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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Quoting washingtonian115:
I'm with a friend right now that's been storm chasing for a few years now.So I decided to join him.Hey why not.This could be a heck of an experience.


Heck yeah.....I would like to myself....I think :/
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Quoting TStormSC:

I think it is a valid question from an interested recipient of news/weather information that would be more deserving of a response from a weather professional.


Maybe...perhaps I was out of line.
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Quoting MrstormX:
I doubt the storm surge of Irene is as great as Ike, looking at what video feeds there are from the Carolinas the surf is elevated but not horrific. I remember Ike, the storm surge was crashing away before the first rain band even hit the Gulf Coast (Geraldo Rivera fell, and I was like lol).

Now I'm not saying Irene isn't going to have some strong surge, but I also don't think it has the storm surge of a category 4 hurricane as I have heard on this blog throughout the day. Lets hope my thoughts are correct.


Some of the webcams don't show it good...According to the news, a lot of roads near the beach are flooded because the water has come past the sand, up the dunes, and onto the roads...Not good for the houses there.
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I doubt the storm surge of Irene is as great as Ike, looking at what video feeds there are from the Carolinas the surf is elevated but not horrific. I remember Ike, the storm surge was crashing away before the first rain band even hit the Gulf Coast (Geraldo Rivera fell, and I was like lol).

Now I'm not saying Irene isn't going to have some strong surge, but I also don't think it has the storm surge of a category 4 hurricane as I have heard on this blog throughout the day. Lets hope my thoughts are correct.
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346. bwi
First light rain showers associated with Irene now. Warm rain, fine drops. Washington DC area. Pretty big system.
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Cantore was just talking to Dr. Sullivan (live) from the NOAA P3 aircraft. Dr Sullivan mentioned how Irene's eye was disorganized.

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Quoting wunderweatherman123:

la nina AGAIN this winter 0__0 wow


Yup - big bummer for those of us in the PNW.
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Quoting Thunderpig75:


I stopped reading at the first sentence.

I think it is a valid question from an interested recipient of news/weather information that would be more deserving of a response from a weather professional.
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Quoting EYEStoSEA:


Are you and the storm chaser friend out chasing yet ??
I'm with a friend right now that's been storm chasing for a few years now.So I decided to join him.Hey why not.This could be a heck of an experience.
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More 50 mph gusts...
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Looks like Irene may try to intensify, appears where the dry air was convection is coming back a little? She is a strange storm but I would not take her lightly. This storm reminds me of Ike which I rode out in Pearland Tx and was in the western eyewall all night.
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I think Hurricane Irene if she continues to weaken will be like hurricane Alex in the Outer Banks back in 04.With an 85mph.Who knows Irene could be stronger.BTW the GFS developes another storm in 3 days with another one behind it I think.
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Hurricane Irene has turned northeast?
Look at the entire circulation. It abruptly shifts northeast.
http://www.ssd.noaa.gov/goes/flt/t2/flash-wv.html
If this continues that is great news! We need another hour or so to determine a definite change in course and not just a temporary jog/wobble in direction.
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la nina AGAIN this winter 0__0 wow
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Here in Plymouth county Mass. I expect to see wind gusts but no sustained winds. Glad she weakened. But I believe that nobody in Mass will ever believe a forecasted Hurricane except people on Cape Cod. I thought this was going to be my chance to see sustained hurricane winds. Two straight storms , Earl last year, that don't live up to the hype. I will have to be laughed at again in work for saying that this is the one. One day it will happen and it might be the next one.
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Quoting washingtonian115:
I just got updated by my family up there in D.C.They aren't taking the storm seriously any more since it has weaken.There for when it gets to the D.C region Irene will likley produce no higher than 40mph winds.That's what we can get in the winter from Nor'easters.


Are you and the storm chaser friend out chasing yet ??
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Quoting presslord:


Can you take a call?
Finally, yes.
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So my uncle is driving to his beach house in N.C.from Pittsburgh tonight and my family keeps telling him it's a really stupid idea but he keeps saying It's my vacation this week. I know it's somewhere on the coast on the N.C. and S.C. border.
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Damage estimated from Irene have already exceeded $1 billion.

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some damage already in wilmington..courtesy of star news

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Wilmington NC Wind NE 30 gust to 47

Storm will be below cat 1 by time it gets to Jersey. Media really blowing it on this one
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Storms always get overstated. They're not going to have another Andrew or another mini-Andrew.

It's probably a 1 now, but who cares. This is more of a rain/surge storm anyway. And in the scheme of things, what's the difference between a 90MPH 1 and a 100MPH 2. Both still suck.
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326. 996tt
Quoting victoriahurricane:


Let me remind you Ike was a Category 2 and Irene hase the IKE (not the storm) of a Category 3 hurricane. Oh yeah and Ike was one of the costliest to hit the U.S. ever. Don't be so blase when it comes to this storm. They've already reported flooding in Georgia and North Caroline and the storm isn't supposed to get there for another 18 hours or so. The East is going to be in for a wild ride even if it's "only" a Category 1 storm.


Seems like people would be greatful its not a cat 3 or higher. Low lying areas will get flooded no doubt. That's horrible. At least everything won't get decimated. Much better situation than previously thought.
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Is there a way to overlay SSTs on the Wundermap? I'd like to see the Sea Surface Temps along the East Coast.
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Just remembered something: when the warmest waters underneath a hurricane that provide fuel for intensification are located in the outer flanks, such as when the Gulf Stream is located to Irene's west and north, the storm will...weaken. Since the outer bands are more likely to develop via influence of warmer SSTs, some storms will thus expand, and unravel as the storm's energy gets pushed towards its outer layers.

Currently, Irene looks like the storm is "shedding". The outer bands are now making landfall, yet this means the inner CDO could have a chance to re-strengthen, provided this convection protects Irene from dry air. She's definitely a strange girl.
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Quoting PureScience:
I am just a high school drop out but I can't help but wonder why we even spend a dime sending Hurricane Hunters into storms to get precise measurements when the guys and gals with the degrees resort to assumptions and guesses of the storms intensity when they don't get readings to support their hype.


"Assuming the aircraft missed sampling the strongest winds of the hurricane, it's a good guess that Irene is a mid-strength Category 2 hurricane with 100 mph winds."
Dr. Jeff Masters weather blog 3:14 pm GMT 08/26/2011

A couple of quotes from others:

"Although not shown in the official
forecast...Irene could weaken just below hurricane strength before
reaching southern New England."
forecaster Brown/cangialosi


Hurricane Irene Discussion Number 23
Statement as of 11:00 PM EDT on August 25, 2011
" two hurricane hunter aircraft...one Air Force and one NOAA...are
again tonight supplying very valuable meteorological data to the
National Hurricane Center. Both planes indicate that the central
pressure is gradually falling and is now near 942 mb...but the
winds have not increased yet. The initial intensity is kept at 100
knots at this time."
forecaster Avila

The two hurricane Hunter reports preceding this forcast found maximum surface winds of 70MPH and 90MPH...Heck why not round it up to a nice even 100kts. After all 115mph Cat 3 storm is much scarier than a strong TS or a CAT 1 hurricane. I guess it is fine to ignore the data and fan the flames of fear in the public to keep the herd moving.




http://www.flickr.com/photos/66821844@N03/6083932 320/in/photostream/

http://www.flickr.com/photos/66821844@N03/6083929 056/in/photostream/Link


I stopped reading at the first sentence.
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I'm sitting here on the blog tonight thinking that this must be the largest collection of hurricane watchers in history who are like film critics knowing for once that they are not a target of a storm.
I know there are many of you in the path but all those people who don't know whats coming should listen to you veterans compulsory.
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guys if you are going wave watching on the beach un les they have it close plzs where a life jacket so that way if a wave comes up and take you out too sea the life jacket will keep you a float in tell help comes



life jacket can save your life plzs ues it and ware it and stay safe at the same time
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I just got updated by my family up there in D.C.They aren't taking the storm seriously any more since it has weaken.There for when it gets to the D.C region Irene will likley produce no higher than 40mph winds.That's what we can get in the winter from Nor'easters.
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Quoting JLPR2:


Shear. It just wasn't meant to be. xD

lol
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Wilmington NC NE 30 gust to 47. Lost power for 2 hours just got it back.
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Quoting charlottefl:


You're really gonna sleep tonight ?


I'm gonna try :P
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Quoting TropicalAnalystwx13:
Power flickers...

Dear Hurricane Irene,

Please keep the power on until we are asleep.

Thanks,
TropicalAnalystwx13



You're really gonna sleep tonight ?
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Sorry for the caps lock guys and thanks to all who helped me out, I appreciate it :)
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Quoting yoboi:
is something forming south of cuba?



There was actually an untasked recon that released a dropsonde in the area this morning. Appears to be somewhat of a low level circulation just north of the DR. coast however, struggling in the outflow of Irene. Just FYI, and to justify your thoughts.

Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KNHC)
Transmitted: 26th day of the month at 16:18Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Mission: Non-Tasked Mission, possibly not tropical (flight in the North Atlantic basin)
Mission Identifier: 110826145138302 (2 digit year/2 digit month/2 digit day/6 digit mission start time/Last 3 digits of aircraft tail number)
Date Mission Started: August 26th in '11
Time Mission Started: 14:51:38Z
Observation Number: 05

Part A...

Date: Near the closest hour of 16Z on the 26th day of the month
Highest Mandatory Level For Which Wind Was Reported: 400mb
Coordinates: 19.5N 68.4W (View map)
Location: 120 miles (194 km) to the NE (54°) from Santo Domingo, Dominican Republic.
Marsden Square: 043 (About)


Level Wind Direction Wind Speed
1016mb (Surface) 125° (from the SE) 13 knots (15 mph)
984mb 130° (from the SE) 13 knots (15 mph)
956mb 155° (from the SSE) 19 knots (22 mph)
891mb 140° (from the SE) 13 knots (15 mph)
850mb 150° (from the SSE) 12 knots (14 mph)
558mb 40° (from the NE) 3 knots (3 mph)
496mb 45° (from the NE) 10 knots (12 mph)
489mb 25° (from the NNE) 11 knots (13 mph)
442mb 345° (from the NNW) 16 knots (18 mph)
393mb 350° (from the N) 18 knots (21 mph)
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Power flickers...

Dear Hurricane Irene,

Please keep the power on until we are asleep.

Thanks,
TropicalAnalystwx13

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Hope everyone has their supples if you are riding out the storm,good luck and stay safe....
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Quoting Tazmanian:
guys if you are going wave watching on the beach un les they have it close plzs where a life jacket so that way if a wave comes up and take you at too sea the life jacket will keep you a float in tell help comes



life jacket can save your life plzs ues it and ware it and stay safe and the same time


Great info, Taz :)
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307. JLPR2
Quoting WeatherNerdPR:

What in the world happened to it?!


Shear. It just wasn't meant to be. xD
Member Since: September 4, 2007 Posts: 7 Comments: 8459
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Quoting Grothar:
Doesn't look that weak to me. Looks stronger on each frame



Everything looks amazing the satellite lol. BBL.
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Was wondering why the postings on the last blog were so slow. Reposting with landfall time correction.

30.0n77.3w has been re-evaluated&altered for H.Irene's_6pmGMT_ATCF
30.0n77.4w, 31.2n77.5w are now the most recent positions
Starting 25August_6pmGMT and ending 26August_6pmGMT

The 4 shorter line-segments represent HurricaneIrene's path
and the northernmost line-segment is the straightline projection.

Using straightline projection of the travel-speed&heading derived from the ATCF coordinates spanning the 6hours between 12pmGMT then 6pmGMT :
H.Irene's travel-speed was 13.8mph(23k/h) on a heading of 355.9degrees(N)
H.Irene was headed toward passage over Ogden,NorthCarolina ~11hours from now
(ILM is WilmingtonInternationalAirport)

Copy&paste 26.5n77.2w-27.7n77.3w, 27.7n77.3w-28.8n77.3w, 28.8n77.3w-30.0n77.4w, 30.0n77.4w-31.2n77.5w, ilm, 30.0n77.4w-34.246n77.768w into the GreatCircleMapper for more info

The previous mapping (for 26August_12pmGMT)
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Quoting Grothar:


Stop being so pixy! There were 2 there a few minutes ago. Looks like it wants to come back a little. Looks a litle better than 1/2 hour ago.



Dry air slot closing off slightly.
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guys if you are going wave watching on the beach un les they have it close plzs where a life jacket so that way if a wave comes up and take you at too sea the life jacket will keep you a float in tell help comes



life jacket can save your life plzs ues it and ware it and stay safe at the same time
Member Since: Posts: Comments:

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.