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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This looks to be good news. Still weakening. Is TWC kooks still call this the storm of the century and catostrophic? Haha. Someone needs to go to Duck Island and give Stephanie Abrahms a wedgie.
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Looks like another hurricane around september 5th as per the ecmwf and another brewing in the Gulf around the same time
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Quoting AstroHurricane001:
Believe it or not, the Outer Banks area has not seen a cat. 3 major hurricane landfall in 112 years.



Hurricane San Ciriaco, August 3 - September 4, 1899


That Hurricane did everything it seems.
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I just turned to the weather channel and Jim Cantore is calling Irene "the perfect storm"..
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Quoting TropicalAnalystwx13:
Power flickers, don't know how much longer I can stay on.


gOODBYE
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Quoting TropicalAnalystwx13:
Power flickers, don't know how much longer I can stay on.
Stay safe 13 ...:)
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Quoting TropicalAnalystwx13:
All I can say is wow...I'm in for a long night.


Where are you located?
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Quoting Levi32:
Recon just found extrapolated 950mb pressure in Irene's eye.
down 1mb from 951. this mean she is maintaining herself or starting to slowly reorganize?
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All I can say is wow...I'm in for a long night.
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Quoting CybrTeddy:


I don't think you understand.

WATER IS the main problem with Irene.

Why do you think Ike was so bad? The surge.

Irene is generating massive surge, that could be very bad for NYC and NC.
I do understand storm surge I am from south la my house went under 14 feet of water. With that being said NC may have to deal with storm surge, the surge will be not that big by the time whatever is left of the circulation get to the mid atlantic and north.
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don't feed the trolls
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Believe it or not, the Outer Banks area has not seen a cat. 3 major hurricane landfall in 112 years.



Hurricane San Ciriaco, August 3 - September 4, 1899
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Quoting sunlinepr:
Good injection of Dry Air, Irene degrading... Good news...



Outer band effect, but the center appears to have recovered from earlier today. Note how the last frames are now filled with bright white.
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Guys, its a weakening Cat 2, nothing tooo bad, its Hyped.
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Quoting NoVaForecaster:
Thanks for the update!



Colder cloud tops re-appearing near the center in a circular shape. Possibly a formation of a new eyewall?


yea I am thinking that she might try to strengthen again. I know a lot of the models were showing her strengthening north of NC all last week.
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While IRENE has no core, she can start developing one - I am still not ready to say she won't get better organized tonight. Has a LOT of dry air to deal with but night time is a perfect opportunity to fire off some convection.

I don't think IRENE will strengthen but by becoming better organized tonight through cycling some of the dry air out, she could at least maintain her intensity until landfall.

We shall see.
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Power flickers, don't know how much longer I can stay on.
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So it looks like Wilma in 2005 will continue to be the last Major Hurricane to hit the CONUS. Almost 6 years, but the peak of this season is just getting started and who knows what Sept. and Oct. will bring us.
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Recon just found extrapolated 950mb pressure in Irene's eye.
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From the 5:00 p.m. Eastern NHC discussion:
Recent microwave data and observations from the aircraft indicate that the inner core has eroded. Although Irene will be moving over warm water during the next 12-18 hours...the lack of an inner core will likely preclude any restrengthening. Although not shown in the official forecast...Irene could weaken just below hurricane strength before reaching southern New England. However...impacts from this large tropical cyclone will not be very different if it is a strong tropical storm or low-end Hurricane.
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is there anyone else that believe that Hurricane Irene could be re-structuring and could maintain her strength or even strength a little bit?
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Quoting Floodman:


**POOF!**


Thank you,I was about to do that
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Wow, down to a 31% chance of Irene being a hurricane off the Jersey shore. I wonder if Doc, with all due respect, and the NHC is jumping the gun? But they are the experts.
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Quoting WBNC:
Wrightsville Beach... the waves are huge! but we dodged a huge bullet. She's sucking in dry air...you think our OBX will see only a Cat 1?

I'll post it again... Dr. M's discussion said..." 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."

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i disagree on a cat 1 at landfall. more like a 2 but still really wont matter. impacts will be the same. if the euro pans out to be true irene could restregnthen a little overnight tonight and tomorrow morning as showed on the model run..
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Quoting PensacolaDoug:
Well!
Shiny new blog!
yeah but it won't be long and it will be a mess

thanks doc for update

iam hoping she crosses a little further inland over the nose of NC help weaken it even further its all good weaker the better

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Quoting Bluestorm5:
Hey, good luck with Irene and her wrath... be safe! Going to the game (don't understand why it's not cancelled?).


You too....I don't know either, do they not know there is a hurricane coming? :P
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Quoting Levi32:
Thanks Dr. Masters.

From previous blog:



Well because the shortwave is going to be passing up over southern Canada, encountering strong resistance from the Bermuda ridge over the northwest Atlantic. This will be creating a strong jet just north of New England, and if you look at the jet, it is in a great position to exhaust air from Irene's surface low via the right entrance region. Irene will be approaching New England by that time (48 hours on this GFS image). This should slow the pressure rises a bit, and I believe this is why the global models show Irene remaining very strong until she crosses Long Island.



Thanks for the explanation. Definitely learned something new.
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I just spoke with my daughter in Boston, well she lives outside of Boston in Wellesley..and they have not done a thing to get ready for this storm and the power outtage they will probably have Sunday & Monday if not longer..

She was not aware they were in any type of danger at all! YIKES!

I gave her instructions to prepare to be without power.. I don't care if she and her husband have to suffer a little because they are not prepared but they have my 3 yr old Grandson and 2 grand dogs!
The grandson & granddogs must be taken care of!
LOL
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I tell you...These outer bands pack quite a punch.
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good news, hope it doesn't make people on further up the east coast too complacent.
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Quoting TropicalAnalystwx13:
Thanks Dr. Masters.

Meanwhile...That was a strong gust.
Hey, good luck with Irene and her wrath... be safe! Going to the game (don't understand why it's not cancelled?).
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Good injection of Dry Air, Irene degrading... Good news...

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From NHC AT 5pm

.THE LACK OF AN INNER CORE WILL LIKELY PRECLUDE
ANY RESTRENGTHENING. ALTHOUGH NOT SHOWN IN THE OFFICIAL
FORECAST...IRENE COULD WEAKEN JUST BELOW HURRICANE STRENGTH BEFORE
REACHING SOUTHERN NEW ENGLAND.

As i was saying a few hours ago... she has no core..
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Thanks Dr. I appreciate the updates.
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15. WBNC
Wrightsville Beach... the waves are huge! but we dodged a huge bullet. She's sucking in dry air...you think our OBX will see only a Cat 1?
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Thanks Dr. Masters...

looking at wind field map on NHC page if this storm goes DUE NORTH through NC (which is very unlikey)
, Greenboro can get TS force winds all the way to 100 miles offshore of Cape Hatteras... that's one huge wind field.
However, the storm is likely to curve a bit so maybe the TS winds can go as far west as Durham?
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Quoting CybrTeddy:


I don't think you understand.

WATER IS the main problem with Irene.

Why do you think Ike was so bad? The surge.

Irene is generating massive surge, that could be very bad for NYC and NC.


Wasted breath, teddy; trolls are trolls
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Quoting weatherrx:
It appears Irene will strugle to maintain cat 1 status
before landfall. She will just be a big rainmaker for the east coast.


Did you miss this part of Dr.M discussion..."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."
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just over 1 inch of rain and a pressure drop from 1009 to 999 in the last 4 hours here in Surfside Beach,SC.
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Quoting weatherrx:
It appears Irene will strugle to maintain cat 1 status
before landfall. She will just be a big rainmaker for the east coast.


I don't think you understand.

WATER IS the main problem with Irene.

Why do you think Ike was so bad? The surge.

Irene is generating massive surge, that could be very bad for NYC and NC.
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Thanks Dr. Masters.

Meanwhile...That was a strong gust.
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Quoting weatherrx:
It appears Irene will strugle to maintain cat 1 status
before landfall. She will just be a big rainmaker for the east coast.


**POOF!**
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Well at 4:50, just had a rain band pass through Wilmington NC...Wind was ENE 42+ 52 KTs with heavy rain... vis about 1/4 mile...have white caps in the ICW... wind has now dropped of to 31 Kts,
We are 2 hours until high tide and the level is already above normal.
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Thanks Dr. Masters.

From previous blog:

Quoting IceCoast:


Can you dive into this a little bit further. I've heard a few people say it but don't really understand it. Does it have to do with the storms forward motion? Another feature in the atmosphere that will keep the pressure gradient strong?


Well because the shortwave is going to be passing up over southern Canada, encountering strong resistance from the Bermuda ridge over the northwest Atlantic. This will be creating a strong jet just north of New England, and if you look at the jet, it is in a great position to exhaust air from Irene's surface low via the right entrance region. Irene will be approaching New England by that time (48 hours on this GFS image). This should slow the pressure rises a bit, and I believe this is why the global models show Irene remaining very strong until she crosses Long Island.

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Thank you Dr. M
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It appears Irene will strugle to maintain cat 1 status
before landfall. She will just be a big rainmaker for the east coast.
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950mb
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Continued weakening is a good thing--again, so long as people don't grow complacent and believe all danger has passed...
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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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