Dr. Jeff Masters' WunderBlog

Irene slightly weaker, but still very dangerous

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

+28

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 An upper-level outflow channel that was open to the south is gone, and has been replaced by shearing winds from the west and southwest that are ripping into the hurricane.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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1351. Dragod66 02:07 GMT le 26 août 2011
Quoting houstongator: Just asking from my lack of knowledge, but can a hurricane get big enough that it won't go to a Cat 4 or Cat 5 because it takes all of its energy in filling out the windfield. It seems Ike was like that - with pressures low, but the wind not representative of the pressure. no meteorologist but typhoon tip (1979) was huge and the most powerful tropical cyclone on record Member Since: 24 août 2011 Posts: 0 Comments: 449

1352. JLPR2 02:07 GMT le 26 août 2011
Quoting RedrumATL: BTW: That Photo by "Debra" up above is an incredible composition for those that enjoy photography! Her photos are always awesome. Member Since: 4 septembre 2007 Posts: 7 Comments: 7491

1353. MississippiWx 02:08 GMT le 26 août 2011
Irene currently has an easterly component in her motion. We'll have to see how long it lasts. Any wobble east is great as long as it doesn't wobble back the same amount or more to the west. Member Since: 15 juillet 2006 Posts: 14 Comments: 8651

1354. redwagon 02:08 GMT le 26 août 2011
Quoting MississippiWx: Ridiculous. Could you imagine being on a boat at the base and looking up at the next wave coming at you? Might as well turn around and kiss your own a goodbye! Katrina had 50+ feet tall waves in the Gulf...That's extraordinary considering how relatively small the Gulf is compared to huge bodies of water like the Atlantic. Ridiculous? Member Since: 4 août 2007 Posts: 0 Comments:** 1444

1355. WeatherNerdPR 02:08 GMT le 26 août 2011
Quoting JLPR2: Yep, my street flooded, thankfully it stopped rising just in time to prevent any damage. Living next to a creek can have its problems. I saw some images of the flooding, looked like Hortense's revenge. Member Since: 7 juillet 2010 Posts: 0 Comments: 5464

1356. NCHurricane2009 02:08 GMT le 26 août 2011
Quoting houstongator: Just asking from my lack of knowledge, but can a hurricane get big enough that it won't go to a Cat 4 or Cat 5 because it takes all of its energy in filling out the windfield. It seems Ike was like that - with pressures low, but the wind not representative of the pressure. In Ike's case...it was interesting...it went through a very very very very slow eye wall replacement cycle as it traveled across the Gulf of Mexico...and hurricanes that undergo slow eye replacements tend to struggle to increase their winds...Irene is sorta like that...she has been going through a very slow eye wall replacement over the last several hours.... Member Since: 15 septembre 2009 Posts: 277 Comments: 3357

1358. victoriahurricane 02:08 GMT le 26 août 2011
Quoting redwagon: Reposting in case anybody missed it. Oh trust me I saw it, approaching 30 feet waves. Has the storm surge of a Cat 3/4, wow. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

1361. SPLbeater 02:09 GMT le 26 août 2011
CAN SOMBODY PLEASE PLEASE GIVE ME THE LINK AND/OR POST THE STORM SURGE POTENTIAL FROM IREN IN NEW HANOVER COUNTY PLEASE? THANKS Member Since: 4 août 2011 Posts: 43 Comments: 3955

1362. TStormSC 02:09 GMT le 26 août 2011
Quoting SCwannabe: My wife just said Charleston county,SC schools closed tomorrow for sprinkles and 25-35 mph winds...are you kidding me. What a bunch of morons Calling for gusts 35-45 tomorrow afternoon. Member Since: 15 juillet 2007 Posts: 6 Comments: 205

1363. amd 02:09 GMT le 26 août 2011
Quoting NCHurricane2009: Well...if those winds don't climb past 115 mph with that low of a pressure...then this is one of the lowest pressures in a minimal cat. 3....Irene continues to have a history for having wind speeds somewhat low for the central pressure observed...hmmmm... Irene does continue to have a double max winds structure on its eastern side. Just checked the latest NOAA recon winds, and the winds have a secondary max at 981 mb of 97 knots (flight level). We will know soon if the eastern eye-wall begins to become more dominant by having stronger winds at the eye-wall compared to the secondary max. Member Since: 29 août 2005 Posts: 0 Comments: 1024

1364. MississippiWx 02:09 GMT le 26 août 2011
Quoting redwagon: Ridiculous? ? I'm confused... I said the wave heights were ridiculous... Member Since: 15 juillet 2006 Posts: 14 Comments: 8651

1366. ConnecticutWXGuy 02:10 GMT le 26 août 2011
Quoting MississippiWx: Irene currently has an easterly component in her motion. We'll have to see how long it lasts. Any wobble east is great as long as it doesn't wobble back the same amount or more to the west. good for NC, bad for New England where there are more people. Member Since: 17 novembre 2010 Posts: 10 Comments: 521

1367. PensacolaDoug 02:10 GMT le 26 août 2011
Quoting StormJunkie: Dang, talk about around your @$$ to get to your elbow...lol When He booked the flight to Tampa the strorm was forecast to come to Florida. He had to make the call Monday where to fly to or the fares would go up. Member Since: 25 juillet 2006 Posts: 0 Comments: 4828

1369. flbeachgirl 02:10 GMT le 26 août 2011
Quoting HurricaneStriker: Has anyone been hearing about the rip currents in Florida? Normally they mention a lot about them in coast storms like Earl but so far I havent heard anything "rip current" on Irene. We were out on Jax Beach today watching the waves. We usually have a moderate-to-high risk of rip currents on a good day. The surfers were describing the water as a "washing machine". Edited to add: Forgot to mention that St. Johns County has actually closed some of their beaches due to the rough surf. Member Since: 24 août 2010 Posts: 0 Comments: 30

1370. MahFL 02:11 GMT le 26 août 2011
The CDO is becoming rather circular again. Member Since: 9 juin 2004 Posts: 0 Comments: 2430

1371. MZT 02:12 GMT le 26 août 2011
Quoting nccanewatcher: I'm in Wilmington. It seems a lot of people aren't taking this serious enough. Staying put probably does make the most sense for the average person on the mainland who does not live in a flood prone area. Riding it out on a barrier island is a different matter though in my mind. Those islands are really little more than sand bars, ready to be rearranged by nature. Member Since: 24 septembre 2005 Posts: 0 Comments: 775

1373. ConnecticutWXGuy 02:12 GMT le 26 août 2011
Quoting NoVaForecaster: Just saw something about when the storm, supposedly now the jet stream will act to help ventilate the storm and keep it stronger as it moves north by increasing outflow on the north/northwest side of the storm. Anyone that can confirm or deny this? this is a result which has popped up in several models from time to time, they seem to slowly be coming into more consensus on this happening which is probably why TWC is bringing it up. We toyed with this theory yesterday in the blog since it looked like a possibility. Member Since: 17 novembre 2010 Posts: 10 Comments: 521

1374. Vero1 02:12 GMT le 26 août 2011
Conditions at Vero Beach: Currently 76.7 °F Mostly Cloudy Heat Index: 99 °F Humidity: 95% Wind: 1.0 mphfrom the West Wind Gust: 17.0 mph Visibility: 8.0 miles Dew Point: 80 °F Precipitation: 68% chance of precipitation Pressure: 29.62 in(Falling Member Since: 21 juillet 2008 Posts: 4 Comments: 2233

1375. NCHurricane2009 02:12 GMT le 26 août 2011
Quoting MississippiWx: Irene currently has an easterly component in her motion. We'll have to see how long it lasts. Any wobble east is great as long as it doesn't wobble back the same amount or more to the west. It seems she has been heading straight north since she left Abaco Island....and that puts her a hair east of the center of the NHC track...so I am still inclined to beleive she will track along the immediate NC coast and not go inland like the NGFDL model showed earlier today.... Member Since: 15 septembre 2009 Posts: 277 Comments: 3357

1376. DontAnnoyMe 02:13 GMT le 26 août 2011
Quoting SPLbeater: CAN SOMBODY PLEASE PLEASE GIVE ME THE LINK AND/OR POST THE STORM SURGE POTENTIAL FROM IREN IN NEW HANOVER COUNTY PLEASE? THANKS Link Member Since: 21 septembre 2010 Posts: 1 Comments: 3690

1377. MississippiWx 02:13 GMT le 26 août 2011
Quoting ConnecticutWXGuy: good for NC, bad for New England where there are more people. True...NC would knock her down some. Member Since: 15 juillet 2006 Posts: 14 Comments: 8651

1378. RedrumATL 02:13 GMT le 26 août 2011
Quoting P451: After some additional struggles this evening the eye has cleared back out and the CDO seems to be strengthening and wrapping around with colder tops. AVN Color Enhanced IR Water vapor Oh, your back. Want to comment on the "jet streak" prediction by TWC? I'm waiting for others to comment. Member Since: 17 août 2011 Posts: 0 Comments: 106

1379. owntime 02:13 GMT le 26 août 2011
Has anyone heard from Granpa? I hope he took the warnings and go out of there. Member Since: 28 septembre 2007 Posts: 0 Comments: 87

1380. Dennis8 02:14 GMT le 26 août 2011
BUXTON, N.C. (AP) "One of my greatest nightmares was having a major hurricane go up the whole Northeast Coast," Max Mayfield, the center's retired director, told The Associated Press. He said the damage will probably climb into billions of dollars: "This is going to have an impact on the United States economy." The head of the Federal Emergency Management Agency said damages could exceed most previous storms because so many people live along the East Coast and property values are high. "We've got a lot more people that are potentially in the path of this storm," FEMA Director Craig Fugate said in an interview with The Associated Press. "This is one of the largest populations that will be impacted by one storm at one time." The storm would "have a lot of impact well away from the coastline," he added. "A little bit of damage over big areas with large populations can add up fast." Irene was massive, with tropical-force winds extending almost twice as far as normal, about the same size as Katrina, which devastated New Orleans in 2005. Member Since: 15 août 2008 Posts: 0 Comments: 441

1383. SarasotaToo 02:14 GMT le 26 août 2011
Quoting MississippiWx: Ridiculous. Could you imagine being on a boat at the base and looking up at the next wave coming at you? Might as well turn around and kiss your own a goodbye! Katrina had 50+ feet tall waves in the Gulf...That's extraordinary considering how relatively small the Gulf is compared to huge bodies of water like the Atlantic. I was on a cruise ship during category 4 Eduordo in '96. 40' + swells - you don't want to be there... Member Since: 27 juillet 2008 Posts: 0 Comments:** 33

1384. TampaSpin 02:15 GMT le 26 août 2011
Quoting PensacolaDoug: When He booked the flight to Tampa the strorm was forecast to come to Florida. He had to make the call Monday where to fly to or the fares would go up. I was suppose to have hooked up with him......but, i had made other plans before his flight......i had already bought some tickets to the RAYS game today with the family and had other plans after the game. What time did he end up leaving for Carolina. Member Since: 2 septembre 2007 Posts: 175 Comments: 19747

1385. StormJunkie 02:15 GMT le 26 août 2011
Evening CW :) Good to see ya, been a while! Quoting SCwannabe: My wife just said Charleston county,SC schools closed tomorrow for sprinkles and 25-35 mph winds...are you kidding me. What a bunch of morons Couple of things to think about there. 1st, as Press just pointed out to me, we are due for a 2' astronomical tide tomorrow...Add on anything that Irene piles up (large storms push a lot of water around even if the winds aren't Cat 4...Think Ike.) 2nd, Charleston County is a slew of bridges on marsh. They close many of those bridges when winds reach 40 mph I believe. Want your kids at school when they decide they have to close the bridges? Member Since: 17 août 2005 Posts: 26 Comments: 15218

1386. leftlink 02:15 GMT le 26 août 2011
Quoting aislinnpaps: I was there for Gloria. I don't know a single person who prepared for her. Sad, but true. In Boston this is true, I was in school at the them; however the storm was disintegrated in its final approach to the NE if I remember correctly. According to wikipedia: "Gloria then struck Cape Hatteras, North Carolina early on September 26, with winds of 105 mph (170 km/h) and a pressure of 942 mbar while accelerating to the northeast. Gloria became the strongest recorded hurricane to strike the U.S. East Coast so far north, a distinction it still holds." http://en.wikipedia.org/wiki/Hurricane_Gloria It looks like Irene is now reaching Gloria's pressure; the only thing is, Irene is hundreds of miles wider and pushing far more water. Member Since: 28 décembre 2010 Posts: 0 Comments: 100

1387. ShenValleyFlyFish 02:15 GMT le 26 août 2011
Quoting PensacolaDoug: When He booked the flight to Tampa the strorm was forecast to come to Florida. He had to make the call Monday where to fly to or the fares would go up. Nobody ever claimed he was the sharpest tool in the shed. LOL Gotta love him. Member Since: 9 septembre 2007 Posts: 36 Comments: 4684

1388. TomTaylor 02:15 GMT le 26 août 2011
Quoting P451: The Perfect Storm in 91 put 100 foot waves in the North Atlantic in the open sea. We had 30 foot waves pouring over the sea wall in Sea Bright in New Jersey. Witnessed it first hand. Storm Surge is nothing to fool with. Storm surge and waves are two different things. That buoy redwagon posted were the open ocean wave heights. Member Since: 24 août 2010 Posts: 18 Comments: 3911

1392. bassis 02:15 GMT le 26 août 2011
Quoting SPLbeater: CAN SOMBODY PLEASE PLEASE GIVE ME THE LINK AND/OR POST THE STORM SURGE POTENTIAL FROM IREN IN NEW HANOVER COUNTY PLEASE? THANKS I found this with a quick google. not good with posting links http://www.nhc.noaa.gov/psurgegraphics_at4.shtml? gm Member Since: 8 septembre 2008 Posts: 0 Comments: 422

1393. IFuSAYso 02:15 GMT le 26 août 2011
Quoting FLdewey: The mother of all Charlie Foxtrots. Roger that. Member Since: 8 Mars 2011 Posts: 0 Comments: 127

1394. Cat5Hurricane250 02:16 GMT le 26 août 2011
937.2 mb (~ 27.68 inHg) Member Since: 4 août 2010 Posts: 0 Comments: 101

1395. Zaphod 02:16 GMT le 26 août 2011
Hmmm....west side is still under shear it seems. Looks to be consistently a bit east of track for a change too. Too soon to see if it's a wobble or a deviation of track, though. Member Since: 5 octobre 2005 Posts: 15 Comments: 3239

1397. RedrumATL 02:16 GMT le 26 août 2011
Quoting P451: After some additional struggles this evening the eye has cleared back out and the CDO seems to be strengthening and wrapping around with colder tops. AVN Color Enhanced IR Water vapor And I've asked the blog for a guesstimate of diameter on that eye. No response yet. Do you know? Thanks, Redrum Member Since: 17 août 2011 Posts: 0 Comments: 106

1398. HiWay 02:16 GMT le 26 août 2011
Quoting Sflabuck: trust me, this is a fish storm .. stop panicking ... i wasted monies on beef jerky and red wine here in Boca to ride out this fishy More like a beached whale. Member Since: 17 août 2007 Posts: 0 Comments: 55

1399. tpabarb 02:16 GMT le 26 août 2011
Quoting nccanewatcher: I'm in Wilmington. It seems a lot of people aren't taking this serious enough. School was just cancelled, my guess is because Carolina Beach will call for a mandatory evacuation tomorrow morning, they need the shelters. A lot of people on Carolina Beach aren't going to leave because after Fran they weren't allowed back for a couple of weeks. A lot of people got mad and said they'd never leave again. I hope they decide to leave. I'm in Wilmington too, and I feel kind of like an idiot for leaving, but I don't really see what benefit staying has? I keep wavering. Now that it's going to hit us during the day I'm considering staying...but, what if a tree falls on the house? I'd rather be 2.5 hours west! I dunno...are you leaving? Member Since: 20 octobre 2005 Posts: 0 Comments: 52

1400. redwagon 02:17 GMT le 26 août 2011
Quoting victoriahurricane: Oh trust me I saw it, approaching 30 feet waves. Has the storm surge of a Cat 3/4, wow. That graph kinda numbed me. As in we might be referring to the Outer Banks as Back When Banks in a couple days. On the ? bright side, that buoy is apparently very close to the eyewall right now. Member Since: 4 août 2007 Posts: 0 Comments: 1444

1401. MississippiWx 02:17 GMT le 26 août 2011
Quoting Cat5Hurricane250: 937.2 mb (~ 27.68 inHg) Wow... Member Since: 15 juillet 2006 Posts: 14 Comments: 8651

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