Dr. Jeff Masters' WunderBlog

Irene slightly weaker, but still very dangerous

Posted by: Dr. Jeff Masters, 20:59 GMT le 25 août 2011

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An Air Force Reserve hurricane hunter aircraft investigating Irene has found a slightly weaker storm. As of 4pm EDT, the strongest surface winds seen by the aircraft with their SFMR instrument were 91 mph in the storm's northeast eyewall. Highest winds measured at their flight level of 10,000 feet were 114 mph. Assuming the aircraft missed sampling the strongest winds of the hurricane, it's a good guess that Irene has fallen to Category 2 strength with 100 - 105 mph winds, even though the official advisory is higher. The aircraft noted that the eyewall was missing a large chunk on it southwest side, but the central pressure was about the same as early this morning, 950 mb. Satellite imagery from late this morning and early this afternoon showed a distinctly lopsided appearance to Irene's cloud pattern, with not much heavy thunderstorm activity on the southwest side. This was due to moderate wind shear of 10 - 20 knots due to upper-level winds out of the southwest. This shear was able to disrupt Irene's circulation while it was attempting to complete an eyewall replacement cycle, resulting in dry air getting wrapped into the core, which can be seen as a streak of darker clouds in this morning's MODIS satellite image (Figure 1.) satellite loops show that Irene is beginning to recover from this adversity, with a respectable amount of heavy thunderstorms beginning to wrap around to the southwest side from the north. An upper-level wind analysis from the University of Wisconsin CIMSS site shows that Irene's upper-level outflow is much more restricted than was the case 24 hours ago. An upper-level outflow channel that was open to the south is gone, and has been replaced by shearing winds from the west and southwest that are ripping into the hurricane. I think it is 30% likely that Irene will have trouble recovering from this setback, and will not reach the peak intensity of 120 mph winds it had earlier. However, it is more likely that the hurricane will be able to re-establish its upper-level outflow and overcome the shear, based on the latest satellite loops, plus forecasts from the various hurricane models such as the GFDL, HWRF, and ECMWF, which all show Irene at Category 3 strength as it approaches North Carolina on Saturday afternoon.

Figure 1. MODIS satellite image of Hurricane Irene taken at 11:50 am EDT Thursday August 25, when Irene was a Category 3 hurricane with 115 mph winds. The eye of the storm was just off the coast of Abaco Island in the Bahamas. Note the rather squashed appearance of the hurricane, with less heavy thunderstorms on its southwest side. Upper level winds of 10 - 20 knots out of the southwest were eating away at the clouds on this side, and you can see that this shear helped drive some dry air into the hurricane, which can be seen as a darker strip of cloud spiraling into the center from the south, around the east side, then into the center along the northwest side of the storm. Image credit: a href=http://rapidfire.sci.gsfc.nasa.gov/gallery/ NASA.

Irene likely to bring destructive fresh water flooding
In this morning's post, I highlighted the threat from storm surge flooding, but flash flooding and river flooding from Irene's torrential rains are also a huge threat. The hurricane is expected to bring rains in excess of 12" to 100-mile swath from Eastern North Carolina northwards along the coast, through New York City. The danger of fresh water flooding is greatest in northern New Jersey, Southeast Pennsylvania, and Southeast New York, where the soils are saturated from heavy August rains that were among the heaviest on record. At Philadelphia, rainfall so far this August has been 13 inches, not far from the record for rainiest month of all-time, the 15.82" that fell in August 1867. This record will almost certainly be broken when Irene's rains arrive. In general, the heaviest rains will fall along the west side of the hurricane's track, and the greatest wind damage will occur on the east side. Right now, it does not appear that tornadoes will be a major concern, but there will probably be a few weak tornadoes. Hurricane Bob of 1991, the last hurricane to affect New England, spawned six tornadoes, most of them weak F-0 and F-1 twisters.

Figure 2. Predicted rainfall for the 5-day period ending at 8 am EDT Tuesday August 30, as issued by NOAA/HPC.

Latest forecast for Irene
The latest set of model runs don't show any major changes to Irene's track or intensity. Irene will bring damaging winds, torrential rains, and an extremely dangerous storm surge to the coast, affecting a huge area of the mid-Atlantic and New England. Take this storm seriously! Expect widespread disruptions to electric power, transportation, and water systems. Be prepared for many days without power, as utility crews will be overwhelmed with the damage. Irene is capable of inundating portions of the coast under 10 - 15 feet of water, to the highest storm surge depths ever recorded. I strongly recommend that all residents of the mid-Atlantic and New England coast familiarize themselves with their storm surge risk. The best source of that information is the National Hurricane Center's Interactive Storm Surge Risk Map, which allows one to pick a particular Category hurricane and zoom in to see the height above ground level a worst-case storm surge may go. If you prefer static images, use wunderground's Storm Surge Inundation Maps. If these tools indicate you may be at risk, consult your local or state emergency management office to determine if you are in a hurricane evacuation zone. Mass evacuations of low-lying areas along the entire coast of New Jersey, Delaware, Maryland, and Virginia are at least 50% likely to be ordered by Saturday. The threat to the coasts of New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, and Maine is less certain, but evacuations may be ordered in those states, as well. Irene is a very dangerous storm for an area that has no experience with hurricanes, and I strongly urge you to evacuate from the coast if an evacuation is ordered by local officials. My area of greatest concern is the coast from Ocean City, Maryland, to Atlantic City, New Jersey. It is possible that this stretch of coast will receive a direct hit from a slow-moving Category 2 hurricane hitting during the highest tide of the month, bringing a 10 - 15 foot storm surge.

Links
For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Wunderblogger Mike Theiss is in Nassau, documenting the storm's impact on the Bahamas.

Jeff Masters

Irene Rainband from downtown Ft. Lauderdale (pho)

8/25/11 0910 local time.

HurricaneIreneIsOutThere! (trigirl)

Early at the beach to snap the waves from Hurricane Irene east of our coast, the wind was unreal with thunderclouds rolling in with lots of rain for the day.

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201. barbamz 21:48 GMT le 25 août 2011
Dry air wrapping around the core. Member Since: 25 octobre 2008 Posts: 24 Comments: 1572

203. EastTexJake 21:48 GMT le 25 août 2011
Quoting leftlink: If the trend continues, Irene's max wind will drop to 74mph, central pressure will drop to 925mb, and the wind field will expand to 500 miles wide :) Yeah, perhaps it's time for a new way of deciding Hurricane catagories. Member Since: 24 septembre 2005 Posts: 0 Comments: 127

204. Cotillion 21:48 GMT le 25 août 2011
For coincidence: Since 1869, there have been six hurricanes hitting New England as Cat 2 or Cat 3 (never been higher than that). Counting this as the seventh, it is roughly a hit of that intensity every twenty years. It's been twenty years since Bob. Of course, probability isn't a factor in long term landfall estimates. Now, some set ups can cause more of a bias toward East Coast threats as opposed to the Gulf, for example, over a longer period of time than a year. It's not like earthquakes (or volcanoes, to an extent) where an area can be due for one as it's a measure of pressure over time. Member Since: 23 août 2008 Posts: 7 Comments: 5300

205. victoriahurricane 21:48 GMT le 25 août 2011
Quoting leftlink: If the trend continues, Irene's max wind will drop to 74mph, central pressure will drop to 925mb, and the wind field will expand to 500 miles wide :) It's already near 500 miles wide now. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

206. Titoxd 21:48 GMT le 25 août 2011
Quoting franck: But if the convection circles to the west and there is less fuel to the west due to land mass, wouldn't that create a 'pull' to the north/east overall? In theory it could, but Irene is far enough from the coast for that to be too large of an effect. Also, the Gulf Stream is west of the eye, which will enhance the development of thunderstorms in the western semicircle of Irene. (Last image before Irene's clouds began to block the satellite and make the pictures useless) Member Since: 28 juin 2010 Posts: 0 Comments: 241

207. charlottefl 21:48 GMT le 25 août 2011
Quoting TropicalAnalystwx13: Irene's eye is clearing out. We have a closed eye wall now? Member Since: 18 décembre 2006 Posts: 7 Comments: 2672

208. beell 21:49 GMT le 25 août 2011
Selected dropsonde locations from Gonzo's current flight (Mission 22). 500mb heights and a guess at 500mb contours indicated. No surprises on track here if close to correct-north. Similar posted interpretations yesterday and early this morning seemed to hold true, fwiw. click to enlarge Member Since: 11 septembre 2007 Posts: 124 Comments: 12812

209. HappySkeptic 21:49 GMT le 25 août 2011
Link NOAA National Data Bouy Center Canaveral East Bouy will be a good one to watch for Irene's surface impacts for the next 12 hours..... Member Since: 22 août 2011 Posts: 0 Comments: 9

210. 53rdWeatherRECON 21:49 GMT le 25 août 2011
I must congratulate Everybody on the blog today for not mentioning the "dreaded" pinhole eye. But I believe that is in fact what might replace the old eye. Member Since: 5 août 2005 Posts: 2 Comments: 74

211. DallasGumby 21:49 GMT le 25 août 2011
Quoting Gumbogator: This could wind up being the Northeast version of Katrina. Large storms take a long time to spin down. I hope "cake boss" will be o.k. Looks like plenty of roof damage will be a reality!! Or, it could be the Northeast version of Don. But, I suspect it will be neither. I am amazed that Katrina is everyone's benchmark, as if that had never happened before. But, before Katrina, there was Andrew. Before Andrew, Camille; and, before Camille, Donna. Before Donna, 1938 New England; and, before 1938, there was 1935's Labor Day. Before that, there was Galveston. It's not like we haven't had these types of events before. Member Since: 22 août 2007 Posts: 0 Comments: 376

212. Chicklit 21:49 GMT le 25 août 2011
Just had a squall blow through here along the ECFL coast just north of Canaveral. SHORT TERM FORECAST NATIONAL WEATHER SERVICE MELBOURNE FL 542 PM EDT THU AUG 25 2011 COASTAL VOLUSIA-FLAGLER BEACH TO VOLUSIA- BREVARD COUNTY LINE 20 NM TO 60 NM OFFSHORE-FLAGLER BEACH TO VOLUSIA-BREVARD COUNTY LINE OUT TO 20 NM-INDIAN RIVER-INLAND VOLUSIA-MARTIN-NORTHERN BREVARD-NORTHERN LAKE-OKEECHOBEE-ORANGE-OSCEOLA-SEBASTIAN INLET TO JUPITER INLET 20 NM TO 60 NM OFFSHORE-SEBASTIAN INLET TO JUPITER INLET OUT TO 20 NM-SEMINOLE-SOUTHERN BREVARD-SOUTHERN LAKE-ST. LUCIE-VOLUSIA-BREVARD COUNTY LINE TO SEBASTIAN INLET 20 NM TO 60 NM OFFSHORE-VOLUSIA-BREVARD COUNTY LINE TO SEBASTIAN INLET OUT TO 20 NM- 542 PM EDT THU AUG 25 2011 .NOW...SEVERAL OUTER RAINBANDS FROM HURRICANE IRENE WILL CONTINUE TO PUSH INTO THE COAST THROUGH 7 PM THIS EVENING. THESE RAINBANDS WILL REACH INTO THE INTERIOR PORTIONS OF THE AREA INCLUDING THE ORLANDO METRO...INTERIOR VOLUSIA COUNTY...AND OKEECHOBEE COUNTY. ADDITIONAL STRONG SHOWERS AND POSSIBLY A THUNDERSTORM WITH OCCASIONAL LIGHTNING STRIKES WILL BE POSSIBLE THROUGHOUT THE AREA OUTSIDE OF ANY ORGANIZED RAINBANDS. ANY RAINBANDS THAT MOVE THROUGH WILL CONTAIN TORRENTIAL RAINFALL AND WIND GUSTS BETWEEN 40 AND 50 MPH. $$ Member Since: 11 juillet 2006 Posts: 14 Comments: 10227

213. TomTaylor 21:50 GMT le 25 août 2011
Quoting hurricaneben: Does anyone think there's a chance that Irene will be retired by spring. of course there's a chance Member Since: 24 août 2010 Posts: 18 Comments: 3878

214. TruckingPhotog 21:50 GMT le 25 août 2011
Anybody know how the commercial airlines are preparing for this at PHL EWR and JFK? Member Since: 1 novembre 2004 Posts: 0 Comments: 0

216. ProgressivePulse 21:50 GMT le 25 août 2011
Talk about a close call. Member Since: 19 août 2005 Posts: 5 Comments: 4322

217. Dunkman 21:50 GMT le 25 août 2011
Winds were basically 10 knots stronger in the NE section for the NOAA plane than for the AF HH plane that passed through the same section 40 minutes before. Member Since: 6 février 2010 Posts: 0 Comments: 214

218. miguel617 21:50 GMT le 25 août 2011
Glad we have this trio and the folks flying into Irene. I had the opportunity to get inside Kermit and talk to a team of hurricane hunters when they were here on their tour before hurricane season. True professionals and really nice people. Member Since: 19 janvier 2010 Posts: 0 Comments: 61

219. MississippiWx 21:51 GMT le 25 août 2011
Quoting 53rdWeatherRECON: I must congratulate Everybody on the blog today for not mentioning the "dreaded" pinhole eye. But I believe that is in fact what might replace the old eye. Irene has never really had a large eye that was visible on satellite. The dry air entrainment into the core and just enough southwesterly shear have caused enough disruption to cover the eye. Member Since: 15 juillet 2006 Posts: 13 Comments: 8495

220. NEwatcher 21:51 GMT le 25 août 2011
Quoting HarryMc: Not to mention that we've had several unusually severe ice storms in the past 3 years that have left lots of trees damaged. Add to that the saturated ground and we can have more trees down than we can get rid of. I was looking at what left of the trees from the tornado in MA, and the blue tarps still on some homes today. This is not good for us at all. Member Since: 10 juin 2010 Posts: 0 Comments: 18

221. TropicalAnalystwx13 21:51 GMT le 25 août 2011
Quoting charlottefl: We have a closed eye wall now? Well, if the eye is clearing out, then... :P Member Since: 6 juillet 2010 Posts: 89 Comments: 25128

222. TropicalAnalystwx13 21:52 GMT le 25 août 2011
Quoting 53rdWeatherRECON: I must congratulate Everybody on the blog today for not mentioning the "dreaded" pinhole eye. But I believe that is in fact what might replace the old eye. PINHOLE EYE!!!!!!!!!!! Member Since: 6 juillet 2010 Posts: 89 Comments: 25128

223. charlottefl 21:53 GMT le 25 août 2011
Quoting TropicalAnalystwx13: Well, if the eye is clearing out, then... :P That aint good.. Member Since: 18 décembre 2006 Posts: 7 Comments: 2672

224. Methurricanes 21:53 GMT le 25 août 2011
Irene is larger than Ike last year, by 30 miles. Member Since: 1 août 2011 Posts: 0 Comments: 528

225. victoriahurricane 21:53 GMT le 25 août 2011
Quoting hurricaneben: Does anyone think there's a chance that Irene will be retired by spring. I think unless she goes out to sea and doesn't hit the mainland U.S. it is a guarantee she will be retired and one of if not the costliest hurricanes in history. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

227. jascott1967 21:54 GMT le 25 août 2011
Quoting flasooner: Healthy feeder band moved through WPB about an hour ago. Just got my Internet service back. :) Yes, I saw it from the Earthcam - PB Cam. Looked pretty hairy. Member Since: 16 août 2007 Posts: 0 Comments: 516

228. MiamiHurricanes09 21:54 GMT le 25 août 2011
Updated 14 minutes ago. Eye's clearing out, should continue to intensify. Winds will eventually catch up with the 948mb pressure because right now all Recon is finding is in the mid-cat 2 range. Member Since: 2 septembre 2009 Posts: 129 Comments: 19976

229. charlottefl 21:54 GMT le 25 août 2011
Motion over the last 6 hours smoothing all the wobbles has been roughly due N..(roughly) Member Since: 18 décembre 2006 Posts: 7 Comments: 2672

230. StormHype 21:54 GMT le 25 août 2011
Time to fly 'em in NC! Link Member Since: 31 mai 2007 Posts: 0 Comments: 1163

231. MrstormX 21:54 GMT le 25 août 2011
Quoting Methurricanes: Irene is larger than Ike last year, by 30 miles. Of course it was, since there was no Ike last year. Member Since: 27 mai 2009 Posts: 0 Comments: 4221

232. TomTaylor 21:55 GMT le 25 août 2011
Time: 21:25:00Z Coordinates: 27.6333N 76.55W Acft. Static Air Press: 751.8 mb (~ 22.20 inHg) Acft. Geopotential Hgt: 2,301 meters (~ 7,549 feet) Flt. Lvl. Wind (30s): From 147 at 110 knots (From the SSE at ~ 126.5 mph) Flight level winds picking up. Still don't support cat 3 surface winds, however. SFMR surface estimate was only at 83.6MPH for this observation as well. Member Since: 24 août 2010 Posts: 18 Comments: 3878

233. HarryMc 21:55 GMT le 25 août 2011
Quoting NEwatcher: I was looking at what left of the trees from the tornado in MA, and the blue tarps still on some homes today. This is not good for us at all. At least we're ahead of the game on utility crews coming in from as far away as Tennessee. At least they will have extra crews around... remember the outages of 2008 and 2009? Just ice storm and a Nor'easter but I had no power over a week each time. Member Since: 30 Mars 2010 Posts: 4 Comments: 325

234. charlottefl 21:56 GMT le 25 août 2011
Quoting HarryMc: At least we're ahead of the game on utility crews coming in from as far away as Tennessee. At least they will have extra crews around... remember the outages of 2008 and 2009? Just ice storm and a Nor'easter but I had no power over a week each time. I saw Pike crews out and about down here in FL, so they're probably headed that way.. Member Since: 18 décembre 2006 Posts: 7 Comments: 2672

235. victoriahurricane 21:56 GMT le 25 août 2011
Quoting 53rdWeatherRECON: I must congratulate Everybody on the blog today for not mentioning the "dreaded" pinhole eye. But I believe that is in fact what might replace the old eye. That eye is 30 miles wide, that ain't no pinhole. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

236. quakeman55 21:56 GMT le 25 août 2011
Quoting MrstormX: Of course it was, since there was no Ike last year. Or the year before... Member Since: 31 Mars 2002 Posts: 1 Comments: 1276

237. Methurricanes 21:56 GMT le 25 août 2011
Quoting MrstormX: Of course it was, since there was no Ike last year. sorry Ike of 2008, Irenes tropial storm force wind radii is 30 miles greater than Ike's. Member Since: 1 août 2011 Posts: 0 Comments: 528

238. TropicalAnalystwx13 21:56 GMT le 25 août 2011
Quoting MiamiHurricanes09: Updated 14 minutes ago. Eye's clearing out, should continue to intensify. Winds will eventually catch up with the 948mb pressure because right now all Recon is finding is in the mid-cat 2 range. Like Alex - Pressures in the 940s mb, but winds only at Category 2. Winds will catch up overnight though, as Irene has no limit. Member Since: 6 juillet 2010 Posts: 89 Comments: 25128

239. petewxwatcher 21:56 GMT le 25 août 2011
How does Irene rate on the Integrated Kinetic Energy scale? Member Since: 24 Mars 2011 Posts: 3 Comments: 392

240. wunderweatherman123 21:56 GMT le 25 août 2011
Quoting MiamiHurricanes09: Updated 14 minutes ago. Eye's clearing out, should continue to intensify. Winds will eventually catch up with the 948mb pressure because right now all Recon is finding is in the mid-cat 2 range. how strong u think irene will get? Member Since: 23 août 2011 Posts: 0 Comments: 833

241. TropicalAnalystwx13 21:57 GMT le 25 août 2011
Quoting MrstormX: Of course it was, since there was no Ike last year. LOL. Member Since: 6 juillet 2010 Posts: 89 Comments: 25128

242. HarryMc 21:57 GMT le 25 août 2011
Quoting charlottefl: I saw Pike crews out and about down here in FL, so they're probably headed that way.. I think they're headed for New Jersey. The TN crews are headed to New Hampshire/Mass. Member Since: 30 Mars 2010 Posts: 4 Comments: 325

243. MrstormX 21:57 GMT le 25 août 2011
Quoting Methurricanes: sorry Ike of 2008, Irenes tropial storm force wind radii is 30 miles greater than Ike's. Don't worry, just messing with you. Member Since: 27 mai 2009 Posts: 0 Comments: 4221

244. ShenValleyFlyFish 21:57 GMT le 25 août 2011
Quoting Orcasystems: As much as I know this would be a really stupid and dangerous idea... love to be at Peggy's Cove when this thing passes. They had a pretty good web cam there. I watched a storm on it, can't remember which but big blow was at night as I recall. Member Since: 9 septembre 2007 Posts: 36 Comments: 4684

245. TomTaylor 21:57 GMT le 25 août 2011
Eye still looks open to the NE on radar Member Since: 24 août 2010 Posts: 18 Comments: 3878

246. beell 21:57 GMT le 25 août 2011
Quoting wxobsvps: my guess is those heights on the east coast are actually the western extent of the atl high, i.e. no break in the 588 just yet. Could be. Picking a height to delineate a break is a bit iffy. But wv might indicate a portion of the edge of the western ridge. Gotta be there somewhere Link Member Since: 11 septembre 2007 Posts: 124 Comments: 12812

247. WeatherNerdPR 21:57 GMT le 25 août 2011
Hey, this is this blog's 1900th entry! Yipee! Member Since: 7 juillet 2010 Posts: 0 Comments: 5464

249. Cotillion 21:58 GMT le 25 août 2011
Quoting Methurricanes: sorry Ike of 2008, Irenes tropial storm force wind radii is 30 miles greater than Ike's. Ike had a greater hurricane windforce radii, 120 miles to 80 with Irene, though. Member Since: 23 août 2008 Posts: 7 Comments: 5300

250. MiamiHurricanes09 21:58 GMT le 25 août 2011
Quoting TropicalAnalystwx13: Like Alex - Pressures in the 940s mb, but winds only at Category 2. Winds will catch up overnight though, as Irene has no limit. Very large cyclone as well...takes time to spin up. Very similar to Alex in that aspect. Quoting wunderweatherman123: how strong u think irene will get? I'm thinking [low-end] category 4 status. Member Since: 2 septembre 2009 Posts: 129 Comments: 19976

251. charlottefl 21:59 GMT le 25 août 2011
Well I was gonna check the microwave, but look what happens at the end? Ain't that swell? Member Since: 18 décembre 2006 Posts: 7 Comments: 2672

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