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 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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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 noticed the eye too on the last frames
Member Since: September 22, 2005 Posts: 11 Comments: 2032
When will the next Microwave data be available?,
we can really see the storms structure clearly with that.

The last pass did show that the inner eyewall indeed has collapsed, bit there was also a hint of the spiral bands trying ti form a new one
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Irene looks like crap. Eyewall is gone, cloud tops are warming, and her SW side is drying out.
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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 will take the advice from the guy who has 20 years of experience and a doctorate in meteorology versus an internet blogger.

Just saying...
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I dunno.

While she may be in a less organized state at the moment, all available dynamical modeling calls for a lowering central pressure for the next 18 hours (except NOGAPS, which just maintains).


(click for full size)


Not a surprise, given the gulf stream. Dry air and shear are the reasons why not, as usual.
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will the track change since she weaker
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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.
no reed it is not and may even lose cat 2 status
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Quoting NCSCguy:
Over 5000 people without power in charleston county


OH MY GOD!!!!!!!!!!!!!!!!!

Oh, the humanity..........
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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.


Hey Reed! What about the Watervapor Loop?

Link

The last think I want to do is give the false immpression to people by posting incorrect data, but I just though maybe looking at the data at hand she was loosing the battle. Do you see the dry air entrapment increasing on her west south and now going for her southeast side?
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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.


You're right about people not needing to let their guard down. I doubt they will either. Dr. Masters emphasized the surge potential and that should be enough.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
It does appear ludicrous, but look at the graph; the storm was pierced with an arrow...bullseye.
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Quoting MississippiWx:


No reason to cause panic and give out false information to make the storm seem worse.

Dr. Masters is correct that Irene is probably done strengthening.


I disagree unfortunately.. but time will tell. People should not let their guard down.. Still a very dangerous storm.
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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!
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09L/MH/I/C2
RI FLAG (off)
RD FLAG (flag)
MARK
30.28n/77.08w





ALWAYS FOLLOW NHC/TPC FORECASTS FOR ALL WARNINGS REGARDING THIS STORM
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Quoting reedzone:
Apparently Dr. Masters doesn't believe the storm will be as bad as forecasted.. Watch what you say sir... NO ONE should let their guard down, continue preparing for a very Historical storm.


That is not what he said at all. He was very clear that the storm surge could be the ugliest part of Irene. I think many will be surprised by just how much surge a giant Cat 1-2 storm can bring with it. He also pointed out that flooding will be a major concern.
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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.
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Quoting franck:


Well, it may take four to six hours, but the storm was never a titan, it was a slug, and it is still offshore quite a ways. Outer bands will collapse very quickly, and the inner core will as well in some hours. A collapsed eyewall can be just like shutting off an engine. A hurricane is an engine.


I get all that, but it could just as easily maintain itself, as it has been. It still has to cross the Gulf Stream, which could just as easily re-fire the engine somewhat. I think it's very pre-mature to assume it's going to collapse.
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Quoting robodave:
The amount of energy doesn't even cross my mind. In 1900, do you think people could have imagined nuclear power? Probably not. So the last thing I'm going to do is be pretentious about what we can and can't do in the future. I just trust that putting funding into this will produce information that we can use. It may not be fruitful right now or even in the near future, but it may some day. It's better than doing nothing at all. No one knows the future, so we may as well try.



I read somewhere that the amount of energy released by an average mature hurricane is 200 times the world's electrical generating capacity. I am neither an engineer nor a scientist, but I know enough to recognize that it would take an equivalent amount of energy to accomplish what seems to be your goal - to prevent that tropical system from affecting populated landmasses. I bet you could confiscate the wealth of every person on the globe and still be far short of your goal. So, you say "It's better than doing nothing at all," to which I ask "what" is better than doing nothing at all? Who is to fund the "what"? Is everyone on the globe to starve in order to fund the "what". And, to what end?
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Over 5000 people without power in charleston county
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Quoting reedzone:
Apparently Dr. Masters doesn't believe the storm will be as bad as forecasted.. Watch what you say sir... NO ONE should let their guard down, continue preparing for a very Historical storm.


No reason to cause panic and give out false information to make the storm seem worse.

Dr. Masters is correct that Irene is probably done strengthening.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
I'm not trying to be disrespectable, just looking at the recent loops she's really starting to get choked off. her core is really struggling.

This doesn't mean that it still isn't going to effect people. I just think she's heading down hill, think maybe NHC maybe seeing this as well.

This has been a weird storm. 946 mb pressure with only 105 mph winds. They even made notes on having to use a larger factor scaling flight level winds down compared to other hurricanes? Reminds me of Alex going into Texas somewhat.
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Quoting ILwthrfan:
This storm is going Poof!





Why don't you check back in few days and ask the millions w/out power, damage to their homes, autos etc...and God forbid any deaths, what they thought about your "poof" forecast!! Oh...btw...."poof" to you.
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Quoting ILwthrfan:
I can't believe no one is noticing the struture change of this storm over the last 2 hrs!!!!!!!!!!!!


What change are you looking at?
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What happend to "Grandpato4"?
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Quoting kilgores97:


Yep, it's all just going to go away and the sun will magically appear.


Well, it may take four to six hours, but the storm was never a titan, it was a slug, and it is still offshore quite a ways. Outer bands will collapse very quickly, and the inner core will as well in some hours. A collapsed eyewall can be just like shutting off an engine. A hurricane is an engine.
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Quoting RickWPB:

This is good advice. If you're not real familiar with back roads but have a GPS, you can try setting your GPS to avoid freeways. This could steer you along the back roads.


Id be wary about using the GPS for backroads. Every year there are several accounts of people trusting the GPS and becoming lost and stuck or broken down on deserted roads. Some people lose there life because of being snowed in or stuck in the desert. If you must try alternate routes, stay to the higher grade state hi-ways, don't trust county roads as they're often washed out and sometimes the GPS info is incorrect about them.
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Quoting reedzone:
Apparently Dr. Masters doesn't believe the storm will be as bad as forecasted.. Watch what you say sir... NO ONE should let their guard down, continue preparing for a very Historical storm.
Sure did not hear him say anything about letting our guard down. Sounds like u are putting words in his mouth. He is a big boy and can speak for himself.
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Quoting sullivanweather:


HA! That's how you fools always get your fun to end. Spend a whole day waiting around for your 24-hour probation period to end to troll the blogs day after day. I bet your friends must think you're the coolest.
Oh, what's that?
You have no friends?
Huh?


Why, when people are seeking negative attention, do we insist on rewarding them? Ignore, and once these peeps realize they won't gain anyone's attention, they will go somewhere else.
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23. Breaves 3:24 PM GMT on August 26, 2011

replaced with empty space
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Quoting reedzone:
Apparently Dr. Masters doesn't believe the storm will be as bad as forecasted.. Watch what you say sir... NO ONE should let their guard down, continue preparing for a very Historical storm.


He thinks the maximum winds may not be as bad, but he is definitely still considering the surge as a major threat.

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Quoting reedzone:
Apparently Dr. Masters doesn't believe the storm will be as bad as forecasted.. Watch what you say sir... NO ONE should let their guard down, continue preparing for a very Historical storm.


Isn't this his blog? And isn't he the only meteorologist posting right now?

And the storm looks ragged right now.
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It's really awful
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Your life must really suck if you have to entertain yourself by trolling a WEATHER blog. Anyway, it's nice seeing the empty space.

Use your ignore buttons and don't talk to it.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
23. Breaves 3:24 PM GMT on August 26, 2011

not a good thing posting false info even if its a joke
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Quoting ecupirate:


You best calm down son.

I will work you, you stinking muff cabage


You little redneck. Your 20 year old pick up truck might get rained on.
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38. HCW
Irene Stats

Member Since: August 10, 2002 Posts: 0 Comments: 1409
37. jpsb
Quoting franck:


Actually, it could be possible, winds, convection, everything gone within a few hours.
I remember Don going poof earlier this year when it ran into the Texas high from h*ll. Don evaporated right before my eyes.
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WU used to have a no-tolerance policy of off topic and absurdity immediately resulting in a handle no longer being able to post anything for either a day-plus duration or never again.

I suppose that's just a fond memory, now.
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Nice to see another major tropical storm biting the dust. While any hurricane can be dangerous, I think the media coverage can be far more so, especially if the storm isn't as bad as projected...

Thanks for the update, Dr. Masters...
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I can't believe no one is noticing the struture change of this storm over the last 2 hrs!!!!!!!!!!!!
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Quoting franck:


Actually, it could be possible, winds, convection, everything gone within a few hours.


Yep, it's all just going to go away and the sun will magically appear.
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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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