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

Armchair quarterbacking is a famous American sport, but it sure does get tedious to listen to...
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Quoting QacarXan:


Been wondering this too. Will the GFDL be right?


I hope not!!! That would stink for those of us in rain soaked upstate NY. The further east it is, the less damage it can do for all involved. I mean, someone has to be in the direct path it seems but the more of this storm that is out to sea, the better!
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Quoting wunderweatherman123:
im very angry the NHC is lowering the wind speed for irene. people wont take this storm seriously if they do this....
Listen, I would rather them to be accurate with facts than wrong with hype.

What people do not seem do understand is that some people overkill on preparation spending unnecessary time and funds that they may not have on some event that has on a extremely low probability of ever happening.

I've lived through 8 hurricanes in South Florida so I know that it does happen.

There just has to be a balance.

With that said, Irene is a wonky storm with more unique characteristics than the one I have seen in a long time.
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1026. A4Guy
to me, Irene looks less and less impressive with each click of the sat loop. maybe high-end cat 1 at landfall....high-end TS in the NY/NJ area.
I understand the caution with shutting down NYC mass transit...but I hope it turns out to be for nothing...though people will be even less likely to take a threat seriously "next time."
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hi guys i sure hop you this is the real me by looking at my join date
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When using Dr. Masters' blog, please refrain from posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself. Please do not engage in personal attacks or bickering. Material not conforming to these standards should be flagged with the button and ignored.

There is a hurricane that will make landfall on the United States East Coast within the next 24 hours...Let's stick on topic and talk about it. Don't worry about the Taz imposter, or the people who are downing this storm.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
1023. Thaale
Quoting Bluestorm5:
people accused the same thing when Ike hit... Ike had Category 2 winds, but Category 4 Storm Surge. Katrina landfalled as Category 3, but it had Category 5 storm surge that broke the record for all time. Irene is similar to Ike in size so the surge should be equal to Category 3 PLUS the tide is at the highest point of the month to add few more feet to the surge to make it Category 4 style surge.

The glass-half-full side of spring tide is that for the area (around NYC it looks like) where the highest storm surge comes during low tide, it will be the lowest low tide of the month.
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Quoting jonelu:
Its windier today here in WPB than it ever was when she was much closer. She is huge and I think the comparison to IKE are accurate...I think the storm surge will be a big problem with this one. Be prepared NE.


Tell me about it. We definitely dodged a bullet. Here in Western West Palm Beach we had all of two squal lines yesterday with a max gust of 25mph. Although I did have a couple pine limbs break off and litter the yard as a result.
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Quoting TropicalAnalystwx13:


More than likely.


OK. I sure hope you don't lose power!
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Anyone talking this storm down right now is a complete moron. Bill Read, the director of the NHC himself said earlier today he wished the saffir-simpson scale didn't exist for a storm like this. The wind field is massive, capable of producing an extremely dangerous storm surge. In addition, copious amounts of rain will fall up the east coast.

We should not discount wind damage either! I can't speak for the whole Northeast, but Eastern MA is full of old large trees that have been there for many many years in densely populated neighborhoods. Even TS force wind gusts of 50-70Mph would do tons of tree damage and cause massive power outages.

Refer to the NHC and your local officials for the best storm information for your area.
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Quoting WaterWitch11:

Well the spelling is questionable. Lol
the troll did do a little homework, but definitely an impostor!
Member Since: July 31, 2008 Posts: 0 Comments: 1320
Quoting AllStar17:


So if you disappear will it be because you lost power???


More than likely.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
Quoting SeniorPoppy:


Tell me what the power ball numbers are going to be on Saturday. Please
I have nothing to do with the lottery,the state gets enough of my money! But,watch Irene get stronger tonight.
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Quoting RTPGiants:
Being a long time lurker, but never poster, can I ask why people on this blog get so caught up in rooting for the storm to become stronger or weaker? Is there some sort of betting pool I missed?

Isn't it more important to analyze facts?


Well, aside from the people that look at these storms strictly from an objective position, you have people that want to see massive destruction...and as such root for the storms to gain instensity. Then, you have those who are terrified of these storms and their potential effects, and root for them to die. Additionally, to make it more fun, you have those who are strictly trolls and just want to get a rise out of people. Those people commonly say every storm is dying, falling apart or is over-hyped. You will learn who is worth listening to, and you will learn how to fill up your ignore list as well.
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Another cell coming at us... winds increasing to 15-20 mph.
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1008. ncstorm
I have to say I stopped watching the Weather Channel yesterday..its all about NY...for Irene to get to NY, she has to pass through NC..I dont call 6-11ft storm surge nothing to sneeze about in NC..The weather channel can kick rocks all I care..
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Quoting TropicalAnalystwx13:


LOL, yeah.


So if you disappear will it be because you lost power???
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1005. dewfree
looks more like Irene is bringging her pressure up to match the winds reather the other stated here.
Irene has had water temps galore to work with .forgive if im wrong,but isnt water temp the fuel for hurricane. she is inbetween now two boundaries . the first one she worked her way threw yesterday and the other she is pushing on now.
yes they both are weak at best . would that not inhibit her from bringing her winds to bare . I think she will have a cat 1 status when she meets land but isnt that a good thing in comparisonto the alternatives.
in june i came on into this blog and gave what i thought to be forecast of the atlantic hurricane season in my opinion and i quote it here:

11 storms 4 hurricanes 2 minimum hurricane hits :this was during a time the official hurricane outlook was 17 storms , I made that forecast based on analog and upper level patterns.I think there is a guy at accuweather that uses these same things to predict the outcome of tropical season and the winter that follows. last sept i put this on disk for the winter 2010 2011 for my area that we would get 2,3.5 to 5,8 to 12 inches of snow , we recieved 1.5,4,8,2.5 inch snows . pretty good huh and i live in an area that doesnt recieve very much snow or hasnt the last 30 years .in case your wondering north al .i will do the same this years as i have been doing this for a few years now . some people hate it some people have come to depend on it . i think them people that hate it ,we'll they will get over it . or not .who cares..mark my word on this storm and her impact of cat 1 status about 93 mph.remeber the place i said land fall would be between mertle and kitty hawk that was made when this storm was on south end of bahamas about 905 miles away. have a good day im out of here untill time of land fall .
dew
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Quoting Huskymaniac:
Is it me or does the center seem to be farther west than the models predicted?


Been wondering this too. Will the GFDL be right?
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Quoting Levi32:


Nope - worse.
alright and i know ive asked you this but are you still keeping your forecast as a cat 3 making landfall in NC or will you change it?
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Quoting AllStar17:


And you obviously still have power.


LOL, yeah.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
Quoting TropicalAnalystwx13:


I've been in the outer bands, the winds aren't THAT strong...Maybe some gusts UP to 35 mph, but that is it, so far.


strong enough for the relatively low amount of power outages reported.
Member Since: November 17, 2010 Posts: 11 Comments: 527
I don't think we should keep out of mind that Irene will be a dangerous storm to say the least. I think the fact the weather channel is going to update it to catastrophic in terms of effects is ridiculous I think. It might have something to do with validating some of the obscene and vulgar enforcements that are occuring in the Northeast due to a potential Tropical storm or hurricane.
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Quoting TropicalAnalystwx13:


I've been in the outer bands, the winds aren't THAT strong...Maybe some gusts UP to 35 mph, but that is it, so far.


And you obviously still have power.
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Is it me or does the center seem to be farther west than the models predicted?
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Quoting Levi32:


I think catastrophic would be if Irene was a Cat 4 or Cat 5, not that damage won't be severe there.


Yeah, we're rather used to storm systems in the 2-3 strength, we'll be ok.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
Quoting ShenValleyFlyFish:
So how sre things in Gulfport MS post Katrina?


That I could not tell you but I can tell you Bolivar Peninsula is still flat from Ike
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09L/MH/I/C2
RI FLAG (off)
RD FLAG (flag)
MARK
32.25n/76.98w





ALWAYS FOLLOW NHC/TPC FORECASTS FOR ALL WARNINGS REGARDING THIS STORM
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Quoting SeniorPoppy:


That's true but a cat 1 storm surge is nothing compared to what they were calling for even last night.
people accused the same thing when Ike hit... Ike had Category 2 winds, but Category 4 Storm Surge. Katrina landfalled as Category 3, but it had Category 5 storm surge that broke the record for all time. Irene is similar to Ike in size so the surge should be equal to Category 3 PLUS the tide is at the highest point of the month to add few more feet to the surge to make it Category 4 style surge.
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Quoting Gorty:


Right, that means my NWS has me which is far from the coast in western Mass, has wind gusts to 80 mph and sustained winds increasing from 45-55 to 45-65 mph. But no, you are far more experienced than the people at my NWS...

-sarcasm-


Granted those are some strong winds but Armageddon is not going to be raining on you.
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09L/MH/I/C2
RI FLAG (off)
RD FLAG (flag)
MARK
32.25n/76.98w





ALWAYS FOLLOW NHC/TPC FORECASTS FOR ALL WARNINGS REGARDING THIS STORM
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Its windier today here in WPB than it ever was when she was much closer. She is huge and I think the comparison to IKE are accurate...I think the storm surge will be a big problem with this one. Be prepared NE.
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Quoting SeniorPoppy:


That's true but a cat 1 storm surge is nothing compared to what they were calling for even last night.


Storm surge for this system will be 1 category higher than what would normally be expected for whatever strength this storm ends up being by then, due to its size. See Hurricane Ike for more details.

Being here in New England, where I can see the NY and New England stations both.... none of them were really calling for more than a Category 2 surge, which is still fairly consistent with what will probably occur
Member Since: November 17, 2010 Posts: 11 Comments: 527
Quoting ConnecticutWXGuy:
\

there is actually rather strong winds judging by the live video feeds showing these outer bands. It is more than just raining.


I've been in the outer bands, the winds aren't THAT strong...Maybe some gusts UP to 35 mph, but that is it, so far.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
Quoting ConnecticutWXGuy:


the real taz knows how to speak English and spell.

Well the spelling is questionable. Lol
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Quoting Levi32:
Clearly a very unhealthy SW quad and an attempt at a double eyewall:



Based off that image I have a VERY difficult time believing Irene will even maintain her strength let only strengthen. It's entire southern half has been eroded. Those things don't fix themselves overnight. Even still massive windfield 75+ over a 150 mile area is still a very real threat to lives. Not too mention I am very curious to what type of surge we will see with this storm with its pressure being way down there around 950 mb range.
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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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