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 drg0dOwnCountry:

That, sir is an EWRC ongoing. i can see 2 eyewalls.
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Interesting...

Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KNHC)
Transmitted: 26th day of the month at 16:18Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Mission: Non-Tasked Mission, possibly not tropical (flight in the North Atlantic basin)
Mission Identifier: 110826145138302 (2 digit year/2 digit month/2 digit day/6 digit mission start time/Last 3 digits of aircraft tail number)
Date Mission Started: August 26th in '11
Time Mission Started: 14:51:38Z
Observation Number: 05

Part A...

Date: Near the closest hour of 16Z on the 26th day of the month
Highest Mandatory Level For Which Wind Was Reported: 400mb
Coordinates: 19.5N 68.4W (View map)
Location: 120 miles (194 km) to the NE (54°) from Santo Domingo, Dominican Republic.
Marsden Square: 043 (About)
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Update
*All graphics can be magnified by clicking on them (they can also be further magnified in the new window by clicking on the graphic)






Member Since: June 29, 2009 Posts: 13 Comments: 5313
Quoting AussieStorm:
WTH!!!!!

It's actually a glitch. Nanmadol did not make landfall.
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If Hurricane Irene's eyewall has collapsed, why is it that her eye is reappearing as per the RGB and visible channels?
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Pressure continuing to rise in Irene. Latest VDM has it up to 949 mb.
Member Since: June 29, 2009 Posts: 13 Comments: 5313
Latest Dvorak looking pretty weak

Link
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Quoting 53rdWeatherRECON:
Wow look at the feeder bands appearing on visible! That's pretty cool to see, they dont call them feeder bands for nothing. These combined with her symmetrical core will allow her to reintenisify to a CAT3 as the NHC ha forecasted to pass the Outer Banks.

The distance before landfall is still pretty far and she will hit some really warm gulf stream waters that her surge will push into every bay on the east coast. The surge alone will make it so she doesn't even technically make a "landfall" in N.C.

She will start puffing cold cloud tops around her new eye again by this evening just like she did yesterday.

CAT3 by 11pm.

It remains a possibility for sure,keep an eye on that pressure for a look at what she is doing!
Member Since: June 24, 2007 Posts: 0 Comments: 1471
269. MahFL
Irene is like the Rocky films....she's on about the 5th re-make already ! And looking good too....must be all the plastic surgery......
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WTH!!!!!

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Quoting EastTexJake:
What I'd be most worried about in NYC or any really big city, is the number of indigent, government dependant people, whom rarely plan for disaster. What's going to happen if they wake up to find the power out, no fresh water, the busses and trains don't run, and the streets are clogged with debris, making it impossible for law enforcement to respond, even if the police and fire crews weren't already all busy. The storm wont kill that many I think, but the aftermath might be a warzone.


This kind of smacks of condescension. I don't know if that was your intention - agreed that the aftermath could be very difficult. But indigent people in Manhattan? Have you been there lately?
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Quoting EastTexJake:
What I'd be most worried about in NYC or any really big city, is the number of indigent, government dependant people, whom rarely plan for disaster. What's going to happen if they wake up to find the power out, no fresh water, the busses and trains don't run, and the streets are clogged with debris, making it impossible for law enforcement to respond, even if the police and fire crews weren't already all busy. The storm wont kill that many I think, but the aftermath might be a warzone.
NYC(Manhattan) isn't really filled with ghettos as it was years ago. What low income areas there are are very limited and pretty much all towards the upper end of the Island.
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Quoting SPLbeater:
Looks to be an eye underneath some high level clouds in the center...i think. See my last comment


No eyewall = no eye. Only a center of circulation.

However, there are still hurricane force winds, heavy rains, and storm surge ahead.
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Wow look at the feeder bands appearing on visible! That's pretty cool to see, they dont call them feeder bands for nothing. These combined with her symmetrical core will allow her to reintenisify to a CAT3 as the NHC ha forecasted to pass the Outer Banks.

The distance before landfall is still pretty far and she will hit some really warm gulf stream waters that her surge will push into every bay on the east coast. The surge alone will make it so she doesn't even technically make a "landfall" in N.C.

She will start puffing cold cloud tops around her new eye again by this evening just like she did yesterday.

CAT3 by 11pm.

Member Since: August 5, 2005 Posts: 2 Comments: 80
Quoting rv1pop:
I right click on the ignore button; click on open in a new tab; go through the instructions, then close the tab and I am back to where I was. HTH POP


That works great! Thank you.
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on wunderground for irenes hurricane hunter info, it shows the HH found a pressure of 939mb
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Quoting P451:


Keep swallowing up that dry air, Irene!
Member Since: June 29, 2009 Posts: 13 Comments: 5313
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Quoting oracle28:


Not a dumb question, in fact, one of TWC experts (Lyons, perhaps) added that the taller buildings in large cities (Houston, NYC, Miami) can experience wind gusts of a category higher than the ground level.


oh wow, that certainly changes things. thanks
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Quoting flcoopercrew:
this is probably a dumb question but i am gonna ask it any way. last time i was in nyc the wind in between the buildings was crazy strong. wouldn't that mean stronger winds in the city during a hurricane? (the whole wind tunnel thing?)


My insurance adjuster after Rita said that Tropical Storm Allison after it hit downtown Houston was where they learned about the wind tunnel effect. Wind being squeezed between building sides increased in velocity. Kind of like putting your thumb over the end of a hose running at a certain speed and then the water shoots out alot furthur when forced out a smaller orifice. Our homes close together and it peeled the stain off the sides (between homes only) in sheets and made my bushes literally become curly cues. Weird sight. That will be a problem with NYC even with below Hurricane force winds.
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What I'd be most worried about in NYC or any really big city, is the number of indigent, government dependant people, whom rarely plan for disaster. What's going to happen if they wake up to find the power out, no fresh water, the busses and trains don't run, and the streets are clogged with debris, making it impossible for law enforcement to respond, even if the police and fire crews weren't already all busy. The storm wont kill that many I think, but the aftermath might be a warzone.
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Off shore from Edisto Island SC. 21' waves.

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HWRF @ 126hrs tryies to develop something at approx 38W 11N

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Quoting donna1960ruled:
last 3 frames.....looking significantly on the improve.


U looking at infared or visible. Looks ok at visible, but worse on infared.
Member Since: July 27, 2011 Posts: 0 Comments: 204
Quoting Jeff9614:


Do they sell generators at Target?<


I don't think so, but I've seen them at Harbor Freight and some auto parts stores. Call ahead to save some time.
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20-frame visible loop
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09L/MH/I/C2
RI FLAG (off)
RD FLAG (flag)
MARK
30.48n/76.98w





ALWAYS FOLLOW NHC/TPC FORECASTS FOR ALL WARNINGS REGARDING THIS STORM
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as pressure drops wind radius will expand. less intensity but greater overall coverage.
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Quoting flcoopercrew:
this is probably a dumb question but i am gonna ask it any way. last time i was in nyc the wind in between the buildings was crazy strong. wouldn't that mean stronger winds in the city during a hurricane? (the whole wind tunnel thing?)


Not a dumb question, in fact, one of TWC experts (Lyons, perhaps) added that the taller buildings in large cities (Houston, NYC, Miami) can experience wind gusts of a category higher than the ground level.
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The Water vapor loop tells the story....

Link
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At noon from a buoy 20 SE of Cape Fear NC
Wind ENE at 33+41 Kts,
Waves SSW at 14 feet
Press 29.71 and falling
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They are just lucky... Irene missed us, I hope it will be for September...
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238. 900MB
Hmmm, looks like she is trying to "eye up" a bit. I've seen canes take dry air in and build an eye with it before and then ventilate better. Who knows..anything is possible over the gulf stream.
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Quoting HiWay:


Thank you! The wind is not the problem. So many people will see cat 2 or cat 1 before it hits the NE and think "Oh, well no big deal then." Problem is the ground is saturated, strong gusts will still take down trees and power lines and the surge and rain hasn't gone anywhere.
Isabel hit at 105mph and cut an inlet south of Cape Hatteras,so it could happen in the same place. We still had 80 mph gusts from it here in Northeast N.C. too strong to stand up in!
Member Since: June 24, 2007 Posts: 0 Comments: 1471
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Quoting JerseyShoreGirl:
I am going to wait to see what happens in NC before I jump the gun here in NJ. I will still head all the warnings, but the last update actually makes me feel a bit more calm.


If you're in no danger of flood/surge I'd just wait and see what your local emergency management says. Usually can't go wrong with that plan. They usually have the best information to make decisions with.
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this is probably a dumb question but i am gonna ask it any way. last time i was in nyc the wind in between the buildings was crazy strong. wouldn't that mean stronger winds in the city during a hurricane? (the whole wind tunnel thing?)
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Looks to be an eye underneath some high level clouds in the center...i think. See my last comment
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Still some favorable pockets of atmosphere to the north with upper air diffluence, plus a potent northern stream jet to ventilate the storm as it goes extra-tropical. Get a storm loop of the Charley 2004 and watch the last 8 hours to see rapid, unpredictable intensification.
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230. HiWay
Quoting overwash12:
Irene could still strengthen a little,but that doesn't really matter too much given the size of this storm. Imo


Thank you! The wind is not the problem. So many people will see cat 2 or cat 1 before it hits the NE and think "Oh, well no big deal then." Problem is the ground is saturated, strong gusts will still take down trees and power lines and the surge and rain hasn't gone anywhere.
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229. 900MB
Quoting ILwthrfan:
We are approaching Dinurnal minimum as well so that is playing a factor into her warmer cloudtops.


She does have a tendency to blow up at the end of the day. Guess one more chance.
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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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