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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NOAA airplane is ringing in with 949mb extrapolated pressure. Another vortex message should be out shortly. Winds north of the eye are still below 100kts at flight-level, weaker than earlier.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Time: 21:35:30Z
Coordinates: 31.7667N 77.2667W
Acft. Static Air Press: 752.8 mb (~ 22.23 inHg)
Acft. Geopotential Hgt: 2,048 meters (~ 6,719 feet)
Extrap. Sfc. Press: 949.0 mb (~ 28.02 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 344° at 9 knots (From the NNW at ~ 10.3 mph)
Air Temp: 19.3°C (~ 66.7°F)
Dew Pt: 17.5°C (~ 63.5°F)
Peak (10s) Flt. Lvl. Wind: 11 knots (~ 12.6 mph)
SFMR Peak (10s) Sfc. Wind: 16 knots (~ 18.4 mph)
SFMR Rain Rate: 1 mm/hr (~ 0.04 in/hr)
(*) Denotes suspect data
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Wow Wrightsville Beach water is over the dunes already. Swimmer missing (another Darwin award winner).
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At 5 EDT buoy 41013, which is located 20 miles SE of Cape Fear NC is Reporting:
Wind NE 41+50 KTS waves 23.6 ft. from the ESE
Press. 994.3 and falling.
Waves in the ICW are running about 3 feet with white caps. They are breaking over my bulkhead which is about 2 feet above a normal high.
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cybrteddy.... you are correct on that!!...
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Quoting BahaHurican:
Afternoon all. Back again after another round of power and phone outages.... sure hope I've seen the last of that for a VERY long time...

Will go back and read, but I'm glad to see that Irene seems to be decreasing in intensity. A large and intense tropical system is not what the EC US needs right now.

Hope all the NC and SC and VA and MD and NJ and NY and .... well hope all u guys are prepped and ready.


Welcome back...
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Houston wasnt Bolivar by a lonnnnnng shot.

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ACE at 29.7, 16.6 of that from Irene.
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Quoting QacarXan:
Is Irene going to re-form her eye? What are the odds?
Well, as long as the casinos are closed I guess it's up to me to set the line. I'll say it's a 4/1 shot(trying to take ez money from the "exuberants"....lol)
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Quoting AstroHurricane001:
For better or for worse, long-range computer model forecasts a week ahead show a strong high pressure system centered over Eastern Canada and a trough in the central CONUS. This could drive some hurricane tracks toward South Florida, Louisiana or say, Texas, especially as several highs are seen drifting from the Arctic regions toward eastern North America on the longest-range runs.


The Texas ridge is breaking down next weekend....FINALLY. After this weekend where we may break our all time record high of 109 tomorrow or Sunday!
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No -70C tops...if you want to be picky there's 2 pixels of red lol. It's a rather pathetic looking IR presentation of a Cat 2 hurricane.

Member Since: November 24, 2005 Posts: 635 Comments: 26684
The Latest
*Click on images in WU Blog to magnify them (images can be further magnified in the new window by clicking on them)






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Quoting NoVaForecaster:


If it doesn't restrengthen some I am fully prepared to eat some crow. Irene still has some surprises in store for us, IMO.



You never know. I got out of the prediction business a long time ago.
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Quoting BahaHurican:
Afternoon all. Back again after another round of power and phone outages.... sure hope I've seen the last of that for a VERY long time...

Will go back and read, but I'm glad to see that Irene seems to be decreasing in intensity. A large and intense tropical system is not what the EC US needs right now.

Hope all the NC and SC and VA and MD and NJ and NY and .... well hope all u guys are prepped and ready.


Can you take a call?
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Quoting Patrap:
219. presslord

Roger dat..

Almost Hunker down time for many.


HUNKER DOWN.. phrase from Ike as he approached and a local judge here in Houston told us to "HUNKER DOWN"....we laugh at that here. :>) CORNY.
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For better or for worse, long-range computer model forecasts a week ahead show a strong high pressure system centered over Eastern Canada and a trough in the central CONUS. This could drive some hurricane tracks toward South Florida, Louisiana or say, Texas, especially as several highs are seen drifting from the Arctic regions toward eastern North America on the longest-range runs.
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MOREHEAD CITY, N.C. (AP)


"Don't wait. Don't delay," said President Barack Obama, who decided to cut short his summer vacation by a day and return to Washington. "I cannot stress this highly enough: If you are in the projected path of this hurricane, you have to take precautions now."

As the storm's outermost bands of wind and rain began to lash the Outer Banks of North Carolina, authorities in points farther north begged people to get out of harm's way. The hurricane lost some strength but still packed winds of almost 100 mph, and officials feared it could wreak devastation in a region not used to tropical weather.

Hurricane Irene caused extraordinary disruption Friday as it zeroed in for a catastrophic run up the Eastern Seaboard. More than 2 million people were ordered to move to safer places, and New York announced plans to shut down its entire network of subways for the first time because of a natural disaster.
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Quoting longislandJohn:


you are 100 percent correct , the eye wall might not be full but this storm is acting different then normal canes..this is good because areas north (from its current point)will not get beat up..BUT it will be a storm that all in the area should be very aware of....
You're 100% correct, and you can do what you can to let your friends, neighbors know what you know. I'm concerned that the average person up there will be much less concerned since it's winds won't be quite as strong. It's still going to be a very long miserable time for millions....with danger of trees falling on homes and flooding. Most of the area is gonna' be under strong TS winds for 24 hours. And not prepared for an aftermath with no power.
.
.
btw..welcome to posting on the blog
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219. presslord

Roger dat..

Almost Hunker down time for many.
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Quoting AllStar17:
Irene has certainly jogged eastward (NE) over the past few hours.
Link


GOOOD!! hopefully she sustained that course, but it doesnt look seem like it:(
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Afternoon all. Back again after another round of power and phone outages.... sure hope I've seen the last of that for a VERY long time...

Will go back and read, but I'm glad to see that Irene seems to be decreasing in intensity. A large and intense tropical system is not what the EC US needs right now.

Hope all the NC and SC and VA and MD and NJ and NY and .... well hope all u guys are prepped and ready.
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Quoting AllStar17:
A 1 mb pressure difference is really nothing. Irene appears to be trying to hold its own right now.


Whilst a 1mb drop is fairly insignificant in the grand scale of things, the fact that the pressure had been falling quickly, and is now beginning to fall slightly suggest that it may be trying to organise a little.
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For those asking about live coverage WRAL.com will be doing round the clock coverage starting at 4am tomorrow. They have 3 reporters on the coast and one of the best team of mets in the state.

WRAL covers a significant portion of Eastern NC so they will be focused on not just the Raleigh-Durham area.
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Does no one here have any good links to stormchasers or webcams near the possible landfall location? Multiple people have asked this. Any help is appreciated thanks.
Member Since: October 16, 2008 Posts: 0 Comments: 544
Poor 91L doesn't stand a chance against Irene's outflow:

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A 1 mb pressure difference is really nothing. Irene appears to be trying to hold its own right now.
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All this talk about "downgrading," How do you realistically downgrade something this size, given time it will downgrade itself and in the meantime its going to drop 10+inches of rain doing so along with all sorts of other damage. At the end of the day, or days a downgrade wont affect the real damage that is really going to occur even if you take it off the scale!
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Quoting NoVaForecaster:


If it doesn't restrengthen some I am fully prepared to eat some crow. Irene still has some surprises in store for us, IMO.


I agree..These storms are known for strengthening right before landfall....Ike did.
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Quoting Patrap:


Pat you read my mind.
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dry air spiraling intrusion could be creating downdrafts on one side and updrafts with the convection barreling into it from se to nw near the center.

Quoting RitaEvac:
May be strengthening again, latest cold cloud tops near the CDO is getting more noticeable on loops. This maybe her last hoorah before plowing into NC, then up the coast. Don't be relaxed since she's only 100mph now, don't be shocked to see her get back to 115mph
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Quoting Patrap:
Power still out at Folly?


it's back...Thomas and the rig are approaching the eastern NC shore...gonna meet up with some Team Rubicon folks...we're gonna make a nice impact...also working on flying some stuff into the Bahamas tomorrow....
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161:

GFS has been predicting that low for several days now. Might or might not get absorbed into Irene.
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Quoting vortextrance:
NOAA jet is finding 949 mb's.


She is looking better on satellite too...
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pretty impressive that it at least dropped tho. it does look better than what it did a few hours ago.
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Quoting TropicalAnalystwx13:


Eh, not concerned with it. It dropped all day yesterday, and the winds went down. I'll start worrying when the winds being found get higher.


I agree, I was just pointing it out as the pressure had been falling pretty quickly.
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Quoting NoVaForecaster:


Appears to be shielding it from the core pretty well right now.



Thanks Nova
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Oh and btw, to everyone who thinks that because Irene is a Category 2 it can't cause damage. Irene is like Ike, a massive Category 2. That whips up a lot of surge.. know what Ike did to Galveston? I'll post a few picks.. remember this is 'only' a Category 2.




Also, I would like to point out that I have been in a large Category 2 hurricane, Isabel. Pretty bad damage, even in inland VA.
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Irene has certainly jogged eastward (NE) over the past few hours.
Link
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Quoting CybrTeddy:


As you should have noticed during Irene, nothing is a guarantee with models.. particularly 240 hours out.


Yup...according to the models, this should've been in the Gulf of Mexico.
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Link

This radar image tells all. You can see the inner eyewall trying to reform. The band that was trying to become an outer eyewall. The dry air that has split Irenes outerbands from her inner ones. Honestly I'd have probably kept her at a 95-105mph landfall just because every model shows a drop in their pressure fields and the gfdl and hwrf both showed as of earlier today her gaining a little strength back.
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May be strengthening again, latest cold cloud tops near the CDO is getting more noticeable on loops. This maybe her last hoorah before plowing into NC, then up the coast. Don't be relaxed since she's only 100mph now, don't be shocked to see her get back to 115mph

Cold cloud tops showing on RGB loop, she's getting ready for another hoorah
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Quoting NoVaForecaster:


Appears to be shielding it from the core pretty well right now.



Irene is mad that the dry air tried to ruin her party. But she doesn't have much time left to get fully dressed for arrival.
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NOAA jet is finding 949 mb's.
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Quoting oracle28:
IRENE COULD WEAKEN JUST BELOW HURRICANE STRENGTH BEFORE
REACHING SOUTHERN NEW ENGLAND.

This is great news.

Flooding will be the main concern. Wind may be a problem, but not as much as flooding. Learned that the hard way in Puerto Rico.
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Quoting wunderweatherman123:

is it gurranted the next storm recurves because the gfs in literally all of its runs recurves it


As you should have noticed during Irene, nothing is a guarantee with models.. particularly 240 hours out.
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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.