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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129. dader
Quoting reedzone:
Dr. Masters is not god, ok? He was just putting out his OPINION on the storm, it's not a fact Irene will rapidly weaken. The storm is not winding down very fast, in fact an eye has popped back out in the latest visible frames and structure has improved. People should NOT let their guard. I have a feeling we will loose ALOT of lives this weekend because you all are letting your guards down. Good luck, seriously :/


My problem with Reed's comments are he puts words in Dr. Master's mouth.

1. Masters did not say that it will weaken rapidly.
2. He did not say it will wind down fast- he said the exact opposite.
3. He talked about the eyewall and said he did not believe it had the time over water to replace it.
4. He never told anyone to let their guard down. Ever- he merely is stating his opinion based on facts.
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flooding going to be what we remember about her in the ne everyone who is capable needs to get out there and catch a good wave good for the soul
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126. 900MB
Quoting reedzone:
Dr. Masters is not god, ok? He was just putting out his OPINION on the storm, it's not a fact Irene will rapidly weaken. The storm is not winding down very fast, in fact an eye has popped back out in the latest visible frames and structure has improved. People should NOT let their guard. I have a feeling we will loose ALOT of lives this weekend because you all are letting your guards down. Good luck, seriously :/


Just saying NYC looks much better at this point. I have my crank radio, tons of food and water, batteries, etc...Outer Banks are a different story, but NYC can handle 75mph.
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Question, is Irene's forward speed too much to maintain hurricane characteristics?
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The lack of any significantly cold cloud tops around the eye (or what's left of the eye) should tell us that Irene is simply maintaining intensity. If we start seeing hot towers, then a strengthening phase may begin. However, time is running short for that to happen.

Member Since: July 15, 2006 Posts: 17 Comments: 10250
Quoting reedzone:
Dr. Masters is not god, ok? He was just putting out his OPINION on the storm, it's not a fact Irene will rapidly weaken. The storm is not winding down very fast, in fact an eye has popped back out in the latest visible frames and structure has improved. People should NOT let their guard. I have a feeling we will loose ALOT of lives this weekend because you all are letting your guards down. Good luck, seriously :/
You seriously need to go away for a while and check your ego at the door while u r at it.
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Quoting Vincent4989:
Alright i'm switching my focus to Nanmadol. Anyone second that?
Nanmadol literally stalled off the coast of Luzon. Any serious damage? Nanmadol still looks like a beast. I think it's veering off to the northeast.
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Dr. Masters is not god, ok? He was just putting out his OPINION on the storm, it's not a fact Irene will rapidly weaken. The storm is not winding down very fast, in fact an eye has popped back out in the latest visible frames and structure has improved. People should NOT let their guard. I have a feeling we will loose ALOT of lives this weekend because you all are letting your guards down. Good luck, seriously :/
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Quoting cloudburst2011:
jim cantore must be really depressed the way he was hyping this storm up last night in new york...
Or maybe he is very happy that a worst case scenario may not occur. Geeeeeeeeeeeeezzzzzzzzzzzzz what a comment.
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Quoting ILwthrfan:


I could very well be wrong, I am no expert, but just looking at the WV and Shortwave I see massive dry air coming in from the west through the south side of her and she's about to wrap it around her east side. I think people in here are starting to think I am troll..maybe I should just keep my mouth shut and go back to lurking.

http://www.ssd.noaa.gov/goes/flt/t2/loop-wv.html


No, you have every right to present an argument based upon the data available. Don't be intimidated by others on here that disagree with you.
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Alright i'm switching my focus to Nanmadol. Anyone second that?
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Quoting reedzone:


NO!


Careful, I think some are just trying to rile you up. Best to ignore, I think most bloggers here are quite sensible not to dismiss Irene. It's not worth your time or effort.
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Quoting sullivanweather:
I know many have been comparing this storm to Ike given the size and the relative low pressure given the sustained winds.

If anyone remembers, Ike gave one last attempt at building an eyewall as it was making landfall so just because Irene looks ragged right now doesn't mean that it can't quickly reorganize.


Correct, when Ike was a few miles from landfall. The eye of this hurricane is still a full day from landfall.
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Quoting atmoaggie:
Umm, seriously?

No-se Jo-way.


I believe the comment by our friend from the 754 was dripping with sarcasm. Trust the models everybody. Reed, Dr. M downgraded the winds inland not the immanency of the destruction that lies ahead from a multitude of factors.
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Quoting oracle28:
I, for one, am glad to read that it's weakening this morning.
It's still a hurricane, a large one too.
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Quoting reedzone:


NO!


People need to still take this storm VERY seriously. She's got a BIG wind field. Her low pressure is also a direct correlation to a massive surge. The wind problem may not be as bad as once thought, but it all depends how the winds in the upper levels transfer down to the surface when she comes ashore.
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At this point, anyone saying "no big deal" should not be deemed a credible person.
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I, for one, am glad to read that it's weakening this morning.
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Quoting ILwthrfan:


I could very well be wrong, I am no expert, but just looking at the WV and Shortwave I see massive dry air coming in from the west through the south side of her and she's about to wrap it around her east side. I think people in here are starting to think I am troll..maybe I should just keep my mouth shut and go back to lurking.


You are correct. The storm is winding down very fast.
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The NHC has always emphasized that intensity forecasts are always their least-skilled forecast. People should certainly not take Irene any less serious as she is still a massive hurricane that's going to do a lot of damage along the beaches and possibly in NYC.
Member Since: July 15, 2006 Posts: 17 Comments: 10250
I think some of you may be over doing her weakening here. Clearly yes her inner core has suffered over the past few hours and collapsed, so yes, maybe the area that will be hit by the exact center will experience less wind damage than expected...but was that ever the worry really with this storm? Due to the size of the storm the wind field is huge, and the storm surge potential is also huge, and considering the fact it is headed into HUGELY populated areas, that is what is so worrying.
Member Since: September 18, 2009 Posts: 0 Comments: 36
Quoting saylo2mylilfren:
She is undergoing an eye wall replacement cycle
Not entirely sure. The eyewall has virtually collapsed, I could say she's having difficulty in maintaing a stable eyewall structure. Nevertheless, it's still large and well organised. Still, don't let your guard down, it's nature anything can happen.
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Quoting Dennis8:


I agree..we can RELAX NOW


NO!
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I know many have been comparing this storm to Ike given the size and the relative low pressure given the sustained winds.

If anyone remembers, Ike gave one last attempt at building an eyewall as it was making landfall so just because Irene looks ragged right now doesn't mean that it can't quickly reorganize.
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Quoting 900MB:
Thanks Doc!
Wow, what a difference a few hours makes. Now there is only a 50% chance of seeing any hurricane force winds in the northeast, and only a 20% chance of surge high enough to flood the subways? While this may be pre-mature, I do indeed feel myself letting my guard down!


I agree..we can RELAX NOW
Member Since: August 15, 2008 Posts: 0 Comments: 446
She is undergoing an eye wall replacement cycle
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Quoting reedzone:


I disagree unfortunately.. but time will tell. People should not let their guard down.. Still a very dangerous storm.



I haven't seen any credible person saying let your guard down. The winds in Irene have been exaggerated by the NHC for over 24 hours. I think this is to keep people on guard. However, I believe that is the easiest way to lose credibility. Accurate information is the most important thing.
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Quoting ecupirate:


I will take the advice from the guy who has 20 years of experience and a doctorate in meteorology versus an internet blogger.

Just saying...


I think what Reed is most concern about is how quickly people will disregard the storm and falls in to a false sense of security. I also can't begin to imagine a storm this size and intensity would just go away in few hours, it just doesn't happen that way.
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Nanmadol... perfect symmetry, a very round eye...the hallmarks of an intense tropical cyclone.
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Focus one of your eyes to Nanmadol, it's more interesting, but it's not Atlantic....
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Quoting 900MB:


What change are you looking at?


I could very well be wrong, I am no expert, but just looking at the WV and Shortwave I see massive dry air coming in from the west through the south side of her and she's about to wrap it around her east side. I think people in here are starting to think I am troll..maybe I should just keep my mouth shut and go back to lurking.

http://www.ssd.noaa.gov/goes/flt/t2/loop-wv.html
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Thank you Dr. Masters for your update.It is nice to have information from someone with an education, EMOTIONALLY MATURE and respectful.
Member Since: August 15, 2008 Posts: 0 Comments: 446
Quoting 7544:
could she head back south west or south again ?
Umm, seriously?

No-se Jo-way.
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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.

From your lips to G-d's ears, Dr. Jeff.

Also, I would like the guerilla-pattern boot in pink, please.
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Quoting reedzone:
Eye has popped back on the newest frame of visible.. Oh and ragged? What are you looking at? the structure has improved since earlier this morning.



No more downcasting, this is serious stuff. A storm very similar to Hurricane Ike, pressure within Category 4 strength. I expect intensification to a 115 mph. Category 3 storm once again.


I believe they are looking at water vapor loops. Looks like crap on the SW to W sides.
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Quoting myrtle1:
will the track change since she weaker


Yes
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Quoting KEEPEROFTHEGATE:
no read it is not and may even lose cat 2 status


Sorry, I disagree. Irene will most likely keep at Hurricane strength till landfall on Long Island. I like the NHC track and intensity, makes perfect sense.
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I think Jeff Masters is downplaying the winds a little too much for New England. None of our worst Nor'Easters of the last 20 years had sustained tropical storm force winds for longer than 3 or 4 hours, for one thing.
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There's a reason I ignored Reedzone since last season. He's what I call an unintentional concern troll.
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Poof? There's the eye. Regardless of its intensity, stay vigilant.
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Irene is like, the Confuser. eye collapse, eye back. eye collapse, eye back. eye collapse, eye back.
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81. 7544
could she head back south west or south again ?
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waves were really good in cape canaveral today its rare to get it this good there were two red flags but hundreds of surfers are getting it
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Quoting reedzone:


I disagree unfortunately.. but time will tell. People should not let their guard down.. Still a very dangerous storm.
People should follow their local NWS and emergency management when it comes to a hurricane. Who is letting their guard down. Just because Dr M's forecast and yours do not totally agree is no reason for you to try and make them believe he is wrong and u r right. We get tired of it. Remember, people are not making their evac plans based on your forecast.
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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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