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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Good bye NYC. Hope to see you again someday.
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Quoting DrMickey:

Re: post 540: Anyone notice the "Virgin of Irene" who appears in the lower right of the last frame in the image?
Can't copy the loop, so check post 540 and see...


yes, in the SE corner of Irene's circulation where it meets the Bermuda high, looks like some kinda spin.
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777. 7544
Quoting mcluvincane:


Your eyes must b crossed
nt

as log as it doesnt start jogging south lol but who knows she hasnt give us any surpises yet other than streghth so far
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Quoting leftlink:
It is falling apart, storm is getting chewed up by dry air.

See 4 last frames of infrared (at 30 min intervals, ending 10 min ago). Whatever convection formed in the center has smashed into bits:

LAST 4 Images

If it strengthens just before landfall, it will only be because the pressure has risen so much that it again will have room to fall (a 970mb storm over 87degree water could start to build a core and even maintain that over the coast).


Goodbye Irene. Hello dry air.
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<
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Quoting GaltsGulchCO:
a dry air "dagger" has been spiral of archimed-ing toward Irene's heart the past 60 minutes. see if it can strike at the core...

,as i said 80-90 mph cane landfall obx imo
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Quoting Bluestorm5:
Johnston County is under High Wind Warning. Wake County is NOT.


Ah..I see. Thanks.
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772. Gorty
Looks like N with NNE jog than back to N. But mean direction is N.
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Quoting RavensFan:

no doubt! but still its not the monster it was looking like it was going to be last night. though still a VERY powerful storm and with most storms its size and given its former strength, its going to have a large storm surge! So treat it like it is a very serious storm Northeast!!!


A tropical storm.
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Hi everyone. I'm a long-time lurker, and I love the information that is posted here.

I find the discussion of 'over-hype' vs. 'under-hype' to be unfortunate. I say this because the argument is over obvious points.

1. If we knew Irene would look this way at this time yesterday, the opinion of people would be different when it comes to concern and outlook -- at least some people. And, one person's over-evaluation is another's under-evaluation.
2. If the models are wrong, then this is not a shock because models aren't always right. I've seen countless times the idea recalled that people are a necessary part of the equation of forecasting. But, people make mistakes too. Maybe Irene will increase in strength, or maybe it will weaken considerably. In post-season analysis, we will learn why, and tune models to try and account for what we missed.
3. The NHC, as an agency made with the public interest and economy as top priority, states not only the facts, but an explanation of risk. They must tell us what could happen, not just what is happening.
4. The media will sensationalize because money talks. It takes a critical eye to filter out the excess and come to the facts. Not everyone has that ability, simple as that.
5. There is always the 'what if' factor. What if the storm is stronger than it looks? What if the track is as bad as it could be? There is practical, plausible risk. People need to act and be informed.

So, with all of that said, it doesn't matter if over-hype is happening. People need to know and we need to understand it is expected. Lessons will be learned regardless of the outcome.
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It is falling apart, storm is getting chewed up by dry air.

See 4 last frames of infrared (at 30 min intervals, ending 10 min ago). Whatever convection formed in the center has smashed into bits:

LAST 4 Images

If it strengthens just before landfall, it will only be because the pressure has risen so much that it again will have room to fall (a 970mb storm over 87degree water could start to build a core and even maintain that over the coast).
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Quoting reedzone:


People just don't understand how dangerous this storm is..

I hope they do soon. downcasting is the last thing people that have never seen a major hurricane need. trust me i live in tampa, people here have no idea...
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Quoting tiggeriffic:
HMMMMM....this is for all those who posted earlier... the President is cutting his vacations short...him and the entire family are leaving Martha's Vinyard today and returning to DC...and btw...it was on CNN just a few weeks ago...the current pres has taken less vacation days upto date than either of the Bush boys or Reagan...guess he does care


Well the Bush and Reagan vacationed at their private ranches, which were in effect secondary White Houses. So basically working vacations.
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Quoting ConnecticutWXGuy:


apparently you think they should say NNW or NNE if the direction is even a fraction of a degree off of complete due north. But there is a guideline as to what direction is what.

Hey no fair! That wasn't on the No-Child-Left_Behind test cribsheet.
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Quoting ConnecticutWXGuy:
So here's a question for you whiners about "oh the media over-hyped the storm."

What is better? over-hyping, or under-hyping? Because unless you can make perfect forecast without any chance of being wrong... one or the other is always going to happen. Do you suggest that the media takes the current forecasts and downplays them? Because as much as I disagree with a lot of what the media does, they certainly have not "up-played" this storm and its potential all that much at all. So if what forecasters and the media have been saying is "over-hyping" Irene... then I can only assume what you desire is for them to downplay every forecast until a hurricane is virtually on-top of any given forecast landfall.


You have a valid point but the problem that the media (especially the NWS) faces with "up-playing" a storm before landfall is that if the storm arrives and it turns out to be a rain shower at most; the NWS is under the gun. All the people (that are clueless) blame the NWS/media for the "headache" they caused them.

I agree its far better safe than sorry but its a double edged sword for the NWS/media.
Member Since: August 18, 2011 Posts: 0 Comments: 597
Quoting GaltsGulchCO:
a dry air "dagger" has been spiral of archimed-ing toward Irene's heart the past 60 minutes. see if it can strike at the core...



At this rate, Irene is going to be a low end category 1 when it strikes nc.
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763. Gorty
Quoting reedzone:


People just don't understand how dangerous this storm is..


Great statement! I totally agree.
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Quoting Gorty:
Looks like an east jog.


Your eyes must b crossed
Member Since: June 2, 2010 Posts: 0 Comments: 1338
irenes cdo is quickly evaporating
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HMMMMM....this is for all those who posted earlier... the President is cutting his vacations short...him and the entire family are leaving Martha's Vinyard today and returning to DC...and btw...it was on CNN just a few weeks ago...the current pres has taken less vacation days upto date than either of the Bush boys or Reagan...guess he does care
Member Since: September 16, 2007 Posts: 0 Comments: 3599
Quoting NoVaForecaster:
One thing I haven't seen yet on satellite imagery yet is low level outflow clouds which are indicative of weakening and dry air absorption.


(courtesy of P451s post)

IMO it will have about 4-12 hours to strengthen back to a borderline Cat 3 and then will weaken thereafter. Its just going through an EWRC right now and with its slow forward speed it has time to reform an eyewall and briefly strengthen over the Gulf Stream waters.



No matter what happens though it is still a major threat to the NE. Please, PLEASE listen to the authorities as they know best what to do.


People just don't understand how dangerous this storm is..
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Quoting UKHWatcher:


I think your wait is almost over....
,doubt it i live in sarasota and we dont get landfalling hurricanes here,let alone a major,we'vevneer had a major landfall here in sarasota!
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Quoting reedzone:
Everyone right now.. STOP THE DOWNCASTING!!! Irene is not falling apart, would love to see evidence, besides the water vapor, that Irene is rapidly weakening. You are mis informing the people who are trying to find out the reality of this storm. Irene will most likely be a Hurricane when it hits the Northeast, period!

no doubt! but still its not the monster it was looking like it was going to be last night. though still a VERY powerful storm and with most storms its size and given its former strength, its going to have a large storm surge! So treat it like it is a very serious storm Northeast!!!
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Quoting thedawnawakening3:
I won't be surprised if Irene intensifies quickly tonight up until landfall on NC. Also of note is that TD 10 could be a mix of pre Katrina 2005 TD 10 and Hurricane Wilma, in terms of Katrina's pre TD10 and the track into the Caribbean Sea like pre Wilma. Still a lot to watch out for in the coming weeks.


The doom casts will start again. I give it a week to 10 days.
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Quoting HurricaneHAM:


Where do you see this warning? I'm in Wake Forest/Raleigh and I'm seeing this on NWS--20 to 40mph wind.
Johnston County is under High Wind Warning. Wake County is NOT.
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looks liek a east jog looks like a west job looks like an easter egg... geesh it will be bad it wont be bad its this its that...
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a dry air "dagger" has been spiral of archimed-ing toward Irene's heart the past 60 minutes. see if it can strike at the core...

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Quoting P451:


Unfortunately good people always get lumped into the generalization. Without spending a time making a list of names which I find to be disrespectful - the generalization stands to make a decent point.

It's just the dynamic of the blog and an unfortunate one because some of those individuals who disappear are very good at forecasting these storms. So their input is lost.

I'm from NJ and presently in NY. I watch and talk about storms that hit anywhere in the basin. My interest is not based on whether or not it's a threat to my area.

For most on here, that is their primary reason for being a part of the blog, and when that threat passes, the storm is meaningless to them and not worth discussion.

That's a turnoff to me and if that hurts some feelings well...it happens.


Don't get me wrong I agree with the sentiment - I just think you'll find that there are far more people who do follow storms regardless of whether they are in the firing line (just more quietly). By generalizing you are inadvertently being more disrepectful to those people than the idiots who do try to claim that everything is going to hit and do not care about any but themselves (who are actually the one who deserve no respect as I agree it is extremely self-centered).

That said, we should actually be thankful that many of those are not posting today as their 'forecasts' would be taking Irene anywhere but where she is actually heading.
Member Since: August 31, 2010 Posts: 0 Comments: 90
751. Gorty
Looks like an east jog.
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Quoting TropicalAnalystwx13:


That is not true. Irene's structure continues to improve on satellite.


The Storm will bring heavy amounts of rain and some strong wind to a large area. Tropical storm conditions to most.
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Quoting DavidHOUTX:


Similar to what happened right after Ike made landfall? News outlets reported it for a day or two max then never heard about it again. Unless of course you were watching the Houston news.
So how sre things in Gulfport MS post Katrina?
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Quoting NoVaForecaster:
One thing I haven't seen yet on satellite imagery yet is low level outflow clouds which are indicative of weakening and dry air absorption.


(courtesy of P451s post)

IMO it will have about 4-12 hours to strengthen back to a borderline Cat 3 and then will weaken thereafter. Its just going through an EWRC right now and with its slow forward speed it has time to reform an eyewall and briefly strengthen over the Gulf Stream waters.



No matter what happens though it is still a major threat to the NE. Please, PLEASE listen to the authorities as they know best what to do.
100% agree
Member Since: September 22, 2005 Posts: 11 Comments: 2032
Quoting Vero1:
???it runs N and S / Cape May to NYC is the flow N-bound or S-bound?
I was wondering the same.
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Quoting Bluestorm5:
Right now, we are in High Wind Warning with gusts up to 60 MPH according to NWS Raleigh:

30 TO 40 MPH WITH PEAK GUSTS BETWEEN 50 AND 60 MPH.

And if Irene kept going to NNW for 2-3 more hours, then we'll get tropical storm warning. If this storm go all the way to Wilmington landfall (little chance), we'll get Hurricane Warning.


Where do you see this warning? I'm in Wake Forest/Raleigh and I'm seeing this on NWS--20 to 40mph wind.
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Quoting ConnecticutWXGuy:
So here's a question for you whiners about "oh the media over-hyped the storm."

What is better? over-hyping, or under-hyping? Because unless you can make perfect forecast without any chance of being wrong... one or the other is always going to happen. Do you suggest that the media takes the current forecasts and downplays them? Because as much as I disagree with a lot of what the media does, they certainly have not "up-played" this storm and its potential all that much at all.
If you broaden this discussion you can ask why some people are downplaying the threats from climate change. Better be safe than sorry! A hurricane will pass, climate change is persistent.
Member Since: September 22, 2005 Posts: 11 Comments: 2032
Quoting stillwaiting:
nyc is over reacting imo,it'll blow,but not like uptown,lol...shutting down the airports is normal for even a tropical storm though


I think your wait is almost over....
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Quoting TropicalAnalystwx13:


Didn't you hear? It's rapidly falling apart..
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739. Vero1
Quoting FLdewey:
The garden state parkway is going contra-flow tonight.

Now that I got to see.

*fist pump*
???it runs N and S / Cape May to NYC is the flow N-bound or S-bound?
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Lol the doom and gloom forecasts were hilarious on the weather channel this week. More than likely, Irene will be a classic sheared mess when it gets into the mid Atlantic region and northeast.
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Quoting reedzone:
Everyone right now.. STOP THE DOWNCASTING!!! Irene is not falling apart, would love to see evidence, besides the water vapor, that Irene is rapidly weakening. You are mis informing the people who are trying to find out the reality of this storm. Irene will most likely be a Hurricane when it hits the Northeast, period!


Relax Reed, there is a decent chance it will be a tropical storm as well per NHC intensity tables (in the NE). Just wait and see at this point.
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Quoting reedzone:
Everyone right now.. STOP THE DOWNCASTING!!! Irene is not falling apart, would love to see evidence, besides the water vapor, that Irene is rapidly weakening. You are mis informing the people who are trying to find out the reality of this storm. Irene will most likely be a Hurricane when it hits the Northeast, period!


Are you in denial often?
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Quoting 69Viking:


Whatever, .2 W is .2 W, call it what you want but it's not N.


apparently you think they should say NNW or NNE if the direction is even a fraction of a degree off of complete due north. But there is a guideline as to what direction is what.

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For people saying shift to 30 miles west or east... 30 miles make the landfall mark from Morehead City to Wilmington or out to OBX. Shift to Wilmington can creates massive flooding event in NC and minor wind damage all the way to Raleigh. This is big deal for North Carolina... people need to focus on New England AFTER we get hit first with 6-12 feet surge into our coastal cites in which most of them are not protected from Surge! Atlantic Beach and Beaufort is great examples of cities not being protected from the surge.
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Quoting reedzone:
Everyone right now.. STOP THE DOWNCASTING!!! Irene is not falling apart, would love to see evidence, besides the water vapor, that Irene is rapidly weakening. You are mis informing the people who are trying to find out the reality of this storm. Irene will most likely be a Hurricane when it hits the Northeast, period!

It is has stopped weakening at the moment, going over the Gulf Stream now, should see a flare up before it hits North Carolina, but the eyewall structure remains poor.
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nyc is over reacting imo,it'll blow,but not like uptown,lol...shutting down the airports is normal for even a tropical storm though
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Quoting Melagoo:


Irene will not be a Hurricane when she blows into NY City and the media hype will scare everyone except New Yorkers



Lol anyone else on earth is scared except new Yorkers. Like dr evil says "right"
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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.