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 53rdWeatherRECON:


Look at the SST maps.

Look at her projected path.

The puffs of convection come from Hot SST's.

Her surge and windfield is plowing the fresh hot Gulf Stream into every bay up the east coast.

That water is almost as warm as the Gulf itself until you pass the Outer Banks.

The models are seeing this.
100% agreed!
Member Since: June 24, 2007 Posts: 0 Comments: 1477
Gonzo (Gulfstream IV) is picking up intermittent dry air in the SE quadrant. Just how far apart do temp and dew point need to be to dry enough to have a significant effect? Does it need to be consistent through altitude?

Thanks.

Looks like they are running a counter clockwise pattern. I would imagine that saves quite a bit of fuel ;-).
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1122. Levi32
Quoting 53rdWeatherRECON:


Look at the SST maps.

Look at her projected path.

The puffs of convection come from Hot SST's.

Her surge and windfield is plowing the fresh hot Gulf Stream into every bay up the east coast.

That water is almost as warm as the Gulf itself until you pass the Outer Banks.

The models are seeing this.


Right, the models are seeing the water. It's hard to tighten up the core of a dried-out hurricane as large as this though, and the Gulf Stream is very thin. The models may be responding too quickly to it, but we will see. I've had my forecast for a low-end Cat 3 at landfall for a while now, and I'll stick to it based on what we're seeing today.
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Quoting Motoko:


Could this be the first winner of the Darwin Award?


Don't forget the poor soul in PR who was driving on a flooded road. She should be in the nomination pool.
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If you ARE living in a low-lying area near the coast or river...and plan to evacuate, please don't leave without;

1) Turn OFF your main electrical breaker. Before electricity goes off for good, it often surges off/on first in hurricane winds. You don't need the extra damage that surging electricity can cause.

2) Turn OFF your main gas valve to the house. If something happens to your home... you don't want THAT danger to add to the problem. It only takes a few seconds to turn back on afterward.

3) Turn OFF the main water valve to your home. Again... you can always turn it on again later. If anything happens (tree falling on home, etc...) you don't want an interior water leak to add to the flooding problems.

If you watched the footage from Galveston pre-Ike... you likely saw several house fires happen when the winds kicked up. Same thing pre-Rita. The fire department can't respond if the winds are above 35-40 mph. If tropical storm force winds have arrived, fire & police will NOT respond to calls. You don't want YOUR house to be a potential risk. It only takes a few seconds, but may save your home from catastrophic damage while you're gone.
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1117. HCW

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ok...out for a bit...gonna try to brave the streets b4 the next feeder band...
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My guess is that Irene will be borderline cat1/2 at landfall in NC, rain will be a huge issue up through Maine though.
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10-15 MPH sustained, 20-25 MPH frequent gusts, 30-35 MPH infrequent gusts.
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Quoting TexasGulf:
If you live in a well-built home or building a bit inland or at a higher elevation (20-ft above sea level or more)... think about calling your friend's family that lives near the beach or in a low-lying area near the river. Invite them to spend Saturday night and Sunday with YOUR family.

Some people won't evacuate simply because they can't afford it. Others just don't want to inconvenience anybody. Still others aren't aware that they have anyplace else to go. In some of those cases, people are too proud or embarrassed to ask for help.

Your phone call and offer might just save their lives. It may be a BIG relief to them. If you have a fenced back yard... invite them to bring their dog. Cats or birds will likely not be that big of a deal for 1 day. Some people won't evac without their pets. Tell them to bring their cars, boat or RV. Some people won't leave without "stuff".

If you are going to call... do it today. Give people a chance to pack and leave. Give them a safe place to go. One day won't hurt... and the chance to evac safely may be the biggest gift you ever gave them.


Great post
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Quoting Levi32:


We'll probably know in 12 hours whether it's going to tighten up or not. I'm still keeping it at 115mph at landfall. We'll see how it goes. These finer details in strengthening/weakening trends are difficult to forecast.


Look at the SST maps.

Look at her projected path.

The puffs of convection come from Hot SST's.

Her surge and windfield is plowing the fresh hot Gulf Stream into every bay up the east coast.

That water is almost as warm as the Gulf itself until you pass the Outer Banks.

The models are seeing this.
Member Since: August 5, 2005 Posts: 2 Comments: 80
Quoting Bluestorm5:
gust of 35-40 just hit my house, but went back to 10-20 mph now.



Where are you located?
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Quoting Neapolitan:
Something tells me that many (most? all?) of those accusing various authorities of "fear-mongering" and "over-hyping" for taking precautions to ensure that damage to life and property is minimized are probably the exact same people who were first online after Katrina or the Japanese tsunami to accuse authorities of malfeasance for failing to do enough to warn and protect their citizens.

Armchair quarterbacking is a famous American sport, but it sure does get tedious to listen to...
Agreed about the Armchair quarterbacking but not so much about your first comment.
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Quoting Bluestorm5:
Dr. Masters, NHC, and Weather Channel are all saying the highest tide of the month. Is it the lowest or the highest tide of the month, anyone?
Lowest low and highest high I believe. As with many things timing is critical.
Member Since: September 9, 2007 Posts: 36 Comments: 4687
Can anyone explain to me the latest steering forecast? I can't seem to find it. Going mobile here...:(
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Anyone have a link that lists evacuation orders?
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I think Irene is just maintaining and preserving her strength at best. This storm seems to still be expanding itself slightly which is amazing given how big it is already. I don't her to strengthen more than 5-10 MPH and I don't think it will make a big difference if she does so. The fact is she has Cat 3 level air pressure and this should be a sign enough that the winds on this storm is not a good enough representative of how powerful it is.
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1100. Levi32
Quoting BLee2333:
Don't underestimate this storm. She may look ragged and weaker at the moment, but she's still packing the kinetic energy of a major CAT3.



As she should with a 951mb pressure. That's why she's so dangerous. The storm surge will be typical of a Cat 3 even if she's a 2.
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Anyone have a link that lists evacuation orders?
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Must say great job so far with the predicted track.
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1097. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 174 Comments: 54473
Quoting seafarer459:


Good my friend. And you?



am doing vary vary well
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1095. Motoko
Quoting tiggeriffic:


kite boarder near sullivan's island was spotted bout mile out...then that bad feeder band hit...last i heard they were still looking for him


Could this be the first winner of the Darwin Award?
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Flooding could become a huge issue with Irene, as the wind threat diminishes.
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1093. oakland
Quoting NoVaForecaster:
Why have i had to poof like 20 people today? Don't people have better things to do than spam a tropical weather blog when a disaster is occurring?


Sadly no.......
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gust of 35-40 just hit my house, but went back to 10-20 mph now.
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1090. dewfree
funny i see most of you when im not posting im watching i have seen most of you post things that were not of topic , i see that troll stuff alot too . care that you are not what you may be calling others lol have a good one and like i said i will return to see the accuracy of what i said ,if you have any problems with that ,please reframe from letting us know . and you are right this is a tropical weather blog untill something better comes along lol . i have seen it all on here ,especially when there isnt any activity in the tropics ,
God given gifts have nothing to do with the ability of man to train hiself in his schools to the facts of propaganda. have a nice day like i said im gone
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Don't underestimate this storm. She may look ragged and weaker at the moment, but she's still packing the kinetic energy of a major CAT3.

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Quoting PrivateIdaho:
Charleston Air Force Base
Lat: 32.91 Lon: -80.03 Elev: 59
Last Update on Aug 26, 2:56 pm EDT


Light Rain

75 �F
(24 �C) Humidity: 96 %
Wind Speed: N 20 G 25 MPH
Barometer: 29.66" (1004.2 mb)
Dewpoint: 74 �F (23 �C)
Visibility: 8.00 mi.
More Local Wx: 3 Day History:


Not to bad inland a little bit.


im between the 2...Press directly on the beach...
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1086. oakland
Quoting Tazmanian:



i no you guys no that am the real me but do the admins no


Yes Taz they know. Don't worry about it.
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Quoting Levi32:


Probably because it's been aimed at your house :P

But yes, it has been an interesting storm.


lol.
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Quoting Tazmanian:



hi how are you


Good my friend. And you?
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1083. HarryMc
Quoting Levi32:


We'll probably know in 12 hours whether it's going to tighten up or not. I'm still keeping it at 115mph at landfall. We'll see how it goes. These finer details in strengthening/weakening trends are difficult to forecast.


I'm agreeing with you Levi. Structure is there less well-defined eye. Nothing in its path for it to stumble on at this point.
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1082. Thaale
Does anybody know what Irene's IKE is, as compared to say those of Katrina and Ike as they approached landfall? I don't know what site supplies IKE stats. TIA.
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imposter taz tisk tsik such a sad little person peoples lives are in danger and all you do is come on to a site of profecionls and mess you about i pity you sir >>>> IN OTHER NEWS take a look at latest vis pass of irene shes dead
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Here is a local news station for you LeviLink streaming available.
Member Since: June 24, 2007 Posts: 0 Comments: 1477

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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.