Global warming and the frequency of intense Atlantic hurricanes: model results

By: Dr. Jeff Masters , 1:37 PM GMT on April 05, 2010

Could global warming increase wind shear over the Atlantic, potentially leading to a decrease in the frequency of Atlantic hurricanes? There is a growing consensus among hurricane scientists that this is indeed quite possible. Two recent studies, by Zhao et al. (2009), "Simulations of Global Hurricane Climatology, Interannual Variability, and Response to Global Warming Using a 50-km Resolution GCM", and by Knutson et al. (2008), "Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions", found that global warming might increase wind shear over the Atlantic by the end of the century, resulting in a decrease in the number of Atlantic hurricanes. For example, the second study took 18 relatively coarse (>60 km grid size) models used to formulate the 2007 IPCC climate report, and "downscaled" them using a higher-resolution (18 km grid size) model called ZETAC that was able to successfully simulate the frequencies of hurricanes over the past 50 years. When the 18 km ZETAC model was driven using the climate conditions we expect in 2100, as output by the 18 IPCC models, the authors found that a reduction of Atlantic tropical storms by 27% and hurricanes by 18% by the end of the century resulted. An important reason that their model predicted a decrease in the frequency of Atlantic hurricanes was due to a predicted increase in wind shear. As I explain in my wind shear tutorial, a large change of wind speed with height over a hurricane creates a shearing force that tends to tear the storm apart. The amount of wind shear is critical in determining whether a hurricane can form or survive.

Figure 1. Top: predicted change by 2100 in wind shear (in meters per second per degree C of warming--multiply by two to get mph) as predicted by summing the predictions of 18 climate models. Bottom: The number of models that predict the effect shown in the top image. The dots show the locations where tropical storms formed between 1981-2005. The box indicates a region of frequent hurricane formation where wind shear is not predicted to change much. Image credit: Geophysical Research Letters, "Increased Tropical Atlantic Wind Shear in Model Projections of Global Warming", by Vecchi and Soden, 2007.

Since the Knutson et al. study using the 18 km resolution ZETAC model was not detailed enough to look at what might happen to major Category 3 and stronger hurricanes, a new study using a higher resolution model was needed. This was done by a team of modelers led by Dr. Morris Bender of NOAA's GFDL laboratory, who published their results in Science in February. The authors used the GFDL hurricane model--the model that has been our best-performing operation hurricane track forecasting model over the past five years--to perform their study. The GFDL hurricane model runs at a resolution of 9 km, which is detailed enough to make accurate simulations of major hurricanes. The researchers did a double downscaling study, where they first took the forecast atmospheric and oceanic conditions at generated by the coarse (>60 km grid) IPCC models, used these data to initialize the finer resolution 18 km ZETAC model, then used the output from the ZETAC model to initialize the high-resolution GFDL hurricane model. The final results of this "double downscaling" study suggest that although the total number of hurricanes is expected to decrease by the end of the century, we should expect an increase of 81% in the number of Category 4 and 5 storms in the Atlantic. This trend should not be clearly detectable until about 60 years from now, given a scenario in which CO2 doubles by 2100. The authors say that their model predicts that there should already have been a 20% increase in the number of Category 4 and 5 storms since the 1940s, given the approximate 0.5°C warming of the tropical Atlantic during that period. This trend is too small to be detectable, given the high natural variability and the difficulty we've had accurately measuring the exact strength of intense hurricanes before the 1980s.The region of the Atlantic expected to see the greatest increase in Category 4 and 5 storms by the year 2100 is over the Bahama Islands (Figure 2), since wind shear is not expected to increase in this region, and sea surface temperatures and atmospheric instability are expected to increase there.

The net effect of a decrease in total number of hurricanes but an increase in the strongest hurricanes should cause an increase in U.S. hurricane damages of about 30% by the end of the century, the authors compute, assuming that hurricane damages behave as they did during the past century. Over the past century, Category 4 and 5 hurricanes made up only 6% of all U.S. landfalls, but accounted for 48% of all U.S. damage (if normalized to account for increases in U.S. population and wealth, Pielke et al., 2008.)

Figure 2. Expected change in Atlantic Category 4 and 5 hurricanes per decade expected by the year 2100, according to the Science paper by Bender et al. (2010).

Commentary
These results seem reasonable, since the models in question have been successfully been able to simulate the behavior of hurricanes over the past 50 years. However, the uncertainties are high and lot more research needs to be done before we can be confident of the results. Not all of the IPCC models predict an increase in wind shear over the tropical Atlantic by 2100, so the increase in Category 4 and 5 hurricanes could be much greater. Also, the GFDL model was observed to under-predict the strength of intense hurricanes in the current climate, so it may not be creating enough Category 4 and 5 hurricanes in the future climate of 2100. On the other hand, IPCC models such as the UKMO-HadCM3 predict a very large increase in wind shear, leading to a drastic reduction in all hurricanes in the Atlantic by 2100, including Category 4 and 5 storms. So Category 4 and 5 hurricane frequency could easily be much greater or much less than the 81% increase by 2100 found by Bender et al.

The estimates of a 30% increase in hurricane damages by 2100 may be considerably too low, since this estimate assumes that sea level rise will continue at the same pace as was observed in the 20th century. Sea level rise has accelerated since the 1990s, and it is likely that this century we will see much more than than the 7 inches of global sea level rise that was observed last century. Higher sea level rise rates will sharply increase the damages due to storm surge, which account for a large amount of the damage from intense Category 4 and 5 hurricanes.

Keep in mind that while a 30% in hurricane damage by the end of the century is significant, this will not be the main reason hurricane damages will increase this century. Hurricane damages are currently doubling every ten years, according to Pielke et al., 2008. This is primarily due to the increasing population along the coast and increased wealth of the population. The authors theorize that the Great Miami Hurricane of 1926, a Category 4 monster that made a direct hit on Miami Beach, would have caused about \$150 billion in damage had it hit in 2005. By 2015, the authors expect the same hurricane would do \$300 billion in damage. This number would increase to \$600 billion by 2025 (though I think it is likely that the recent recession may delay this damage total a few years into the future.) It is essential that we limit coastal development in vulnerable coastal areas, particularly along barrier islands, to reduce some of the astronomical price tags hurricanes are going to be causing. Adoption and enforcement of strict building standards is also a must.

The authors of the GFDL hurricane model study have put together a nice web page with links to the paper and some detailed non-technical explanations of the paper.

References
Bender et al., 2010, "Modeled Impact of Anthropogenic Warming on the Frequency of Intense Atlantic Hurricanes", Science, 22 January 2010: Vol. 327. no. 5964, pp. 454 - 458 DOI: 10.1126/science.1180568.

Vecchi, G.A., B.J. Soden, A.T. Wittenberg, I.M. Held, A. Leetmaa, and M.J. Harrison, 2006, "Weakening of tropical Pacific atmospheric circulation due to anthropogenic forcing", Nature, 441(7089), 73-76.

Vecchi, G.A., and B.J. Soden, 2007, "Increased Tropical Atlantic Wind Shear in Model Projections of Global Warming", Geophysical Research Letters, 34, L08702, doi:10.1029/2006GL028905, 2007.

Jeff Masters

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405. bappit
 402Spring has sprung.
404. hydrus
 Quoting WaterWitch11:hey hydrus What happened to spring? 89 degrees here on the Cumberland Plateau today.
403. WaterWitch11
 Quoting hydrus: Wuzup WaterWitch.hey hydrus
Member Since: August 11, 2008 Posts: 3 Comments: 1988
402. Bordonaro
 Wow, look at all these storm reports:
Member Since: August 25, 2009 Posts: 20 Comments: 6785
401. winter123
 Going back to ike discussion... 2008 was crazy because I think every hurricane that was poised to hit the US changed course to go over cuba, which disrupted their circulations enough that it could never get fully "right" again.And I can never forget this (VIDEO IS RELEVANT... since i've gotten banned for stuff like this in the past):Just a gut feeling, but based off the water temps east of the Antilles, and the (supposedly) declining El Nino, I have a feeling we'll have a lot of long trackers like this in 2010.
400. hydrus
 Quoting StormW:Ouch! In post # 384 you see trouble brewing. Would you please elaborate further if you have time?
398. hydrus
 Quoting WaterWitch11:my concern is if the pattern from october continues is that we will see another strong one somewhere other than the us west coast and then another moderate one in the la area. la area one would be nw. my 2 cents!!good evening everyone! Wuzup WaterWitch.
397. hydrus
 Quoting StormW:LOL! 1967 Cutlass, 1990 Nissan Sentra, 1991 Eagle Talon. The Cutlass fell victim to Tropical Storm Bob in 1985. A lot of rain fell to fast while I was at sea. whine....
395. hydrus
 Quoting StormW:Freshwater flooding has been listed as the number one storm killer. Fresh water flooding has not killed me yet. But it has killed a few of my vehicles.
394. WaterWitch11
 Quoting KEEPEROFTHEGATE:maybe if it follows the pattern next big shaker just ne of la sw offshore of san fran but hey what do i know just the pattern is sa/cen america/west coast then cen america now s america next will be back to west coast or cen america up near wash/bc been quiet maybe some type of release there too soonmy concern is if the pattern from october continues is that we will see another strong one somewhere other than the us west coast and then another moderate one in the la area. la area one would be nw. my 2 cents!!good evening everyone!
Member Since: August 11, 2008 Posts: 3 Comments: 1988
393. hydrus
 Quoting bappit:379"Because storm surge-induced flooding has killed more people in the United States in hurricanes than all other hurricane-related threats (freshwater flooding, winds, and tornadoes) combined since 1900 the National Oceanic and Atmospheric Administration is working to enhance the analysis and prediction of storm surge."Seems not too long ago people were saying that freshwater flooding killed the most people. I think I see where the totals come from--Galveston, New Orleans, Cameron. Should I worry about the Big One or the Next One? The worst case or the most likely case? My answer is the worst case.We dodged catastrophe with Ike. If the storm had not turned at the last hour, Galveston would have had the worst. It was so close. Very close.Unfortunately you and I both know Galveston is very susceptible to hurricanes, (even with the sea wall they built in the early 1900,s ) and someday the inevitable will happen. However, the coastal residents of Texas are up to snuff when it comes to hurricane watches and warnings.
391. bappit
 379"Because storm surge-induced flooding has killed more people in the United States in hurricanes than all other hurricane-related threats (freshwater flooding, winds, and tornadoes) combined since 1900 the National Oceanic and Atmospheric Administration is working to enhance the analysis and prediction of storm surge."Seems not too long ago people were saying that freshwater flooding killed the most people. I think I see where the totals come from--Galveston, New Orleans, Cameron. Should I worry about the Big One or the Next One? The worst case or the most likely case? My answer is the worst case.We dodged catastrophe with Ike. If the storm had not turned at the last hour, Galveston would have had the worst. It was so close.
 Tropical Cyclone Warning Center PerthTropical Cyclone AdvisoryTROPICAL CYCLONE ROBYN, CAT 1 (12U)9:00 AM WST April 6 2010=================================At 0:00 AM UTC, Tropical Cyclone Robyn, Category 1 (992 hPa) located at 16.0S 92.1E has 10 minute sustained winds of 40 knots with gusts of 55 knots. The cyclone is reported as moving northwest at 1 knots.Gale-Force Winds==================60 NM from the center in northern quadrant120 NM from the center in southeast quadrant90 NM from the center in southwest quadrantDvorak Intensity: T2.5/3.0/W2.0/24HRSForecast and Intensity===========================12 HRS: 16.0S 91.2E - 35 knots (CAT 1)24 HRS: 16.2S 89.9E - 35 knots (CAT 1)48 HRS: 16.7S 86.7E - 30 knots (Tropical Low)72 HRS: 17.1S 82.2E - 30 knots (Tropical Low)Additional Information=========================Tropical Cyclone Robyn is weakening under increasing northwesterly wind shear [now more than 20 knots]. Deep convection is now displaced more than a degree southeast of the LLCC. Dvorak analysis: DT=2.0 [shear pattern LLCC >3/4 degree from temperature gradient], FT contrained to 2.5 and CI held at 3.0. Robyn has moved slowly in the last 18 hours as higher level northwesterly steering flow competes with lower level westerly flow. As Robyn continues to shear, the westerly steering should dominate associated with a strengthening ridge to the southwest in the wake of an amplifying mid-level trough off the Western Australian coast. While Robyn is likely to weaken below cyclone intensity in the next 12 hours or so, gale-force winds should persist on the southern side assisted by translation and the strong ridge to the south.
389. hydrus
 Quoting presslord:I believe early May will provide more answers as to what kind of numbers and possible tracks might occur.Action: Quote | Ignore User this sort of responsible approach will NOT be tolerated... lol.i get no respect i tell ya, no respect. :) One of my favorite Dangerfield quotes.
388. presslord
 I believe early May will provide more answers as to what kind of numbers and possible tracks might occur.Action: Quote | Ignore User this sort of responsible approach will NOT be tolerated...
Member Since: August 13, 2007 Posts: 0 Comments: 10538
387. GeoffreyWPB
 Quoting hydrus:I do not think we will have anything close to what happened in 2005 for a very long time. It is early yet and a lot can change in the tropics in a short amount of time. As far as analog years, I believe early May will provide more answers as to what kind of numbers and possible tracks might occur.We are very much in agreement Hydrus.
385. atmoaggie
 Quoting StormW:atmo, can I access that?Ummm, the code is free for gov and edu. Data, well, we are working on that.This is not something that runs on a single machine well, like SLOSH.2 hour run time of a grid of acceptable resolution 5 days out takes a cluster with a minimum of 512 processor cores (more if older than a year ago), infiniband, etc.An atlas will eventually be available...but to whom and in what form, I cannot say. For different projects and missions, USACE, FEMA, universities, and a few others have run thousands of real and hypothetical storms. Just needs to be put together somewhere with a display system...but the trick is for everyone to be in a sharing mood.Quoting BahaHurican:316. atmoaggieDEFinitely see where u are coming from. It seems to me maybe some technology upgrades are in order? :o) Even something as simple as an improved weather monitoring system where the anometer lasts past 120 mph winds? Where the station doesn't shut down when the power goes off? And that' not even talking about computer programming and hardware... lol.NOS sentinel program was intended to be something like that...need a bunch more coverage, IMO, though.
383. hydrus
 Quoting GeoffreyWPB:It seems there is no comparison to the SST's from 2005 against the current SST temps. Also, from maps that were posted earlier, the 2005 El Nino was pretty much gone as opposed to what remains of it today. As of this posting, I do not see '05 as an analog year. I do not think we will have anything close to what happened in 2005 for a very long time. It is early yet and a lot can change in the tropics in a short amount of time. As far as analog years, I believe early May will provide more answers as to what kind of numbers and possible tracks might occur.
382. GeoffreyWPB
 It seems there is no comparison to the SST's from 2005 against the current SST temps. Also, from maps that were posted earlier, the 2005 El Nino was pretty much gone as opposed to what remains of it today. As of this posting, I do not see '05 as an analog year.
381. Patrap
Member Since: July 3, 2005 Posts: 438 Comments: 136330
380. Tropicsweatherpr
 The 30 day SOI index continues to go up rapidly.
379. Patrap
 The Saffir-Simpson Hurricane Wind Scale was updated in early 2010. Below are links to the updated documents which were accepted by the National Weather Service. Storm Surge Scales and Storm Surge ForecastingView document in PDF formatDuring the open public comment period for the draft of the Saffir-Simpson Hurricane Wind Scale, many people suggested that the National Weather Service develop a storm surge specific scale as well as improve its forecasting of storm surge. It is acknowledged that there are some researchers who advocate developing another scale for hurricanes specifically geared toward storm surge impact1,2 by incorporating aspects of the system's size. However, the National Hurricane Center does not believe that such scales would be helpful or effective at conveying the storm surge threat. For example, if 2008's Hurricane Ike had made landfall in Palm Beach, Florida, the resulting storm surge would have been only 8', rather than the 20' that occurred where Ike actually made landfall on the upper Texas coast. These greatly differing surge impacts arise from differences in the local bathymetry (the shallow Gulf waters off of Texas enhance storm surge while the deep ocean depths off of southeastern Florida inhibit surge). The proposed storm surge scales that consider storm size do not consider these local factors that play a crucial role in determining actual surge impacts.The National Weather Service believes that a better approach is to focus directly on conveying the depth of inundation expected at the coast and inland. Because storm surge-induced flooding has killed more people in the United States in hurricanes than all other hurricane-related threats (freshwater flooding, winds, and tornadoes) combined since 1900 the National Oceanic and Atmospheric Administration is working to enhance the analysis and prediction of storm surge. Direct estimates of inundation are being communicated in the NHC's Public Advisories and in the Weather Forecast Office's Hurricane Local Statements. New ways of communicating the threat have also been developed. NHC's probabilistic storm surge product, which provides the likelihood of storm surge values from 2 through 25 feet, became operational in 2009, and the NWS's Meteorological Development Laboratory is providing experimental, probabilistic storm surge exceedance products for 2010. In addition, coastal WFOs will provide experimental Tropical Cyclone Impacts Graphics in 2010; these include a qualitative graphic on the expected storm surge impacts. Finally, the NWS is exploring the possibility of issuing explicit Storm Surge Warnings, and such warnings could be implemented in the next couple of years. In all of these efforts, the NWS is working to provide specific and quantitative information to support decision-making at the local level.
Member Since: July 3, 2005 Posts: 438 Comments: 136330
378. BDAwx
 scale of 1-4 for wind, surge, and flooding potential 1 nuisance - minor damage2 minor damage - moderate damage3 moderate damage - major damage4 >/=major damagetake an average. then describe where that number came from in the advisory/warning. eg.category 1 storm Winds that will generally be a nuisance but with isolated pockets of minor damage, a storm surge that will cover the beaches and be little more than an erosion event, and 1 inch of rain in a 6 hour period that will cause ponding on some roadways and flood some low lying areas that typically flood during heavy rain events.most of the general public doesn't know what 175mph wind will do to their house, or if a 20foot storm surge would reach them, or what 10 inches of rain will do to them. so its useless to say that there is a storm with 175mph winds approaching them that will cause a 20 foot storm surge and potentially 10 inches of rain. You have to explain that 175mph winds will just about level most structures, and a 20 foot storm surge will essentially raise the sealevel so that it will be at so and so's front door step and there will be deadly surf on top of that. Then, that even if your home managed to survive both the cat5 winds and the 20ft storm surge that it could be washed away by major river flooding caused by the 10inches of rain. But I do think that whatever is done needs to be understood by and delivered accurately to the public or it is just a waste. Also, if the forecasts of "doom" don't pan out I agree that an explanation of why this happened is necessary to avoid complacency. A work in progress, certainly. We could always do like we do with tornadoes and send out a watch, then a warning, then go survey the damage to estimate a category. :) jk.
377. Patrap
 SST GOM 4 April 20094 April 2010
Member Since: July 3, 2005 Posts: 438 Comments: 136330
376. Patrap
 Tropical Cyclone Heat PotentialGulf of Mexico FieldsDate: Apr 4 2010Tropical Cyclone Heat Potential LoopSea Height Anomaly4 April 2009
Member Since: July 3, 2005 Posts: 438 Comments: 136330
375. msgambler
 You probably know more than me. I live on the GOM. If I have an earthquake I'm running for the hills. Just trying to recall discussions from weeks past about the subject and want to say I remember hearing someone mention that
373. KEEPEROFTHEGATE (Mod)
 Quoting msgambler:KOTG, possible these are pershocks instead of the main event? What is your take. Been talking months about moving up towards SAF. Could be a release there.maybe if it follows the pattern next big shaker just ne of la sw offshore of san fran but hey what do i know just the pattern is sa/cen america/west coast then cen america now s america next will be back to west coast or cen america up near wash/bc been quiet maybe some type of release there too soon
Member Since: July 15, 2006 Posts: 193 Comments: 60433
371. Bordonaro
 MESOSCALE DISCUSSION 0258 NWS STORM PREDICTION CENTER NORMAN OK 0610 PM CDT MON APR 05 2010 AREAS AFFECTED...WRN OK...S-CNTRL KS CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 052310Z - 060045Z A CONDITIONAL SEVERE THREAT WILL EXIST ALONG RETREATING DRYLINE ACROSS WRN OK...WITH ISOLATED TSTM DEVELOPMENT POSSIBLE BUT UNLIKELY THROUGH ABOUT 03Z. A WW COULD BECOME NECESSARY IF TSTM INITIATION DOES INDEED OCCUR. 23Z SUBJECTIVE SURFACE ANALYSIS PLACED A CYCLONE NEAR BIE WITH A RETREATING DRYLINE DRAPED S/SWWD FROM AROUND MHK TO GAG TO MAF. CONVERGENCE ALONG THE BOUNDARY APPEARS RATHER MODEST...BUT SOME INCREASE IN CU FIELD HAS BEEN NOTED ACROSS W-CNTRL OK. THE LACK OF APPRECIABLE MID-LEVEL HEIGHT FALLS AND MODEST LOW-LEVEL CONVERGENCE SHOULD MITIGATE TSTM DEVELOPMENT DESPITE DECREASING MLCIN. LATEST OPERATIONAL AND HI-RES GUIDANCE SUPPORT THIS SCENARIO WITH MINIMAL TO NO INITIATION SIGNAL THIS EVENING. NEVERTHELESS...SOME INCREASE IN LARGE-SCALE ASCENT MAY OCCUR ON THE TAIL-END OF APPARENT IMPULSE AND ASSOCIATED CI FIELD SHIFTING EWD FROM THE CNTRL HIGH PLAINS. IF TSTM DEVELOPMENT DOES OCCUR...ALL MODES OF SEVERE WEATHER APPEAR POSSIBLE GIVEN A VERY UNSTABLE/STRONGLY SHEARED ENVIRONMENT. ..GRAMS.. 04/05/2010
Member Since: August 25, 2009 Posts: 20 Comments: 6785
370. Bordonaro
 Quoting msgambler:KOTG, possible these are pershocks instead of the main event? What is your take. Been talking months about moving up towards SAF. Could be a release there.Plate tectonics is not an exact science. Only God knows for sure which plate system will create the next earthquake. From a historical perspective, both N and S CA are "overdue" for the "next Big One", 7.0Mw or greater on the Richter Scale!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
 Quoting msgambler:re 365: her and hubby graduate next month (I think)oh ok thats great
Member Since: June 28, 2006 Posts: 25 Comments: 8516
367. msgambler
 re 365: her and hubby graduate next month (I think)
366. msgambler
 KOTG, possible these are pershocks instead of the main event? What is your take. Been talking months about moving up towards SAF. Could be a release there.
 Quoting msgambler:Just keep those storms away from Lafayette, IN. I have a niece at Perduethat's where I go
Member Since: June 28, 2006 Posts: 25 Comments: 8516
364. msgambler
 re 362: thank goodness cause as usual I can't get her to answer her phone.
363. KEEPEROFTHEGATE (Mod)
 the next shock on west coast or off nic.e pac
Member Since: July 15, 2006 Posts: 193 Comments: 60433
362. Bordonaro
 Quoting msgambler:Just keep those storms away from Lafayette, IN. I have a niece at PerdueAll is quiet in N Central IN!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
361. Bordonaro
 #358, thankfully this is pretty much a non-event
Member Since: August 25, 2009 Posts: 20 Comments: 6785
360. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 193 Comments: 60433
 .
358. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 193 Comments: 60433
357. msgambler
 Just keep those storms away from Lafayette, IN. I have a niece at Perdue
356. Bordonaro
 MESOSCALE DISCUSSION 0257 NWS STORM PREDICTION CENTER NORMAN OK 0547 PM CDT MON APR 05 2010 AREAS AFFECTED...IL...IND...NRN KY...SWRN OH CONCERNING...TORNADO WATCH 49...50... VALID 052247Z - 052345Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 49...50...CONTINUES. ...SEVERE THREAT HAS SPREAD A BIT EAST OF WW50. COUNTIES MAY NEED TO BE ADDED TO ACCOUNT FOR THIS DEVELOPMENT... LATEST WV IMAGERY SUGGESTS SHORTWAVE RIDGING IS OVERSPREADING MUCH OF ERN MO/SRN IL. RADAR DATA SUPPORTS THIS PER RAPID DEMISE OF SUPERCELL OVER MONTGOMERY/SHELBY COUNTY IN CNTRL IL. OTHER MORE NUMEROUS SEVERE THUNDERSTORMS HAVE CLUSTERED ALONG AN AXIS FROM ECNTRL IL...SEWD ACROSS CNTRL IND INTO NRN KY. THIS ACTIVITY APPEARS TO BE STRONGLY TIED TO RETREATING WARM FRONT AND SUSTAINED LOW LEVEL WARM ADVECTION IS LIKELY TO AID THESE UPDRAFTS FOR THE NEXT SEVERAL HOURS. GIVEN THAT DEEP LAYER AND FAVORABLE LOW LEVEL SHEAR WILL REMAIN SUPPORTIVE OF SUPERCELL ACTIVITY THERE REMAINS A DISTINCT POSSIBILITY FOR ISOLATED TORNADOES. WEAK SUBSIDENCE SHOULD GRADUALLY OVERSPREAD THE REMAINDER OF WW49 FORCING THE BULK OF STRONGER UPDRAFTS INTO THE OH VALLEY. ..DARROW.. 04/05/2010
Member Since: August 25, 2009 Posts: 20 Comments: 6785
355. Patrap
Member Since: July 3, 2005 Posts: 438 Comments: 136330

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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