Irene's eyewall collapses; further intensification unlikely

By: Dr. Jeff Masters , 3:14 PM GMT on August 26, 2011

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Satellite data and measurements from the Hurricane Hunters show that Irene is weakening. A 9:21 am EDT center fix by an Air Force Reserve aircraft found that Irene's eyewall had collapsed, and the central pressure had risen to 946 mb from a low of 942 mb this morning. The highest winds measured at their flight level of 10,000 feet were 125 mph, which would normally support classifying Irene as a Category 3 hurricane with 115 mph winds. However, these winds were not mixing down to the surface in the way we typically see with hurricanes, and the strongest surface winds seen by the aircraft with their SFMR instrument were just 90 mph in the storm's northeast eyewall. 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. 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 wind shear of 10 - 20 knots due to upper-level winds out of the southwest. 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 Wlimington, North Carolina, shows that the outermost spiral bands from Irene are now beginning to come ashore along the South Carolina/North Carolina border. Winds at buoy 41004 100 miles offshore from Charleston, SC increased to 36 mph as of 10 am, with significant wave heights of 18 feet.


Figure 1. Distribution of Irene's wind field at 9:30 am 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 and storm surge potential for Irene
With its eyewall collapsed and just 24 more hours over water before landfall, it is unlikely Irene will 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 Category 2 hurricane at landfall in North Carolina on Saturday, and a rapidly weakening Category 1 hurricane at its second landfall in New England on Sunday. 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 9:30am EDT this morning, a wind analysis from NOAA/HRD (Figure 1) indicated that the potential storm surge damage from Irene rated a 5.1 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 gradually decline as Irene moves northwards and weakens, we can still expect a storm surge one full Saffir-Simpson Category higher than Irene's winds. 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. A surge rivaling that experienced during Hurricane Isabel in 2003 is likely in northern NC, southern Maryland, and up Chesapeake Bay on Saturday night. Coastal New England from New York City to Massachusetts may also see storm surges characteristic of a Category 1 hurricane during Sunday morning's high tide, even if Irene has weakened to a tropical storm. I continue to give a 20% chance that a storm surge high enough to over-top the Manhattan flood walls and swamp the New York City subway system will occur on Sunday.

Wind damage
I don't think Irene is going to do a lot of wind damage to the mid-Atlantic states, since the eye of the storm will be just offshore, and the I-95 corridor from Virginia to New Jersey will be on the weak (left) side of the hurricane. The current wind distribution of Irene (Figure 1) shows almost all of the hurricane's winds are on the right side of the storm, and by the time the storm reaches Virginia, there will be likely be no hurricane-force winds on the left side of Irene. Sustained winds should stay below 74 mph (hurricane force), and wind damage will be similar to that wrought be some of the strongest Nor'easters of the past 20 years, from Virginia northwards to New York City. Since Irene will be steadily weakening as it approaches its second landfall on Long Island, I give a 50% chance that no mainland U.S. surface station in New England will record sustained hurricane-force winds. I do think it likely that one or more of the offshore islands--Block Island, Nantucket, and Marthas Vinyard--will get Category 1 hurricane winds. Though the wind damage to buildings will be similar to what the Northeast has seen during some of the more severe nor'easters of the past 20 years, tree damage will be much worse. The trees are in full leaf during hurricane season, and catch the wind much more readily than during the winter. Tree damage will very heavy, and we can expect trees in regions with saturated soils will fall over in high winds onto power lines. Irene is likely to cause one of the top-five most widespread power outages in American history from a storm. The record power outage from a Northeast storm was probably the ten million people that lost power during the great Blizzard of 1993. I don't think Irene's power outages will be quite that extensive, but several million people will likely lose power.

Irene likely to bring destructive fresh water flooding
In addition to storm surge, flash flooding and river flooding from Irene's torrential rains are the main threats. The hurricane is expected to bring rains in excess of 8" to a 100-mile-wide 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. New Jersey has had its 6th wettest August on record, with most of that rain falling in the past two weeks. Expect major river flooding throughout New Jersey the Delmarva Peninsula, and regions near New York City, as Irene's rains run off the saturated soils directly into the rivers. 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. I don't think flooding from heavy rains will be a huge concern in North Carolina, which is under moderate to severe drought. Irene's rains are likely to do some good in Southeast Virginia, where a fire triggered by lightning from a thunderstorm on August 4 sparked a fire in the Dismal Swamp that is burning out of control. 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 Wednesday August 31, as issued by NOAA/HPC.

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 there, and I will be available if my schedule permits. Listeners can email in or call in questions. The email address to ask questions is broadcast@wunderground.com.

Portlight mobilizes for Irene
The Bahamas have been hit hard by Irene, and unfortunately, it appears that the Northeast U.S. may have its share of hurricane victims before Irene finally dissipates. My favorite disaster relief charity, Portlight.org, is mobilizing to help, and has sent out their relief trailer and crew to North Carolina. Check out this blog to see what they're up to; donations are always needed.

Jeff Masters

Hurricane Irene's Wrath ! (MikeTheiss)
A shot of the Palm Trees at Nassau, Bahamas being thrashed by high winds during Irene's closest approach !
Hurricane Irene's Wrath !
Aftremath of Hurricane Irene in Nassau, Bahamas (ktbahamas)
Utility pole with street light snapped in half by Irene's winds on a busy street in New Providence.
Aftremath of Hurricane Irene in Nassau, Bahamas
Irene Response (presslord)
Portlight deploying to North Carolina
Irene Response

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Quoting CapnK:
First rainband in Georgetown, SC this AM.




Full size image (800pix wide) at my WU blog.


yeah...we were hit with some in charleston...im in town so didn't get any good pics like that...but saw the black flying at me when i was outside...it was wicked to say the least...not hitting us head on but the Hugo flashbacks were well...yeah...
Member Since: September 16, 2007 Posts: 0 Comments: 3650


~90knots +- 5 from radar radial velocity

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Quoting CajunCrawfishhunter:



FOOL


Keep doom casting if that makes you feel better.
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Quoting Tazmanian4:
Do i this say poof to you as well?


you may if you want but he is still a fool if he thinks that becuase the media prepares for the worst to save lives is wrong then so be it. Id rather be worried and alive that sitting back in my lazy chair and die
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Quoting Caladesian:
Hurricane hints:
If a storm is fast moving, placing duct tape around the doors sometimes can prevent seepage from the storm surge. (Worked with Hurricane Andrew in Miami, but only if storm surge persists for a short period of time and is not very deep.)

Even one inch of seawater in your home can destroy the carpet, especially if power outages prevent drying afterwards, so it might be worth the effort.

Also, placing furniture on blocks or trestles may help if the storm surge at your home is not too high. Elevate everything possible off the floor and onto tables or anything higher. If the storm surge at your house is 15 feet, nothing will help, but more people will have the situation of it being only a few feet or even inches.

Consider double bagging art or photographs with heavy garbage bags. When the window of my grandmother's home blew out, all surfaces were covered with a green slime of rain and shredded leaves. The mold destroyed a lot of our family photographs and artwork.


Great hints -- I regularly take down and bag some art work my mother did before she died, and most of our pictures are in sealed plastic containers. That way don't even have to think about those.
Member Since: August 13, 2007 Posts: 10 Comments: 4141
She's about to run into some 30 degree water from the Gulf Stream. It'll be interesting to see if we get a little flair up out of her.
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wb levi
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819. AVL
Just a lil info from the mountains of NC. Dark here but no real rain to speak of...I did pass the dudes from Storm Cahsers this am headed east on 40...The guys with the maroon armored vehicle...I think the guys name is Shawn Casey...Nyways, just thought I would share...
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Quoting Levi32:
Good afternoon all. I'm back in Fairbanks.

Irene has risen a few more millibars in pressure and convection in the core is weak. Outflow is improving slightly in the SW quad, but dry air will remain in her circulation no matter what due to her size. We are hoping for continued weakening right up until landfall, but as noted in the video, the GFDL and HWRF, as well as all of the intensity models really, show a weakening Irene for the first 12 hours today, and then strengthening between the 12 and 24 hour period, right at landfall. The global models showing a deepening pressure field agree with this, so we may see Irene make a small comeback right at landfall, perhaps trying to get those winds to match her low pressure, which supports a Cat 3 hurricane.



FINALLY! SOMEBODY WITH COMMON SENSE!!!
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Quoting Bluestorm5:
Johnston County is under High Wind Warning. Wake County is NOT.


Wake and Durham are now under a High Wind Advisory, which may be upgraded to a High Wind Warning.
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Good afternoon all. I'm back in Fairbanks.

Irene has risen a few more millibars in pressure and convection in the core is weak. Outflow is improving slightly in the SW quad, but dry air will remain in her circulation no matter what due to her size. We are hoping for continued weakening right up until landfall, but as noted in my blog this morning, the GFDL and HWRF, as well as all of the intensity models really, show a weakening Irene for the first 12 hours today, and then strengthening between the 12 and 24 hour period, right at landfall. The global models showing a deepening pressure field agree with this, so we may see Irene make a small comeback right at landfall, perhaps trying to get those winds to match her low pressure, which supports a Cat 3 hurricane.

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Quoting SeniorPoppy:
So much for the monster entering the northeast. The scare tactics by the media has been nothing short of brilliant. There still will be power outages and trees snapping etc, stupid people going outside during the storm, probably some flooding, but nothing depicted by twc and media.



FOOL
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Quoting stillwaiting:
,you live in a fantacy world,and it looks like irene's moving north


I'm living in a fantasy for saying that Bush and Reagan were on working vacations at their ranches, that is my historical interpretation so deal with it. And yes...Irene is moving pretty much due North.
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808. CapnK
First rainband in Georgetown, SC this AM.




Full size image (800pix wide) at my WU blog.
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not sure where this is but the beach view slowly deteriorates. This will get worse and go on for hours










Streaming Live by Ustream
Member Since: September 22, 2005 Posts: 11 Comments: 2032
so Irene has thrown up and has a case of the flu.Looks like she is still heading for the area i told you day before yesterday at 2:pm in the afternoon . between Mertle and kitty hawk
I think it is too late to replace eyewall to be any more then cat 1 when she meets land .
That is bad enough don;t you guys think . still has plenty of moiture to work with and can still create a mess.
I like the duct tape thing;it is very southern ;of corse about 60%of the things we have in this country is southern idea's. one of them most people could not live without and that is air conditioning ,you can thank a doc from florida for that one .you will find duct tape anywhere from nascar racer to now the door of your home to prevent storm surge .improvise and overcome uurah!!
dew
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Quoting reedzone:


People just don't understand how dangerous this storm is..
The Dr. posted an extensive blog yesterday speaking to how disastrous this could be. Plus, the blog in general has been realistic in recognizing this as a potential historic calamity. But, we also see what's going on today, and it's possible things, while very bad, may not be a super-duper apocalypse. But, it could. We'll see what happens. We haven't been in denial of the potential or the weakening.
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Irene:

"Rumors of my death have been greatly exaggerated!"

Just ask this brave little Buoy South of Wilmington:

Buoy 41013

In addition to the waves, the wind is now sustained at near 40 knots with gusts near 50, and best I can tell, the center's still over 100 miles away.
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Quoting MrstormX:


Well the Bush and Reagan vacationed at their private ranches, which were in effect secondary White Houses. So basically working vacations.


Any POTUS is never really on vacation, no matter where he or she may be.
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Quoting Tazmanian4:
Guys plz sttop this saying this storm is weakening al so we may see some intensication later


It'd be nice if you wouldn't impersonate people..
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Ok for the people who are coming in here for ACCURATE info on dangerous Hurricane Irene, here's what YOU need to know :)

1. Category 2/3 landfall or brush in North Carolina
2. Hurricane landfall on Long Island
3. Pressure equivalent to a Category 4 storm so the surge and intensity of the storm is to be treated as a Category 3/4 storm
4. Big comparison to Hurricane Ike in 2008 by it's large wind field.. You all know how bad Ike was, don't be fooling around with Irene just because she weakened a little bit.
5. Irene should be moving north into some warmer waters in which is why models re-intensiy her a bit more.
6. If you need more ACCURATE info, see ur local authorities and really good bloggers like Levi, Hurricane23, Drakeon, Patrap, and some others on here.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Storm is looking Awful.

Big bust potential at this point.

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So much for the monster entering the northeast. The scare tactics by the media has been nothing short of brilliant. There still will be power outages and trees snapping etc, stupid people going outside during the storm, probably some flooding, but nothing depicted by twc and media.
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Quoting DavidHOUTX:


You have a valid point but the problem that the media (especially the NWS) faces with "up-playing" a storm before landfall is that if the storm arrives and it turns out to be a rain shower at most; the NWS is under the gun. All the people (that are clueless) blame the NWS/media for the "headache" they caused them.

I agree its far better safe than sorry but its a double edged sword for the NWS/media.


Remember: "You have to be alive to be inconvenienced"
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09L/MH/I/C2
RI FLAG (off)
RD FLAG (flag)
MARK
32.25n/76.98w





ALWAYS FOLLOW NHC/TPC FORECASTS FOR ALL WARNINGS REGARDING THIS STORM
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The dry slot appears to be filling in on radar.
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Quoting MrstormX:


Well the Bush and Reagan vacationed at their private ranches, which were in effect secondary White Houses. So basically working vacations.
,you live in a fantacy world,and it looks like irene's moving north
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Yeah, go ahead and keep downing the storm so people who are looking for information will think it is not a threat and weakening. Just keep doing that and give them a false sense of security.

You're doing a good job.

Sarcasm Flag: ON
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Quoting FLdewey:
The garden state parkway is going contra-flow tonight.

Now that I got to see.

*fist pump*
Not true. Parkway will be closed to Southbound traffic South of Exit 98 only (mid-state, crossing with I-195) starting at 8 pm tonight, but I haven't heard of any contra-flow. Just no southbound traffic. North of Exit 98, the parkway will be open both directions.
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off to work, good luck and ill be back tonight all!
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Quoting NoVaForecaster:


Just because it has temporarily weakened does NOT mean that it is done strengthening permanently. Conditions are still favorable for strengthening, although the window is closing. Read Dr. M's post. Even a moderate TS will have at least cat 1 surge just due to the massive size of this thing.

my thoughts exactly! thanks nova
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Quoting DavidHOUTX:


You have a valid point but the problem that the media (especially the NWS) faces with "up-playing" a storm before landfall is that if the storm arrives and it turns out to be a rain shower at most; the NWS is under the gun. All the people (that are clueless) blame the NWS/media for the "headache" they caused them.

I agree its far better safe than sorry but its a double edged sword for the NWS/media.


Especially in this country. People will always have something to complain about one way or the other. It's the nature of our society to require negativity in order to feel satisfied.

-facepalm-
Member Since: November 17, 2010 Posts: 11 Comments: 527
Quoting SeniorPoppy:


A tropical storm.

yes lol, good catch. its a hurricane not a nor'easter lol.
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Quoting ConnecticutWXGuy:


apparently you think they should say NNW or NNE if the direction is even a fraction of a degree off of complete due north. But there is a guideline as to what direction is what.



Wow, I'm out of here. I now see why a lot of the regulars are no longer here. I state a fact and get mocked for it, what jerk you are. The angle marked NNW on your compass matches up perfectly with the angle Irene took the past 3 hours.
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Quoting MrstormX:


Well the Bush and Reagan vacationed at their private ranches, which were in effect secondary White Houses. So basically working vacations.
Quoting MrstormX:


Well the Bush and Reagan vacationed at their private ranches, which were in effect secondary White Houses. So basically working vacations.


and so is every vehicle whether plane or bus that the pres uses for transportation...and they never leave the pres' location...
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Good bye NYC. Hope to see you again someday.
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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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