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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355. Patrap
Member Since: July 3, 2005 Posts: 438 Comments: 136276
354. drg0dOwnCountry
 MARCH 2010 UAH Global Temperature Update: +0.65 deg. CThe global-average lower tropospheric temperature continues to be quite warm: +0.65 deg. C for March, 2010. This is about the same as January. Global average sea surface temperatures (not shown) remain high.As a reminder, last month we change to Version 5.3 of our dataset, which accounts for the mismatch between the average seasonal cycle produced by the older MSU and the newer AMSU instruments. This affects the value of the individual monthly departures, but does not affect the year to year variations, and thus the overall trend remains the same as in Version 5.2.ALSO…we have now added the NOAA-18 AMSU, which provides data since June of 2005. The local observation time of NOAA-18 (now close to 2 p.m., ascending node) is similar to that of NASA’s Aqua satellite (about 1:30 p.m.). The temperature anomalies listed above have changed somewhat as a result of adding NOAA-18.[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT's are individually calibrated in a laboratory before being installed in the instruments.]
353. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 193 Comments: 60407
350. Bordonaro
 4 Counties under Tornado Warning, what a mean group of storms:
349. Bordonaro
 MESOSCALE DISCUSSION 0256 NWS STORM PREDICTION CENTER NORMAN OK 0523 PM CDT MON APR 05 2010 AREAS AFFECTED...ERN IA...NRN IL CONCERNING...SEVERE THUNDERSTORM WATCH 48... VALID 052223Z - 052330Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 48 CONTINUES. SEVERE HAIL THREAT WITH ELEVATED TSTMS WILL PERSIST OVER NERN PORTIONS OF WW 48 IN CNTRL/ERN IA...AND SHOULD EXTEND EWD WITHIN A RELATIVELY NARROW CORRIDOR INTO NRN IL. WFO AREAL EXTENSION OR AN ADDITIONAL SEVERE TSTM WATCH COULD BECOME NECESSARY ACROSS FAR ERN IA INTO NRN IL. AS OF 2215Z...SCATTERED STRONG TO SEVERE TSTMS WITH A HISTORY OF PRODUCING HAIL WERE LOCATED FROM IOWA TO GRUNDY COUNTIES IN IA. THIS ACTIVITY REMAINS ROOTED ABOVE A STABLE NEAR-SURFACE LAYER...N OF WARM FRONT LYING ALONG THE IA/MO BORDER INTO CNTRL IL. LATEST MODEL FORECASTS SUPPORT ROBUST LOW-LEVEL WARM THETA-E ADVECTION CONTINUING AND SHIFTING EWD THROUGH THE EARLY EVENING. THIS SHOULD MAINTAIN FAVORABLE LIFT AND PROMOTE DOWNSTREAM DESTABILIZATION WITH WEAK ELEVATED INSTABILITY FOR TSTMS TO PERSIST EWD INTO NRN IL. GIVEN 500 MB FLOW AROUND 60 KT /PER SLATER IA PROFILER/...STRONG EFFECTIVE SHEAR SHOULD MAINTAIN POTENTIAL FOR SEVERE HAIL.
348. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 193 Comments: 60407
347. Bordonaro
 Quoting tornadodude:I cant go today, got too much to do :pProbably for the best. Those T- Storms are REAL NASTY. Golf-ball/baseball sized hail and 60 MPH winds, maybe a surprise tornado or two.See, your Tornado Warning!!
 Tornado WarningTORNADO WARNINGINC021-119-133-052245-/O.NEW.KIND.TO.W.0003.100405T2219Z-100405T2245Z/BULLETIN - EAS ACTIVATION REQUESTEDTORNADO WARNINGNATIONAL WEATHER SERVICE INDIANAPOLIS IN619 PM EDT MON APR 5 2010THE NATIONAL WEATHER SERVICE IN INDIANAPOLIS HAS ISSUED A* TORNADO WARNING FOR... EAST CENTRAL CLAY COUNTY IN WEST CENTRAL INDIANA... NORTHERN OWEN COUNTY IN WEST CENTRAL INDIANA... SOUTHERN PUTNAM COUNTY IN WEST CENTRAL INDIANA...* UNTIL 645 PM EDT* AT 617 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED 11 MILES SOUTHEAST OF BRAZIL...OR 21 MILES EAST OF TERRE HAUTE...AND MOVING EAST AT 35 MPH.* THIS TORNADIC STORM WILL BE NEAR... CAGLES MILL LAKE AROUND 630 PM EDT... DEVORE AROUND 640 PM EDT...THIS INCLUDES INTERSTATE 70 BETWEEN MILE MARKERS 24 AND 28.PRECAUTIONARY/PREPAREDNESS ACTIONS...TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF ASTURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OROUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECTYOURSELF FROM FLYING DEBRIS.&&LAT...LON 3951 8674 3929 8672 3932 8709 3946 8712TIME...MOT...LOC 2219Z 266DEG 30KT 3940 8697\$\$JH
Member Since: June 28, 2006 Posts: 25 Comments: 8516
 Quoting Bordonaro:Cool, just be careful! Get some good pictures/videos for us to see!!I cant go today, got too much to do :p
Member Since: June 28, 2006 Posts: 25 Comments: 8516
344. Bordonaro
 Quoting TampaSpin:S Ca and N Mexico have been moving quite a bit the last day or so!! Most aftershocks have been in the 3-4 Mw range today.
342. Bordonaro
 Quoting tornadodude:part of the risk of storm chasing tho ;)Cool, just be careful! Get some good pictures/videos for us to see!!
 Quoting Bordonaro:Unless you want a hail damaged vehicle or to be blown/swept off the road by high winds/torrential rain, I'd stay put. Those storms are serious!!part of the risk of storm chasing tho ;)
Member Since: June 28, 2006 Posts: 25 Comments: 8516
340. Bordonaro
 Quoting tornadodude:it is really impressive looking, I could drive to it, but I dont know if I would be too lateUnless you want a hail damaged vehicle or to be blown/swept off the road by high winds/torrential rain, I'd stay put. Those storms are serious!! Notice the rotating cells? These storms are like the T-Storms we get here in TX.
339. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 193 Comments: 60407
338. atmoaggie
 Quoting SouthDadeFish:Atmo, how much longer do you think till we get computers that can process ADCIRC in reasonable time? i.e. one that will allow it to be put into real time advisories or shortly thereafter?We can do it now with the advisory and one or two other possibilities right now if all goes right. But not on our most competent grids that include all of the needed details.How long until we can do a realtime run in a decent time frame (which I'll call 30 minutes, for now)? Soon, but probably not soon for an ensemble that includes a speedup, slowdown, stronger, weaker, left 30 miles, right 30 miles, etc. We are not ready to just run one surge model and be done with it, too much variability in track, speed, and intensity of hurricanes...(and we aren't perfect at those 4 days out when it high time to be leaving town.)(The new DDR3 processor-memory threads are helping!)Example of the computation: We have run ADCIRC grids that have computational points as close as 8 meters apart...compare to weather models that run at 3 km (and those are the high resolution ones). The geeks in here will recognize that this means you must lower the timestep, the time elapsed in between physical calculations...ADCIRC runs anywhere from 0.5 to 2.0 seconds timestep. WRF from 24 seconds to 4 minutes.
 Quoting Unfriendly:id say O3 on wunderground radar has a good amount of rotation - id keep an eye on this one, traveling right down I-70.it is really impressive looking, I could drive to it, but I dont know if I would be too late
Member Since: June 28, 2006 Posts: 25 Comments: 8516
336. KEEPEROFTHEGATE (Mod)
 Quoting GeoffreyWPB:BREAKING NEWS: Roof Collapse in Raleigh County Mine, Six Miners Killed god show mercy for there souls
Member Since: July 15, 2006 Posts: 193 Comments: 60407
335. hydrus
 Quoting RitaEvac:Going from the freezer to the burner in the South. Temp wise. Yeah, I know. And here I was looking forward to low 70,s during the day, 50,s at night, and no A/C electric bill. once again Mother Nature holds the cards.:)
334. KEEPEROFTHEGATE (Mod)
 Quoting tornadodude:some returns in the 70 dbz range with the cell south east of Terre Hautelink
Member Since: July 15, 2006 Posts: 193 Comments: 60407
333. GeoffreyWPB
 oh nevermind. I guess pre-run will work too.
Member Since: August 12, 2007 Posts: 11 Comments: 2449
331. RitaEvac
 2 months we could be watching a storm
330. Unfriendly
 id say O3 on wunderground radar has a good amount of rotation - id keep an eye on this one, traveling right down I-70.
329. 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.
328. RitaEvac
 Dead of winter, to dead of summer. Skip spring and straight into cane season with high octane fuel waters
 some returns in the 70 dbz range with the cell south east of Terre Hautelink
Member Since: June 28, 2006 Posts: 25 Comments: 8516
326. KEEPEROFTHEGATE (Mod)
 days work done waitin on the wife and dinner a record breaker as for temps here my loc recorded a high of 76.5 at 1600 now 74 at 1800 T Storms by mid morning rolling in with rain after that till late wed temp start a slow drop after storms tomorrow afternoon and evening then near normal by sat
Member Since: July 15, 2006 Posts: 193 Comments: 60407
325. atmoaggie
 Quoting StormW:What would it work out to with the range of the plus or minus 20%???? The problem is that SLOSH doesn't represent small (laterally), but very important land surface features well. Port Arthur has a seawall, too, but it wasn't involved in that plot, nor any other, for a while (In fact, I have been told that if you call Port Arthur and ask about the elevation of the seawall 6 times, you'll get 6 different answers).We need a better tool for surge forecasts that relies on an ensemble of tracks and intensities whose surge results are in an atlas. Pre-run, not operationally, using ADCIRC. Nothing else will come close.And, of course, it needs to have good elevation data in it of every road bed, railroad, levees, weirs, culverts, etc. All of the things that make ADCIRC powerful are on the scale of only a few meters.And we are getting there. This is coming...
324. RitaEvac
 Going from the freezer to the burner in the South. Temp wise.
 Atmo, how much longer do you think till we get computers that can process ADCIRC in reasonable time? i.e. one that will allow it to be put into real time advisories or shortly thereafter?
Member Since: August 12, 2007 Posts: 11 Comments: 2449
322. KEEPEROFTHEGATE (Mod)
 Quoting Patrap:Up to \$3.50 lb now for select Bell River Crawdads.Way too High.there gonna be pricy for a while maybe even higher may be next spring before they will be abundant again cold winter kill em off and any that are left are small
Member Since: July 15, 2006 Posts: 193 Comments: 60407
320. atmoaggie
 Quoting Patrap:I gotta go find some Lower priced crawdads..For sanity's sake.You find big ones for less than \$3.50 a pound, please tell me where. (Live, that is.)
319. hydrus
 Quoting Patrap:Emg Mgt isnt a Job..its a adventure. And it can be a tragic adventure too. I do say a prayer for those folks when disaster strikes.
318. Patrap
 Up to \$3.50 lb now for select Bell River Crawdads.Way too High.
Member Since: July 3, 2005 Posts: 438 Comments: 136276
317. jeffs713
 Quoting Patrap:Seems the Rita folks skee-daddled mighty fast ol atmo..LOLSo, the premise may sound good,its far from the truth or Human nature.I gotta go find some Lower priced crawdads..Lurking has been fun.And enlightening as well.Im on a 4-6 post Limit till June 1.Self imposed.For sanity's sake.What are the prices like over there? The other half and I picked some up a week and a half ago for \$2.75/lb.
316. atmoaggie
 Quoting BahaHurican: So basically what u are saying is even the wx scientists don't "know" what's happening with storm surge... I keep thinking about Katrina's storm surge in MS, which nobody expected to go so high because it wasn't cat 5 anymore...Well, they should have...We are making some strides in surge forecasts...or, actually atlases of hypothetical storms.We are not really able to run a good, dynamical surge forecast for a half-dozen possible scenarios, currently. SLOSH is a little idealized and doesn't include a lot of info (like sea walls, levees, road beds, etc). ADCIRC is the way to do that.BUT, ADCIRC is too involved to run an ensemble in forecast mode, for the most part. Few computers on the planet can do that. It is far more intense than a weather model.For example, in my office we can run a north america WRF run in under 30 minutes (depending on...well, a lot of things). A competent ADCIRC run takes closer to 100 hours...about the length of time simulated, on the same cluster.
315. Patrap
 Seems the Rita folks skee-daddled mighty fast ol atmo..LOLSo, the premise may sound good,its far from the truth or Human nature. I gotta go find some Lower priced crawdads..Lurking has been fun.And enlightening as well.Next PostThe next post will probably be Wednesday, and will be a guest post, since I am on vacation this week (I'm going to go experience the weather underground in Mammoth Cave!)Jeff MastersHmmm.........,I wunder who the Guest Entry will be authored by?Stay Tuned
Member Since: July 3, 2005 Posts: 438 Comments: 136276
314. NRAamy
 311. Patrap 2:42 PM PDT on April 05, 2010 Amazing disinformation can and will be slung like Banta Fodder here sometimes.. that needs to be posted at the top of this blog!!!!!!!!!!;)
313. atmoaggie
 Quoting Patrap:Georges had Null effect on NOLA in 98,Dennis in 05,and Ivan in 04 spurned evacs here and had some effect on the Katrina evac,as well as Cat 1 Cindy which made a direct strike in July 05.But no one nationally could even spell Levee for those Storms...but one has to quantify Public safety and err on the side of caution...Always.Thats why Emg Mgrs are NEVER Mets..Yeeeeeaaaahhhhh.Doesn't matter if they are postal carriers. Forecast doom. It doesn't happen. No one listens the next time.
312. BahaHurican
 While we've made some significant improvements in forecasting track over the last few years, there's obviously a lot more to be done. IMO, the improvement of SLOSH-type forecasters are vital to reducing the costs of hurricane impacts over the next 20 years.
311. Patrap
 Amazing disinformation can and will be slung like Banta Fodder here sometimes..Hurricane KATRINA Advisory ArchiveHurricane KATRINAZCZC MIATCPAT2 ALLTTAA00 KNHC DDHHMMBULLETINHURRICANE KATRINA SPECIAL ADVISORY NUMBER 20NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL1 AM CDT SUN AUG 28 2005 ...KATRINA STRENGTHENS TO CATEGORY FOUR WITH 145 MPH WINDS...A HURRICANE WARNING IS IN EFFECT FOR THE NORTH CENTRAL GULF COASTFROM MORGAN CITY LOUISIANA EASTWARD TO THE ALABAMA/FLORIDABORDER...INCLUDING THE CITY OF NEW ORLEANS AND LAKE PONTCHARTRAIN.A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTEDWITHIN THE WARNING AREA WITHIN THE NEXT 24 HOURS. PREPARATIONS TOPROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION. A TROPICAL STORM WARNING AND A HURRICANE WATCH ARE IN EFFECT FROMEAST OF THE ALABAMA/FLORIDA BORDER TO DESTIN FLORIDA...AND FROMWEST OF MORGAN CITY TO INTRACOASTAL CITY LOUISIANA. A TROPICALSTORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTEDWITHIN THE WARNING AREA WITHIN THE NEXT 24 HOURS. A HURRICANE WATCHMEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN THE WATCHAREA...GENERALLY WITHIN 36 HOURS. FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLEINLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUEDBY YOUR LOCAL WEATHER OFFICE. AT 1 AM CDT...0600Z...THE CENTER OF HURRICANE KATRINA WAS LOCATEDNEAR LATITUDE 25.1 NORTH... LONGITUDE 86.8 WEST OR ABOUT 310MILES... 500 KM... SOUTH-SOUTHEAST OF THE MOUTH OF THE MISSISSIPPIRIVER. KATRINA IS MOVING TOWARD THE WEST-NORTHWEST NEAR 8 MPH. A GRADUALTURN TOWARD THE NORTHWEST IS EXPECTED LATER TODAY. REPORTS FROM AN AIR FORCE RECONNAISSANCE AIRCRAFT INDICATE THATMAXIMUM SUSTAINED WINDS HAVE INCREASED AND ARE NOW NEAR 145MPH...WITH HIGHER GUSTS. KATRINA IS A CATEGORY FOUR HURRICANE ONTHE SAFFIR-SIMPSON SCALE. SOME ADDITIONAL STRENGTHENING IS POSSIBLETODAY. HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110 KM...FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UPTO 160 MILES...260 KM. THE MINIMUM CENTRAL PRESSURE RECENTLY REPORTED BY THE RECONNAISSANCEAIRCRAFT WAS 935 MB...27.61 INCHES.COASTAL STORM SURGE FLOODING OF 15 TO 20 FEET ABOVE NORMAL TIDELEVELS...LOCALLY AS HIGH AS 25 FEET ALONG WITH LARGE AND DANGEROUSBATTERING WAVES...CAN BE EXPECTED NEAR AND TO THE EAST OF WHERE THECENTER MAKES LANDFALL. HEAVY RAINS FROM KATRINA SHOULD BEGIN TO AFFECT THE CENTRAL GULFCOAST SUNDAY EVENING. RAINFALL TOTALS OF 5 TO 10 INCHES...WITHISOLATED MAXIMUM AMOUNTS OF 15 INCHES...ARE POSSIBLE ALONG THE PATHOF KATRINA. THE HURRICANE IS STILL EXPECTED TO PRODUCE ADDITIONALRAINFALL AMOUNTS OF 2 TO 4 INCHES OVER EXTREME WESTERN CUBA...AND 1TO 3 INCHES OF RAINFALL IS EXPECTED OVER THE YUCATAN PENINSULA. REPEATING THE 1 AM CDT POSITION...25.1 N... 86.8 W. MOVEMENTTOWARD...WEST-NORTHWEST NEAR 8 MPH. MAXIMUM SUSTAINEDWINDS...145 MPH. MINIMUM CENTRAL PRESSURE... 935 MB. THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT4 AM CDT. FORECASTER KNABB \$\$NNNN
Member Since: July 3, 2005 Posts: 438 Comments: 136276
310. BahaHurican
 Quoting atmoaggie:That early surge was a Gulf shelf-traveling Kelvin wave that brought up water levels ahead of the actual surge. Not expected by anyone, but could have been by following the water level changes starting at Mobile and traveling west.Is only now beginning to be reproduced by surge models 18 months later...that being the early wave independent of the classic wind-driven surge. So basically what u are saying is even the wx scientists don't "know" what's happening with storm surge... I keep thinking about Katrina's storm surge in MS, which nobody expected to go so high because it wasn't cat 5 anymore...
309. atmoaggie
 Quoting BahaHurican: If we are talking about Ike in particular, I keep thinking that the storm surge forecasts were not that far off, and that they were pretty extensively broadcast. If we are talking Katrina, that is a different story all together.I think some of the others were corect in saying that many pple in the general public don't have a complete understanding of what a "storm surge of 15 feet" really entails. Hey, even as a "hurricane-savvy" person, I don't KNOW what it's like. Something I remember from Ike is pple who lived on Bolivar Peninsula getting stuck there because the storm surge started to come in sooner than they expected. Some actually helped others evacuate! Though they were long-time GOM dwellers, their limited understanding of the mechanics of the storm surge limited their ability to make wise decisions.That early surge was a Gulf shelf-traveling Kelvin wave that brought up water levels ahead of the actual surge. Not expected by anyone, but could have been by following the water level changes starting at Mobile and traveling west.Is only now beginning to be reproduced by surge models 18 months later...that being the early wave independent of the classic wind-driven surge.
308. BahaHurican
 Quoting Eagle101:Storm,Funny you should mention this. I have been experimenting with a vortex simulator (VERY small scale) and noticed this anomaly. I would see a pressure drop (via instrumentation), but there would be, on average, a five to six second delay in formation. I am no expert in atmospheric dynamics, just some rudimentary knowledge of incompressible aerodynamics. I found it interesting that, after the delay, there would be a rather rapid spin-up (less than one second.) Without boring anyone, is there a body of work I could use to better educate myself? Thanks Storm.Very Respectfully,Jon This sounds pretty interesting.
 Quoting Jeff9641:I think Butler wins tonight. Butler seems to be very talented and Duke may get caught off gaurd.hope so ;)
Member Since: June 28, 2006 Posts: 25 Comments: 8516
306. Patrap
 Quoting atmoaggie:Except that if you forecast doom that doesn't transpire, no one listens in the future.All of the forecasts and most of the hindcasts put surge up to Beaumont, bury Port Arthur and Orange, flood Lake Charles. Yes, parts of Orange had some water, but most of the structures in the Golden Triangle, outside of Bridge City, of course, were spared.One that does all that is the SLOSH in your link: http://img391.imageshack.us/img391/1640/galvcat3hightidedisplayba6.pngGot Bolivar, Ship Channel and San Jacinto right, overkill in lots of other places.NOLA was evacuated very much like that for Katrina but in 1998 for Georges. He was almost a Betsy. But levees held, houses were fine, the Superdome was a last-resort shelter (and, thus, looted, of course), but I wonder how many stayed for Katrina after evacuating for Georges only to come back to no doom whatsoever. Then not realizing how close to doom they really were.Big perception issue with the general public. If you forecast doom, you better be right on, or expect some portion of everyone to have doubts about anything you or anyone else in the business has to say next time doom is the forecast, right or wrong. If wrong, they need to know why, how it will be improved based on what was learned, and how close it really was.Georges had Null effect on NOLA in 98,Dennis in 05,and Ivan in 04 spurned evacs here and had some effect on the Katrina evac,as well as Cat 1 Cindy which made a direct strike in July 05.But no one nationally could even spell Levee for those Storms...but one has to quantify Public safety and err on the side of caution...Always.Thats why Emg Mgrs are NEVER Mets..
Member Since: July 3, 2005 Posts: 438 Comments: 136276
 Severe Thunderstorm WarningSEVERE THUNDERSTORM WARNINGINC063-097-052215-/O.NEW.KIND.SV.W.0003.100405T2130Z-100405T2215Z/BULLETIN - IMMEDIATE BROADCAST REQUESTEDSEVERE THUNDERSTORM WARNINGNATIONAL WEATHER SERVICE INDIANAPOLIS IN530 PM EDT MON APR 5 2010THE NATIONAL WEATHER SERVICE IN INDIANAPOLIS HAS ISSUED A* SEVERE THUNDERSTORM WARNING FOR... SOUTHEASTERN HENDRICKS COUNTY IN CENTRAL INDIANA... MARION COUNTY IN CENTRAL INDIANA...* UNTIL 615 PM EDT* AT 529 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR PLAINFIELD...OR 13 MILES WEST OF INDIANAPOLIS...AND MOVING EAST AT 30 MPH.* THE SEVERE THUNDERSTORM WILL BE NEAR... CAMBY AROUND 535 PM EDT... INDIANAPOLIS INT`L AIRPORT...CLERMONT AND EAGLE CREEK RESERVOIR AROUND 540 PM EDT... SPEEDWAY AROUND 545 PM EDT... SPRING HILL AND WYNNEDALE AROUND 550 PM EDT... MONUMENT CIRCLE...INDIANAPOLIS...HOMECROFT AND ROCKY RIPPLE AROUND 555 PM EDT... BEECH GROVE...INDIANA STATE FAIRGROUNDS...SOUTHPORT AND BROAD RIPPLE AROUND 600 PM EDT...THIS INCLUDES INTERSTATE 65 BETWEEN MILE MARKERS 101 AND 122.THIS INCLUDES INTERSTATE 70 BETWEEN MILE MARKERS 63 AND 93.THIS INCLUDES INTERSTATE 74 BETWEEN MILE MARKERS 68 AND 99.PRECAUTIONARY/PREPAREDNESS ACTIONS...SEVERE THUNDERSTORMS PRODUCE DAMAGING WIND IN EXCESS OF 60 MILES PERHOUR...DESTRUCTIVE HAIL...DEADLY LIGHTNING...AND VERY HEAVY RAIN. FORYOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF YOURHOME OR BUSINESS. HEAVY RAINS FLOOD ROADS QUICKLY SO DO NOT DRIVEINTO AREAS WHERE WATER COVERS THE ROAD.&&A TORNADO WATCH REMAINS IN EFFECT UNTIL MIDNIGHT EDT TUESDAY MORNINGFOR SOUTHERN INDIANA.LAT...LON 3992 8595 3988 8595 3988 8596 3964 8597 3964 8610 3963 8611 3964 8650 3982 8652TIME...MOT...LOC 2130Z 264DEG 25KT 3974 8638WIND...HAIL 60MPH 1.00IN\$\$
Member Since: June 28, 2006 Posts: 25 Comments: 8516

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Dr. Jeff Masters' WunderBlog

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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