that prior to the satellite monitoring with geostationary imagers every half-hour ~1970, accurate 6-hourly fixes of hurricane intensity are biased low especially in the middle of the Atlantic and Eastern Atlantic.

    It is likely Julia would have been detected a century ago due to its proximity to the Cape Verde islands and the swell approaching. Its intensity may not have been known.

    There is also no evidence at this point to declare this event the result of AGW. Natural climate signals are still an order or two larger than the AGW signal. This is 2010 and not 2050 or 2100…

  62. J Solters says:

    Keep close watch on NHC kiddies. They’ll blow the ACE through the roof, especially with no hard evidence on mid-atlantic cyclones. At NHC bad is good. Worse is better. Don’t get your knickers in knots over their always high wind speed estimates. One mph estimate causes Cat. 3 to go to Cat. 4. et cet.

  63. BillD says:

    With floods in Tennesee and Pakistan, fires and droughts in Russia and record summer heat in 12 states in the USA (mostly southeast and mid-Atlantic), it seems that we are having a lot of extreme weather this year.

    ryanm: huh? you cite 2 floods, one fire, and a drought along with summer heat as examples of a planetary increase in extreme events? are you serious?

  64. peterhodges says:


    …the deluge of the great southern land looks set to continue into our temperate spring and the southern flip of the tropical monsoon….
    http://www.bom.gov.au/climate/enso/

    i hope this does not stall the filming of the new MadMax movie even longer

    someone down under tell George Miller we have lots dry brown post-apocalyptic desert up my way…;)

  65. Enneagram says:

    Which is the “stormspot” number then?

  66. kadaka (KD Knoebel) says:

    From: jorgekafkazar on September 15, 2010 at 9:26 am

    Most Americans can’t even pronounce kilometer properly, let alone use it as a measure of length.

    Some parts of the world are upset over how we can’t even properly spell kilometre. This includes countries so civilized their streets have parking metres.

  67. Enneagram says:

    Doubtless Prince Igor is an Orthodox and Julia is…undressed :-)

  68. Ryan Maue says:

    UPDATE: Awesome! The National Hurricane Center (Dennis Feltgen, Public Affairs Officer) issues the following Press release, which is picked up by a bunch of outlets: one example. No credit given to the research here at WWUT which they get WRONG! Phone call to Mr. Feltgen: “we looked this up in HURDAT ourselves this morning”.

    Quote of email, received at 11:15 AM eastern:

    With both hurricane Igor and Julia reaching Category 4 strength, NOAA’s National Hurricane Center reports these interesting facts:

    * Two category four hurricanes existing simultaneously in the Atlantic basin has occurred only one other time since 1900: September 16, 1926 (Hurricane #4 and the Great Miami Hurricane).
    * There are only three other incidents of two major hurricanes (Category 3 or higher) at the same time: 1950 (Dog & Easy), 1958 (Helene & Ilsa), and 1999 (Floyd & Gert).
    * Hurricane Julia is the most intense hurricane to be located so far in the Eastern North Atlantic.

    -Dennis

    Dennis Feltgen
    Public Affairs Officer
    Meteorologist
    NOAA Communications& External Affairs
    National Hurricane Center
    Miami, Fla.

    As you can see Point number 2 is demonstrably wrong based upon the analysis put forth in the rest of the post. There are MANY other instances of coincident major hurricanes SINCE 1950. I did not look prior to 1950, but there are more. Use the awk statement and change the year/date to 1850. Point number two should read:

    * There are only three other incidents of two major hurricanes (Category 3 or higher) at the same time of 110 knots intensity and higher since 1950: 1950 (Dog & Easy), 1958 (Helene & Ilsa), and 1999 (Floyd & Gert).

    oops…perhaps a clarification

  69. Enneagram says:

    kadaka (KD Knoebel) says:
    September 15, 2010 at 11:17 am

    That because of that unnatural metric system concocted back in the French Revolution to attain a secular state and to alienate people from nature cycles or from anything which could lead to knowledge which from then on was reserved only for Kool-Aid drinkers, however they still don’t get it. (BTW, not our fault)

  70. George E. Smith says:

    “”” kadaka (KD Knoebel) says:
    September 15, 2010 at 1:40 am
    *ahem*

    1 Knot = 1 Nautical Mile per hour
    1 Nautical mile = 6076.12 ft. = 1852 m **
    1 Statute mile = 1760 yards = 5280 feet

    ** Definition: [n] a unit of length used in navigation; equivalent to the distance spanned by one minute of arc in latitude; 1,852 meters

    1) Also called: international nautical mile, air mile a unit of length, used esp. in navigation, equivalent to the average length of a minute of latitude, and corresponding to a latitude of 45°, i.e. 1852 m (6076.12 ft.)

    2) a former British unit of length equal to 1853.18 m (6080 ft.), which was replaced by the international nautical mile in 1970

    1 knot = 1.152 miles per hour = 1.85 kilometer per hour

    What is this stuff I’ve heard about the US going metric someday (there’s supposed to be a federal law about it) and metric is the system used in the sciences (like meteorology)? And now we’re using obscure seafarer units? How many fathoms deep do storms like this disturb the ocean? “”””

    Well kadaka; I believe you forgot to add that one Nautical mile is also 1000 Fathoms, so strictly speaking a fathom is 1.852 metres or 6.07612 ft. Well at least it used to be; but they keep dicking around with the units; it’s almost as bad as the Pyramid Inch; that is used to read the history of the world in the Great Pyramid.

    But on a more important note; that sneaky Julia is staying well away from Igor’s now cold aftermath, so she can soak up her own BTUs.

    Ah at last the media worrywarts can revel in the coming disaster.

  71. George E. Smith says:

    “”” kadaka (KD Knoebel) says:
    September 15, 2010 at 11:17 am
    From: jorgekafkazar on September 15, 2010 at 9:26 am

    Most Americans can’t even pronounce kilometer properly, let alone use it as a measure of length.

    Some parts of the world are upset over how we can’t even properly spell kilometre. This includes countries so civilized their streets have parking metres. “””

    Well I dunno how Jorge spells/pronounces it; but I for one am not among the Kill Ommita crowd; simply refuse to be. The metre (meter) is the IS unit of length and k for kilo (keylow) is the approved prefix for 1000 of; so that means it should be keylowmeter; but we Kiwis speak kinda lazy, so I’m sure that I say kil-uh-meter sans hyphens. And I don’t buy into the parking metre bit at all; for that matter I don’t buy into the parking meter either. I simply refuse to go any place where I would have to feed coins into some bandit machine for the privilege of parking on a public street or place.
    So if you are a shop owner; put up parking meters if you don’t want me to shop at your place; because I won’t if you do.

  72. atmoaggie says:

    Good stuff, Ryan! Thanks for hitting the t-list so I didn’t miss it.

    So what went right with Julia to allow her to attain such stature? Seems as though she is right there at, or maybe slightly beyond, the max potential intensity, which happens very rarely.

    Also curious as to what you’re doing at NRL. Going to fix their N-GFDL or COAMPS-Hurricane?

    ryan: the SSTs are probably some of the lowest seen to support a Category 4 hurricane. I suspect the largest positive influence on the MPI would be the stratospheric temperatures much cooler than seen elsewhere in the tropics.

    I work on 5-7 day predictability issues with NOGAPS and comparisons with other NWP models like ECMWF and GFS.

  73. David L. says:

    Much worse than I ever thought. I’m surprised that 2/3 of the previous occurances were back in the 1950’s. Had Globull Warnings kicked in by then? If not, what caused this event in the 1950’s? And do we know if this happened at all in the 1450’s, or 1350’s or even 1250’s?

  74. Jaye Bass says:

    ryan: …but if they don’t “combine” they pinwheel around a center-of-mass just like our heavenly bodies in the solar system

    That would make for an interesting satellite loop.

  75. So I was wrong about a (complete) lull in hurricane production from Sept 3rd through the 20th, (crow are fattening up in the cage) But what about the possibility of a continued increased surge in strong hurricane production after the 21st? (If what we have now is a slowdown from the max potential?)

    I am still awaiting the rest of the season, popcorn and BBQ crow in hand, [Is KFC an acceptable substitute, if this goes on a long time?];)

    Ryan talks about the cold surge post Igor as the moon goes from Maximum South to across the equator, and the air pumped into the arctic, sends down the air mass parked there now, into your gardens.

    As for the coming winter in the USA, I have data base for that, you might want of look at the analog forecast on my site, click on the calendar icon and fast fwd up to November, then select Lows (or snowfall) then rapidly scan forward by [next] days for several months through the winters of 2010-11, 2011-12, and 2012-13, for S&Grins.

    Not too late to place your cities road salt orders yet?

  76. Pascvaks says:

    Ref – maksimovich says:
    September 15, 2010 at 12:23 am
    “In the SH the Polar front jet has meandered up to around 40s a big antarctic blast into the mid latitudes.
    http://squall.sfsu.edu/gif/jetstream_sohem_00.gif
    ryan: “just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…”
    ___________________________
    Sounds like glacial periods are fraught with hurricanes sucking the jets toward the equator, dumping scads of precip all over the place and making glaciers advance toward NYC and Rio. Is this the beginning of the end? For some reason, I guess it was all that ice, I thought glacial periods had more hurricanes that we do now. Cold AND windy AND wet! Hummmmm……

  77. CO2 Insanity says:

    Arctic blast? It’s been close to being an “unprecedentedly” cold summer in San Francisco now we’re going to freeze? I’m stocking up on “robust” long underwear along with an “unprecedentedly” warm down jacket. Damn global warming. I suppose next summer I’ll have to the heater on.
    [ryan: tell me about it. i am expecting polar bears to be infiltrating Monterey Bay this winter]

  78. Enneagram says:

    [Is KFC an acceptable substitute, if this goes on a long time?];)
    No, too oily, good to make eco-fuel.

  79. kadaka (KD Knoebel) says:

    Excerpts from: George E. Smith on September 15, 2010 at 12:00 pm

    The metre (meter) is the IS unit of length and k for kilo (keylow) is the approved prefix for 1000 of; so that means it should be keylowmeter; but we Kiwis speak kinda lazy, so I’m sure that I say kil-uh-meter sans hyphens.

    And here I thought the debate was between kilo-meh-ter or kilo-meet-er. Perhaps a combination possibly yielding “…kill ah meet ‘er south of town…” should be avoided due to potential misinterpretation if overheard.

    And I don’t buy into the parking metre bit at all; for that matter I don’t buy into the parking meter either. I simply refuse to go any place where I would have to feed coins into some bandit machine for the privilege of parking on a public street or place.

    That was a local news story last night. The City of Scranton installed 76 parking meters outside a General Dynamics plant. So the workers simply parked elsewhere. After roughly a month the meters haven’t garnered more than one dollar in revenue, of which at least part of that was at least one TV reporter plugging a meter for a previous story.

    A Scranton City Council member says maybe they should talk to General Dynamics about an alternate plan such as parking permits. I think General Dynamics is considering moving somewhere they can have their own parking lot and not have their workers get specifically targeted.

  80. Enneagram says:

    Richard Holle says:
    September 15, 2010 at 12:31 pm
    You could be still right; if so that couple would degrade.

  81. AndyW says:

    Looking forward to Ryan’s next Ace update for the season after this episode.

    I can’t imagine two hurricanes of such magnitude would last for so long following each other, the first one produces shear and also sucks the energy out of the ocean?

    Andy

    [ryan: http://www.coaps.fsu.edu/~maue/tropical ]

  82. Michael D Smith says:

    editorial comment:

    But Igor and Julia just are not major hurricanes

    I think you mean “are not just”, since they are major hurricanes.
    [ryan: true enough, fixed up]

  83. Ric Werme says:

    jorgekafkazar says:
    September 15, 2010 at 9:26 am

    kadaka (KD Knoebel) says: “…What is this stuff I’ve heard about the US going metric someday (there’s supposed to be a federal law about it) and metric is the system used in the sciences (like meteorology)? And now we’re using obscure seafarer units? How many fathoms deep do storms like this disturb the ocean?”

    Well, there is the Metric Act of 1866 http://lamar.colostate.edu/~hillger/laws/metric-act.html that authorized using SI units, and then the Metric Conversion Act of 1975 (Public Law 94-168) passed by Congress. The Metric Act established the U.S. Metric Board to coordinate and plan the increasing use and voluntary conversion to the metric system. However, the Metric Act was devoid of any target dates for metric conversion. http://lamar.colostate.edu/~hillger/dates.htm

    Aha – here’s some progress:

    2007 January 08
    “Metric Moon” press release: NASA has decided to use metric units for all operations on the lunar surface when it returns to the Moon. See the NASA announcement. NASA’s Constellation Program is to be metric, according to a Program Management Directive issued on 19 December 2007, with the metric system as the “primary system of measure” for the Constellation Program, Projects, Systems, and Mission.

    Of course, that project was canceled or something like that to buy General Motors instead.

  84. kadaka (KD Knoebel) says:

    Re: Ric Werme on September 15, 2010 at 2:38 pm

    There was a firm transition date at one point. Just a few years ago (at least it feels that way) there was a network TV news report about the upcoming transition. I mainly remember the reporter showing a dual-system speed limit sign, mph and kph, saying how these will be going up soon for the transition period, after which there would only be metric signs.

    Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t.

  85. Earle Williams says:

    What’s so hard to pronounce?

    klik

    There! :-)

  86. George E. Smith says:

    “”” kadaka (KD Knoebel) says:
    September 15, 2010 at 1:19 pm
    Excerpts from: George E. Smith on September 15, 2010 at 12:00 pm

    The metre (meter) is the IS unit of length and k for kilo (keylow) is the approved prefix for 1000 of; so that means it should be keylowmeter; but we Kiwis speak kinda lazy, so I’m sure that I say kil-uh-meter sans hyphens.

    And here I thought the debate was between kilo-meh-ter or kilo-meet-er. “”

    Well KD, I’m good for either of yours; it was the k-lomuhtuh that I would like to see squished.

  87. KLA says:

    Well,

    According to my sources, America IS going metric: Inch by Inch.

  88. SSam says:

    kadaka (KD Knoebel) says:
    “…Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t…”

    As soon as they run out of ways to attach pork to the other rules they will take care of that pretty quickly.

  89. rbateman says:

    Some couple of decades ago, when you bought a new car, it had the Speedometer in Mph and Kph.
    They disappeared after a while. 55 Mph is 88 Kph if I remember correctly.
    A School Zone is going to be 40 Kph/25 Mph, and the fastest freeway speed will be 112 Kph/70 Mph.
    Won’t this be fun?

  90. kadaka (KD Knoebel) says:

    SSam said on September 15, 2010 at 4:08 pm

    kadaka (KD Knoebel) says:
    “…Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t…”

    As soon as they run out of ways to attach pork to the other rules they will take care of that pretty quickly.

    More confirmation the United States will never go metric.

  91. sky says:

    Question for Ryan:

    Since satellite sensing of Mid-Atlantic hurricane wind speeds has been available only for the last ~30 years, how certain can we be of the UNPRECEDENTED simultaneous occurrence of two CAT4s?

    [ryan: 1-occurrence in the last 30-years suggests that the event is rare. This could be teased out by looking at the date/times when two simultaneous hurricanes exist and put an uncertainty bound on each’s intensity. The word “unprecedented” is a tongue-in-cheek reference to the sensationalism of climate/weather occurrence reporting in the media. Grain of salt considering the quality of our hurricane records in the past…

  92. Gerry says:

    The storms this year don’t seem to be following the historic tracks. If the weather prognosticators have the hurricane prediction thing so well in hand, where are the predictions that these storms will form and intensify so far east and turn north so far out to sea?

    Gerry

    [ryan: they have no skill in predicting the season's track characteristics in advance, let alone 7-days ahead of time]

  93. Caleb says:

    I’m increasingly convinced these monsters are a nice, neat safety-valve for the warm AMO. Or, in other words, a “negative feedback” for “warming.”

    With so much heat sucked out of the Eastern Tropical North Atlantic, it will be interesting to see if the end of the season shows storms developing in the Caribbean, Gulf of Mexico, off the coast of Florida, and generally in the Western Tropical North Atlantic.

    If that happens the only warm anomalies left will be to the north. Interestingly, the blocking pattern being stuck over Russia for so long this summer seems to have led to off-shore winds in certain parts of the Siberian Arctic coast. While this has pushed warm surface waters (and melting) towards the poles, it seems to have brought about upwelling and cold anomalies along the Siberian coast, where I don’t recall seeing them before.

    The warm AMO may not be over, but we seem to be entering a colder phase of the warm phase.

  94. Gail Combs says:

    #
    #
    Richard Holle says:
    September 15, 2010 at 12:31 pm

    So I was wrong about a (complete) lull in hurricane production from Sept 3rd through the 20th, (crow are fattening up in the cage) But what about the possibility of a continued increased surge in strong hurricane production after the 21st? (If what we have now is a slowdown from the max potential?)

    I am still awaiting the rest of the season, popcorn and BBQ crow in hand, [Is KFC an acceptable substitute, if this goes on a long time?];)….
    _________________________________________________________

    BBQ crow has got to be more tasty than the deep fried seagull they used to serve in the company cafeteria. The seagulls perched on the company roof after resting from raiding the garbage dump nearby. Parking spaces along the line of flight were left for unwary visitors….

  95. Gail Combs says:

    kadaka (KD Knoebel) says:
    September 15, 2010 at 3:07 pm

    Re: Ric Werme on September 15, 2010 at 2:38 pm

    There was a firm transition date at one point….

    Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t.
    _________________________________
    Given that many states are facing bankruptcy (or at least high Deficits) I do no think the conversion to metric is a high priority.

    http://www.zerohedge.com/article/32-states-now-officially-bankrupt-378-billion-borrowed-treasury-fund-unemployment-ca-mi-ny-w

  96. NovaReason says:

    Question for the more meteorology inclined.

    Looking at the 5-day forecasts for both storms, the projected turn back Westward for Igor is reasonable, but Julia looks like it’s going to break her damn neck turning around. Do the forecasts suppose that Igor is going to push Julia back, and if so, why won’t the same effect push Igor a little more Eastward? I noticed that they still have it going right over Bermuda, even though it seems to have stayed on a more southerly route than originally anticipated (going back 2 days on that, haven’t been tracking Igor as carefully since all the forecasts show it going way out to sea and not even making it to the Continental US).

  97. NovaReason says:

    rbateman says:
    September 15, 2010 at 4:21 pm
    Some couple of decades ago, when you bought a new car, it had the Speedometer in Mph and Kph.
    They disappeared after a while. 55 Mph is 88 Kph if I remember correctly.
    A School Zone is going to be 40 Kph/25 Mph, and the fastest freeway speed will be 112 Kph/70 Mph.
    Won’t this be fun?

    My 2008 has this cool option where I can swap all of the metrics on it from US to Metric. I swapped it at one point thinking it would only change things like my Temp (on the display). Surprised me to find out it changes the speedometer to kmph, too. I left it switched one time for my gf and it freaked her out. (barely going 30mph, looks like almost 50).

  98. Wayne Delbeke says:

    ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…
    ——————————————————
    Too late – frost already on the way, forecast is for frost for the next week in central Alberta, 6 below Celsius for Saturday night.

  99. Wayne Delbeke says:

    George E. Smith says:
    September 15, 2010 at 11:47 am
    Units
    ++++++++++++++++++++++++++++++
    Ah yes, metric – divide by 10, but it is so interesting to know how many Firkins there are in a Hogshead and how many Hogsheads are in a barrel and the variance depending on the contents … and whether we are talking US or Imperial measurements or usage.

  100. Brian H says:

    Been there, done that, in Canada decades ago. The transition was real fun. Now metric only. But I’m in my 60s, so I still translate most metric back into British.

    In the process, I’ve learned a few interesting things about that creaky old system. An ounce of water weighs about an ounce. A British gallon weighs 10 lbs. (160 oz.) A pint (16 oz) weighs about a pound.

    I’m sure there are more convenient matchings buried in there!

  101. Walter Dnes says:

    DR says:
    > September 15, 2010 at 9:19 am

    > Given the current MEI values in the Pacific, PDO, AO and SOI,
    > one has to wonder what this winter will look like in the NH. Wow.

    > ryan: brutally cold…

    Note; the following are experimental forecasts, not the official product…

    See http://www.cpc.noaa.gov/products/people/wwang/cfs_fcst/images3/glbT2mMon.gif for a monthly forecast. Currently Sep-to-Feb, changing to Oct-to-Mar sometime in the next 10 days or so.

    Remember January and February 2008? For comparison, see that archived forecast at http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst_history/200709/images/glbT2mMon.gif

  102. aurbo says:

    I was hoping to wait a few weeks to do a thorough study on inter-seasonal comparison of HU (Hurricane) and TS (Tropical Storm) winds and pressures, but the hoopla given this current episode where NOAA is reporting on the rarity of having a coincident pair of storms simultaneously reporting Cat-4 winds (Category 4: Winds ranging between 114-135 kts or 131-155 mph) prompts me to post some relevant information now.

    The criteria for reporting the maximum sustained wind (as opposed to wind gusts) differs from one global region to another. The US uses a one minute average to determine the maximum sustained wind. In TS or HU observations, the max sustained wind is determined by taking a 10 minute average multiplied by 0.88. The “surface” wind is assumed to be a height of 10 m above the surface. Even in dropsonde measurements where winds are measured down to splash, the lowest 10 m is ignored. The reason for this is that closer to the water/ground it is assumed that frictional effects will sharply reduce actual wind speeds.

    In the past, before satellites and sophisticated remote sensing techniques from aircraft were available, most of the actual wind observations came from instrumented land sites or ships of opportunity [in some cases when ships got caught in the inner circulation, ships of inopportunity]. Many of these ship reports were from wind instrumentation mounted on the deck or masts. Other means such as the Beaufort Scale used eyeball observations of the state of the sea.

    In the modern era, on site ship reports have declined enormously, mainly because unlike the earlier generations, current warnings combined with modern communication have kept most craft from being caught anywhere near the central circulation.

    Today, most of these observations of wind and pressure are provided by or deduced from satellite platforms, some using active data and many using passive data. All require some level of processing and analysis. Another source of what is usually considered more reliable data come from reconnaissance aircraft. These aircraft carry a variety of platforms including manmade (eyeball) observations, doppler radar, standard aircraft wind and temperature probes, SFMR (Stepped Frequency Microwave Radiometry) for estimating surface winds and dropsondes (compact instrumented packages released from the aircraft and equipped with GPS to report their precise location and parachutes to slow their descent to the surface) which observe temperatures, pressures and humidity.

    As of this writing none of the observations of high winds, temperatures and central pressures for either HU Igor or HU Julia have come from aircraft or surface-based observations. An AF Recon flight is scheduled to be in Igor tomorrow (Thursday).

    So, up until now essentially all of the reports of maximum winds and lowest surface pressure have been derived from satellite data and none have been supported by ground truth. One would hope that these estimates are reasonably conservative, but in this age of apparently acceptable hyperbole this may be wishful thinking.

    Now here is the most important factor: In regard to winds, whatever they are measuring it is not sustained maximum winds. A valid sustained maximum wind is one that is measured from a fixed location over a particular time interval (or that can be referenced to a fixed location say from a platform moving at a known velocity independent of the ambient wind). Even with dropsondes, one can tell exactly how fast the instrument package is moving, but not what the particular wind speed would be if it were anchored to a fixed location.

    Until at least 1996, the record observed “surface” wind speed was in excess of 220 mph with a peak wind (gust?) of 231 mph (372 km/hr) at 1:21PM on April 12, 1934 measured by a heated 3-cup Robinson type anemometer with a human observer on site at Mt Washington NH. Robinson anemometers actually record the distance the cups travel in their rotation about a fixed axis, and on some models the distance is displayed in miles and fractions thereof much like an automobile odometer. Thus, what they are reading is the miles of air moving past the instrument which when divided by 24 gives a true daily average wind speed. Similarly when recorded each hour the data gives a true average wind in mph. Thus one can obtain a true average wind speed for any desired time interval by simple division.

    The problem with the remote wind measurements in Tropical storms is that in the absence of a fixed observation point where the wind is actually occurring, it’s nearly impossible to tell whether one is measuring winds or wind gusts. Doppler microwave devices are often gated to observe maximum velocities. These are usually instantaneous wind speeds. If a gust front were approaching a Doppler equipped radar it could provide a fairly precise speed of the gust, but the duration at any point along the path of the gust might only be a few seconds, much too short a time to determine a sustained wind. All of this strongly suggests that the determination of maximum sustained winds in a TS or HU are very likely to be maximum gusts and their relation to the true max wind would depend on the density of the gust pattern and the cross-section across which the instrument is observing.

    The determination of whether a record max wind is a gust or a sustained wind might be considered a difference without a distinction except that there are very real differences in the impact of such winds upon fixed objects in the path of the wind. The force of the wind per unit area on a stationary surface normal to the wind is proportional to 4 times the speed of the wind. The power of the wind (the force per unit time) is proportional to 8 times the wind speed. Wind gusts, by definition, have much lower power densities than sustained winds. That’s why it’s importance to know what the real sustained maximum winds are and not just the gusts.

    The nearest things to a stationary observation platform are anchored buoys. These can, and do report sustained winds and gusts quite accurately. The only problem is that one can’t easily plan on having these buoys in the path of a storm.
    BTW, there are some very interesting wind and SLP observations that were taken near (but not exactly in) the center of HU Earl when it passed to the S and E of New England about a week ago.

    One final point: Most historical wind data for TSs and HUs up until the past few decades were obtained from fixed or relatively stationary platforms where the integrated wind over time periods from 1 minute to 10 minutes could reliably be determined. Except for well instrumented and maintained buoys, most of today’s remotely observed winds cannot be accurately compared to the earlier historic records and thus by incorporating such data uncritically, the climate record is being corrupted.

  103. Chris Knight says:

    Brian H says:
    September 15, 2010 at 8:42 pm

    An ounce of water weighs about an ounce. A British gallon weighs 10 lbs. (160 oz.) A pint (16 oz) weighs about a pound.

    Can’t be right, Brian. The British memorial rhyme goes:

    “A pint of pure water weighs a pound and a quarter.”

    Indeed there are 20 fluid oz in a British pint.

    I once heard Lucille Ball (IIRC) repeating the following:

    “A pint of water weighs a pound, and that’s the same the whole world round!”

    So I know that’s not true.

  104. AJB says:

    Chris Knight says:
    September 16, 2010 at 1:35 am

    A fluid ounce is a capacity measurement and has nothing to do with weight.

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