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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was just checking out the severe weather map in WU, noticed the air quality advisories due to Great Dismal Swamp fire... hopefully Irene can put that out, and cross off one good deed on her checklist ;)
Member Since: July 31, 2008 Posts: 0 Comments: 1320
Quoting P451:


So what is that then? A giant butthole?





I think some people have just forgotten what storms begin to look like in the higher latitudes - and mistaken them for storms they've watched decay while still in the deep tropics.

It's just not the same processes at work.

While Irene does not have a fantastic structure it is still a solid Cat 2 hurricane that is actually improving some right now.

Maybe the TWC "It can happen tomorrow" bogus crap about a Cat 5 hitting NYC has people stirred up to think that this system, since it doesn't look like Katrina did in the center of the GOM, that it's now a nothing storm.

The increasing baroclinic nature of systems that push further north also keep the winds up even as the storm itself loses it's punch. The wind field also expands dramatically northward.

A 75mph - 100mphG hitting western LI late Sunday afternoon is a very good bet.

Torrential rains is a very good bet.

High surf is a very good bet.


And, as I will repeat until we reach that milestone, until the system interacts with NC tomorrow, we do not know exactly what to expect in NJ/NY/CT.

However, given all the data gathered which has to be an unprecedented effort, I think the forecast track is very very solid - much more trustworthy than usual.



Actually going to Long Island to visit family and friends about a month from now.. Now expecting to see damage.
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Nanmadol: My eye is better than yours.
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165930 3118N 07711W 6962 02814 9642 +118 +052 138072 073 058 010 00
170000 3117N 07712W 6966 02799 9619 +129 +052 137073 074 060 009 00
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170730 3057N 07732W 6973 02696 9490 +154 +073 327015 017 /// /// 03
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170900 3058N 07738W 6967 02716 9489 +171 +077 336035 038 035 000 00


Looks like they're trying to get a fix on the pressure in the eye.
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375. Vero1
Quoting Gorty:
Henry M's Tweet:

"We expect thousands of trees to be blown over and/or damaged by Irene from North Carolina to New York and New England."
As a reminder from NHC

EVEN THROUGH THE SYSTEM IS WEAKENING...THE THREAT OF STRONG INLAND
WINDS WILL REMAIN FOR A LITTLE WHILE LONGER. OF PARTICULAR CONCERN
IS THE POTENTIAL LOSS OF LIFE DUE TO FALLING TREES
. INLAND FLOODING
WILL ALSO CONTINUE TO BE A HAZARD.

FORECASTER FRANKLIN
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT MON AUG 29 2005
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Quoting franck:


If the cloud tops were cooling again, then the storm would be reintensifying. So long as the cloud tops are continuing to warm, as has been the case since the moment the eyewall collapsed, the storm is dying.


lmao
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Quoting PrivateIdaho:


Hahahah! New to me!

whippersnapper
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It may just be me but I still expect IRENE to start firing reds again in convection later tonight once you get the daytime cooling, etc... while she may not strengthen much, it may allow for some of the winds currently above the surface to work their way down.

With the cloud pattern, IRENE is looking the best it has in a while, with outflow on all sides now.
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Quoting MahFL:
The eye is also tightening......plays "Jaws".....music.....
It looks like there is a small eye refoming even though Dr Masters does not think this will happen. Crazy business here!
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Quoting ncCANEiac:
Is it just me or is the eye reforming and eyewall rebuilding??


If the cloud tops were cooling again, then the storm would be reintensifying. So long as the cloud tops are continuing to warm, as has been the case since the moment the eyewall collapsed, the storm is dying.
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367. MahFL
Quoting Gorty:
Henry M's Tweet:

"We expect thousands of trees to be blown over and/or damaged by Irene from North Carolina to New York and New England."


More like 100's of thousands....
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She will miss the next tropical forcast point to the west.
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Her eye (31N 77.4W) just hit the east side of the gulf stream within the last hour. She is in it now untill she is about 50 miles off the NC coast.

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Irene's new eye starting to peek out?

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363. MahFL
Quoting ncCANEiac:
Is it just me or is the eye reforming and eyewall rebuilding??


It's reforming....again....
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Quoting ecupirate:
Irene will not get into the warmest gulf stream waters untill about 33N. She is and has been in cooler water.

she will pep up
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Is it just me or is the eye reforming and eyewall rebuilding??
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Link

BIG wobble west. click tropical forcast points
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359. Gorty
Henry M's Tweet:

"We expect thousands of trees to be blown over and/or damaged by Irene from North Carolina to New York and New England."
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358. MahFL
Progress Energy is reporting 2247 outages at the moment, they are proberbly not directly due to irene though.
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356. HCW
3 days ago I saw Alabama power trucks about 30 of them headed for the Carolinas.  That is what it's about . And thanks to PIke Power in NC for restoring my power after Katrina  :)
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The surge is always what I fear most! : )
"Run from water, Hide from wind."
Quoting hurricanejunky:


I'm certainly not downplaying wind. That will be a problem for some but the primary threat likely won't be wind but the rain and surge which will cause catastrophic flooding in some areas.
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pretty sure now we will finally have our first landfall in a long time good luck to everyone
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Quoting ReefMaster:

May not be due to anything more than normal shutdown before the storm. Power lines not required for lifesaving (hospitals, etc.) are far safer with no juice flowing.


brevard county florida had a large amount of power outages from the winds and we barely had anything noticeable.
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352. MahFL
The wind at Wilmington finally reached a steady 20 mph, it's all downhill from now on.
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351. 900MB
Quoting ecupirate:
Irene will not get into the warmest gulf stream waters untill about 33N. She is and has been in cooler water.



Looks like she is wobbling her way to warmer waters.
Member Since: June 11, 2006 Posts: 0 Comments: 663
Plenty of time to regain cat 3 status,do not let this temporary Eyewall replacement fool ya,storms do this all the time.
Member Since: June 24, 2007 Posts: 0 Comments: 1460
Quoting Vero1:
As in tportionhe past they will blame the government for not taking care of them.
You got a secure job to offer em? Beside which a large portion are mentally ill. Course can't spend any money on them, no boost to the economy, I know lets give em a tax break. Conditions are grim on the streets, more so during inclement weather.
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Quoting MahFL:
Duke Energy has only 76 reported outages at the moment in NC.


Duke energy is not that prevelant on the coast of NC. Most of the power users are progress and as you go north you get into dominion.
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only updates every 6 hours
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345. MahFL
The eye is also tightening......plays "Jaws".....music.....
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May make the 2pm and 5pm Updates interesting. Looks like the ridge is trying to fight back since this morning's runs
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Quoting zawxdsk:
News Media already reporting power outages on the North Carolina coast. Don't know that I believe that. I suppose regular thunderstorms can do that...

May not be due to anything more than normal shutdown before the storm. Power lines not required for lifesaving (hospitals, etc.) are far safer with no juice flowing.
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342. HCW
http://www.chart.state.md.us/video/video.asp?feed =37003b8e0098007b00488436cf235d0a traffic slugging westward along U.S. 50 at the Kent Narrows Bridge.

http://www.chart.state.md.us/video/video.asp?feed =2f0013b20094007b00488436cf235d0a check out the traffic backup on U.S. 50 at Maryland 404.

http://www.chart.state.md.us/video/video.asp?feed =3aff0a92008500bb004b8436cf235d0a - this could be a fun one to watch as winds start kicking in (Ocean City Drawbridge - U.S. 50).



Deldot Traffic Cams (click to see the Sussex Co. Cams).

The one at DE 1 & DE 24 shows heavy northbound traffic.
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My thoughts and prayers with all the People in the path of Hurricane Irene.
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340. MahFL
Duke Energy has only 76 reported outages at the moment in NC.
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Question for the pros- is all shear created equal, or does it matter which quadrant the shear hits the storm?
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From CNN. I'm sorry, this really isn't funny because it's a worst case scenario for NYC, but when you read that line about wallstreet...

JFK airport would go under an astounding 20 feet of water. The famous Fulton Ferry boat landing in Brooklyn, a popular spot for young couples to take wedding pictures, could also end up under water. Wall Street could find itself in deep water - about 7 feet. The subway system could also be knocked out



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337. Gorty
Quoting hurricanejunky:


I'm certainly not downplaying wind. That will be a problem for some but the primary threat likely won't be wind but the rain and surge which will cause catastrophic flooding in some areas.


In western Mass I am in, I am under a TS watch and I could get both damaging wind and flooding rains. Not good.
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Irene will not get into the warmest gulf stream waters untill about 33N. She is and has been in cooler water.

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Quoting ShenValleyFlyFish:
Link


Hahahah! New to me!

Member Since: August 29, 2010 Posts: 0 Comments: 5236
Not to tempt fate, but I would be very surprised to see Irene landfall with winds above 100mph, let along reach CAT 3. The structure is just too poor and the cloud temps are far too warm. If you compare the storm to 24hrs ago the intensity is hugely diminished. It's surprising. Even given the dry air and shear two days ago I was expecting a CAT4 storm at this point in time.

It seems that despite ideal conditions Irene grew very large early on without ever really gaining a decent eye wall structure. Her size has only encouraged a lack of balance and that imbalance has only exaggerated the effect of dry air and shear. Consequently even with pressure falls she's never been able to capitalize on the SSTs. Which has been very good fortune.

Nonetheless, still very dangerous and certain to cause major disruption, but perhaps could have been a lot worse. That said, we are still about 20hrs from landfall. I always enjoy following the blog, drama and all. It seems a lot of people are caught between wanting minimum human (aka continental US) impacts and wanting to see these systems become as intense as possible - and there are plenty of people who seem to enjoy the panic. Let's just keep rational, alert and learn what we can. Good luck to all those in the firing line and keep safe.
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333. HCW
5% nado risk on the coast

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P451- Still exhibiting the curly-cue motion you pointed out yesterday, which by the way was an excellent description of how large storms move.
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News Media already reporting power outages on the North Carolina coast. Don't know that I believe that. I suppose regular thunderstorms can do that...
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Quoting Gorty:


People keeps downplaying the LARGE wind field of damaging winds that will affect NE and New England.


I'm certainly not downplaying wind. That will be a problem for some but the primary threat likely won't be wind but the rain and surge which will cause catastrophic flooding in some areas.
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329. MahFL
Bagdad Bob just told me "there is no eye in the hurricane".





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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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