Irene continues to weaken

By: Dr. Jeff Masters , 8:46 PM GMT on August 26, 2011

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Satellite data and measurements from the Hurricane Hunters show that Irene continues to weaken. A 1:32 pm EDT center fix by an Air Force Reserve aircraft found that Irene's eyewall is still gone, and the central pressure had risen to 951 mb from a low of 942 mb this morning. The winds measured in Irene near the surface support classifying it as a strong Category 1 hurricane or weak Category 2. Satellite imagery shows a distinctly lopsided appearance to Irene's cloud pattern, with not much heavy thunderstorm activity on the southwest side. This is due to moderate southwesterly wind shear of 10 - 20 knots. This shear is disrupting Irene's circulation and has cut off upper-level outflow along the south side of the hurricane. No eye is visible in satellite loops, but the storm's size is certainly impressive. Long range radar out of Wilmington, North Carolina, shows that the outermost spiral bands from Irene have moved ashore over North Carolina. Winds at buoy 41004 100 miles offshore from Charleston, SC increased to 47 mph, gusting to 60 mph at 3 pm EDT, with significant wave heights of 25 feet.


Figure 1. MODIS satellite image of Hurricane Irene taken at 11:50 am EDT Friday August 26, when Irene was a Category 2 hurricane with 105 mph winds. The eyewall collapsed several hours before this image was taken, and no eye is apparent. Image credit: a href=http://rapidfire.sci.gsfc.nasa.gov/gallery/ NASA.


Figure 2. Distribution of Irene's wind field at 3:30 pm EDT Friday August 26, 2011, as observed by the Hurricane Hunters and buoys. The right front quadrant of the hurricane had about 90% of the storm's hurricane-force winds (yellow and warmer colors, bounded by the heavy black line between the "50" and "60" knot thin black lines.) Tropical storm-force winds (heavy black like bounding the light blue area) extended out 290 miles from the center of Irene. Image credit: NOAA/AOML/HRD.

Forecast for Irene
With its eyewall collapsed and just 18 more hours over water before landfall, Irene does not have time to build a new eyewall and intensify. The storm is too large to weaken quickly, and the best forecast is that Irene will be a strong Category 1 hurricane at landfall in North Carolina on Saturday. Based on the latest wind analysis from NOAA's Hurricane Research Division (Figure 2) and Irene's continued weakening trend, I predict that the 80-mile section of North Carolina coast to the right of where Irene makes landfall will receive sustained hurricane-force winds of 75 - 85 mph on Saturday at landfall; the 80-mile section of coast to the left will receive 55 - 75 mph winds. High wind shear of 30 knots will begin ripping into Irene Sunday morning when it is near Southern New Jersey, and more rapid weakening will occur. By the time Irene arrives on Long Island Sunday afternoon, it will probably have top sustained winds in the 65 - 75 mph range. However, since Irene is such a huge storm--tropical storm force winds extend out up to 290 miles from the center--it has set a massive amount of the ocean's surface in motion, which will cause a much larger storm surge than the winds would suggest. At 3:30 pm EDT this afternoon, a wind analysis from NOAA/HRD (Figure 2) indicated that the potential storm surge damage from Irene still rated a 5.0 on a scale of 0 to 6. This is equivalent to the storm surge a typical Category 4 hurricane would have. While this damage potential should steadily decline as Irene moves northwards and weakens, we can still expect a storm surge one full Saffir-Simpson Category higher than Irene's winds when it impacts the coast. Since tides are at their highest levels of the month this weekend due to the new moon, storm surge flooding will be at a maximum during the high tidal cycles that will occur at 8 pm Saturday night and 8 am Sunday morning. Wherever Irene happens to be at those times, the storm surge damage potential will be maximized. I continue to give a 20% chance that a 3 - 4 foot storm surge high enough to over-top the Manhattan flood walls and swamp the New York City subway system will occur on Sunday. The latest 11 am probabilistic storm surge map from NHC shows a 20 - 30% chance of a storm surge in excess of 3 feet in New York Harbor (Figure 4.) Keep in mind that these maps are calculated for normal tide level, and this weekend's high tides will be nearly 1 foot above normal.

Insurance company AIR-Worldwide is estimating that insured damages from Irene in the U.S. will be $1.5 - $6 billion. They estimate losses in the Caribbean at $0.5 - $1.1 billion from Irene.


Figure 3. Storm surge heights, in feet above normal tide level, which have a 20 percent chance of being exceeded during the next 3 days.  The graphic is based upon an ensemble of Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model runs using the current National Hurricane Center (NHC) official hurricane advisory. The exceedance heights depend on the historical accuracy of NHCs forecasts of hurricane track, and wind speed, and an estimate of storm size. Image credit: NOAA.


Figure 4. Overall chance that storm surges will be greater than 3 feet above normal tide levels during the next 3 days.  The graphic is based upon an ensemble of Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model runs using the current National Hurricane Center (NHC) official hurricane advisory.  Storm surge probabilities depend on the historical accuracy of NHCs forecasts of hurricane track, and wind speed, and an estimate of storm size. Image credit: NOAA.

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.

Internet radio show on Irene at 4:30pm EDT
Wunderground meteorologists will be discussing Hurricane Irene on a special edition of our Internet radio show, the Daily Downpour, today (Friday) at 4:30pm EDT. Shaun Tanner , Tim Roche, Angela Fritz, and Rob Carver will take your questions. The email address to ask questions is broadcast@wunderground.com.

Jeff Masters

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Wind has really picked up here in Wilmington, NC. Sideways rain. Finally getting some good action. Time to get the drinks flowing.
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551. 900MB
Recon, anyone? What's the latest?
Member Since: June 11, 2006 Posts: 0 Comments: 660
If she rebuilds her eye and strengthens I am going to be thrilled that the college kid from Alaska had the better forecast than the extremely experienced and educated PhD holder and former H.H. who runs this blog. It is getting to the point where I find Levi to be the best, and least sensational, voice available on the internet regarding tropical systems.
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Quoting GTcooliebai:
That's what I said, this is based on climatology. And FYI Hurricane Ida penetrated the GOM in 2009.

haha ida was in early november and that was an el nino year. at that time the waters in the gulf were below normal than average in terms of temperature so ida didnt get ALOT of juice from the gulf :)
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Sushi, wine and watching the weather TV. The best way to relax after a long week. Cheers.
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Quoting shadoclown45:


Um can i get a link to oz's cam?


check mail :)
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Quoting BahaHurican:
Sure and I've seen ur handle on the blog a few times....

I agree with the data collection. However, I'm also thinking that the Emily track was pretty accurate, despite her "high jinks" and refusal to form. The track through and north of the Bahamas was pretty accurate.

It's the HH data, I think. Whenever they can get readings, NHC does better. Emily did have one of the dropsonde high-level flights.


In total agreement there, Emily could not have been more challenge than she was, and they did do a fantastic job.
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Quoting wxmobilejim:

he has been right about Irene from a week before she formed so I would say he lost his mind. He was saying east coast when everyone else was saying gulf then Florida.

Joe Bastardi , Twitter 21 Aug;

”Irene has developed, and I have no changes... its a Florida/Se threat where the preseason impact forecast was centered”

Didn't he say Florida?
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Quoting FLdewey:


He should be arriving shortly... they won't pop up until they're in position.

He was going to try to get landfall at NC and in NY. With Irene weakening I'd imagine he'll bail on the NYC.


Last I heard the D2 lost its AC somewhere heading into North Carolina. Can that big red shoe float?
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Link
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Quoting weatherrx:
Just what I thought a global warming extremist. lol


I didn't say anything about global warming, ice is getting thinner though, why? not gonna speculate.
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539. JLPR2
Gap of dry air just north of the core.
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Quoting wolftribe2009:
EYEWALL might be re-forming. Last frame on the rainbow shows cloud tops getting colder which is evident by the deeper reds showing up. Then you see a hole in the middle of the storm where the cent er is.

Hard to say it is the eye but we could be in form her making a come back

Link


Can't go frame by frame with tropical systems. Convection always pulses up and down. Just like the storm motion its about long term trends. She looks about the same cloud pattern wise and inner core wise as she did 3 hours ago...maybe a little colder cloud tops in the partial inner eyewall but has not reflected in a pressure fall or wind increase yet.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting FLdewey:
iMap tracker showing some good free video out there... ChaserTV and TVN both show iMap streamers.


Yep. I'm watching. Where's Reed Timmer?
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Good night Irene's eye:

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Quoting NoVaForecaster:


I can see the dry air wedge going in on those two images. The dry air is affecting the system negatively right now, no doubt about that. However, deep convection is appearing at the center, which would not happen if the dry air had penetrated the core. Considering the surrounding airmass the storm is fighting it off rather well.


It is true there is a wet core. But look how small the wet core is getting in the 6:45pm image, and by 7:15pm (the 208.jpg image) the wet portion is perhaps only 60 miles across.

http://rammb.cira.colostate.edu/ramsdis/online/im ages/tropical/207.jpg


http://rammb.cira.colostate.edu/ramsdis/online/im ages/tropical/208.jpg


Combine this with the direction of motion and it means that the really nasty conditions (60+mph sustained winds) may completely miss the populated areas of NC.

Of course the core may develop again but I doubt it will be add to the storm surge we are seeing now. If the core develops again I think it can only happen AFTER Irene is mostly clear of Cape Hatteras.
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Quoting EYEStoSEA:


Yep, I'm listening....


Um can i get a link to oz's cam?
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So who has adopted the old saying, "Me, Myself and Irene?" lol
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Quoting KennyNebraska:
Oz's webcam and audio are fab! Awesome wind sounds!


Yep, I'm listening....
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528. 996tt
Quoting Levi32:
TWC live stream (don't watch for the hype....watch for the reporters on the beaches where we can see what's going on. That's all I watch it for.)


My post right after yours says exactly the same thing.
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Quoting KennyNebraska:
Oz's webcam and audio are fab! Awesome wind sounds!
link pls
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Quoting daddyjames:


Thanks for busting that bubble, next your gonna tell me that Santa Claus doesn't live at the North Pole. Then again, not unless he has a house boat . . .
Just what I thought a global warming extremist. lol
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Just remember in the NE, when a bad blizzard blows there are not leaves on the trees, now you have leaves on the trees with a tropical system, gonna be different ballgame this go around
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Quoting daddyjames:


Baha, lets not forget the unprecedented amount of resources that were thrown at this storm. The track forecast is only a reflection of the large amount of data collected over a very large geographical region. Unfortunately, this is not, and will not, be the case with every storm . . .
BTW, you don't know me but happy to hear that you are doing fine (exception of the power/phone outages).
Sure and I've seen ur handle on the blog a few times....

I agree with the data collection. However, I'm also thinking that the Emily track was pretty accurate, despite her "high jinks" and refusal to form. The track through and north of the Bahamas was pretty accurate.

It's the HH data, I think. Whenever they can get readings, NHC does better. Emily did have one of the dropsonde high-level flights.
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Quoting 996tt:


I believe that has nothing to do with current weather patterns, but prevailing historical patterns. For instance, same thing was applicable in the last two hurricane seasons yet nada for GOM
That's what I said, this is based on climatology. And FYI Hurricane Ida penetrated the GOM in 2009.

Member Since: August 31, 2009 Posts: 0 Comments: 5628
521. 996tt
Haha, TWC is a bunch of kooks. They could drop all of the adjectives, inflection and drama and the same people would still watch. Us weather geeks may even be more inclined to watch. They best thing they have going for them is live forecasting showing storm rolling in so they don't really need all the scare tactics.
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TWC live stream (don't watch for the hype....watch for the reporters on the beaches where we can see what's going on. That's all I watch it for.)
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Oz's webcam and audio are fab! Awesome wind sounds!
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I am curious to see what Irene will look like in the AM when I wake up. Mandatory evacuations all over the place here in southern coastal NJ -- Exit 98 and all exits south will be closed. All East and south bound traffic on Rt. 70, 72, 35, 34, 36 all closed. I already sent my children and their pets to a safer area. I will wait till morning to make my decision on myself.
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Quoting TropicalAnalystwx13:


A moderately deep disturbance in the baroclinic atmosphere located in the western Central Gulf of Mexico???

looks to me a tropical storm interacting with another tropical storm.... bad news for the gulf states but its very far out
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I think Irene has come out to play. I am starting to think this is a real eye forming on her. I don't feel good about the situation if she does form an eye wall again. A strengthening storm is far worse than a weakening storm that has lost it's eye.

Link

Link
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We have weathered many a hurricane and tropical storm, but never in New England. Be careful people.

This storm still has the potential for massive destruction, even though it is diminishing, a little bit. The thought of power outages, lack of food and water, and the many other things that people not used to even a tropical storm are unaware of. It's going to be a rough weekend no matter what happens. Be safe everybody and listen to the warnings.
Kelley and Susan
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Quoting JLPR2:


Models that far out are as real as Tinkerbell.


Thanks for busting that bubble, next your gonna tell me that Santa Claus doesn't live at the North Pole. Then again, not unless he has a house boat . . .
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Quoting TropicalAnalystwx13:


lol, it isn't dark yet...And the winds aren't necessarily hurricane force yet. ;)
Winds are gusting to tropical storm force out here.However me and my commrades will be shooting some footage of the conditions becoming dangerous as the night progresses into the morning.
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511. bwat
Quoting PensacolaDoug:
You don't have 1% percent of his talent. Truth hurts.
Ouch, never claimed to, just call em as I see em. No offense ment.
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509. JLPR2
Quoting weatherrx:
Models that far out have a lottery chance of being right. Is this a case of wish casting I think so.


Models that far out are as real as Tinkerbell.
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508. 996tt
Quoting GTcooliebai:
Look at the contrast from Aug. to Sept. in the GOM, of course this is based off Climatology and may not be the pattern we see coming up.









I believe that has nothing to do with current weather patterns, but prevailing historical patterns. For instance, same thing was applicable in the last two hurricane seasons yet nada for GOM
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Quoting RitaEvac:
WTH is this...




Texas drought buster?????
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Quoting FLdewey:


That was what you told us Emily was going to do.


Yes in my disoriented drougth stricken mode
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good night irene... no, maybe not
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Quoting WeatherNerdPR:

She's so self-centered...


Given everything you've been through this week...that was seriously funny. Nearly spit water on my laptop.
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Quoting JLPR2:


You need to upload the image elsewhere or else it wont be visible to others.
Models that far out have a lottery chance of being right. Is this a case of wish casting I think so.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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