Hurricane Irene Prepares to Leave the Bahamas and Head for the US

By: Dr. Jeff Masters , 7:51 AM GMT on August 25, 2011

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As of 2AM EDT, Hurricane Irene was located at 24.2N, 76.0W, 105 miles east-southeast of Nassau or 760 miles south of Cape Hatteras. It was moving northwest at 12 mph with maximum sustained winds of 115 mph, making it a Category 3 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 950 mb. Hurricane force winds can be found up to 70 miles from Irene's center, and tropical storm force winds can be found out to 255 miles from the storm's center.

Hurricane warnings are in effect for all of the Bahamas. Hurricane and tropical storm watches will likely be posted for the Carolina coastlines later this morning. At this time, Dare County Emergency Management has issued a mandatory evacuation order for all visitors in their county. Dare County Schools will also be closed Thursday and Friday.

Satellite Views
Figure 1 is the infrared satellite image of Irene at 135EDT. The convection is a bit unbalanced around the storm center, which is going to cause Irene to wobble like an unbalanced clothes washer (Analogy courtesy of Angela Fritz) over the next few hours. At the time this image was taken, the convection around Irene's center appears to be getting more vigorous, as cold cloudtops are starting to increase around the storm center. This is important to note because microwave satellite imagery from Wednesday evening suggested Irene was starting an eyewall replacement cycle. Figure 2 shows passive microwave imagery from a Air Force DMSP polar-orbiting satellite. The two concentric green/yellow bands in the image suggest that two eyewall features are present in Irene, and Hurricane Hunter observations confirm this. This has important consequences for Irene's intensity, because in an eyewall replacement cycle, as the inner eyewall weakens, the storm's intensity drops. However, once the inner eyewall is gone, and the outer eyewall contracts to replace it, the storm intensity will increase again.


Figure 1 IR satellite view of Irene taken at 113AM EDT, August 23, 2011


Figure 2 DMSP F18 microwave overpass of Irene at 824PM EDT, August 24, 2011. Image courtesy of the Naval Research Laboratory

Track Forecast

Irene is forecast to move to the northwest, passing over the northwest Bahamas by Thursday evening, then curving to the northeast. Irene then makes landfall in the US near or at the Outer Banks Saturday afternoon, then traveling along the mid-Atlantic coastline of the US. Sunday, Irene may make secondary landfall anywhere from New Jersey to Long Island and the southern New England coastline. In my opinion, New York City may be significantly impacted by Irene. It is also important to note that the windfield of Irene is expected to be large, affecting areas distant from the immediate track of Irene's center. Tropical storm forces winds are expected to be found out to at least 150 miles away from Irene's center on Friday afternoon.

NHC is forecasting for Irene to become a Category 4 storm (winds faster than 130 mph) by Thursday morning. As Irene moves northward into cooler water, the intensity is expected to drop slowly to a Category 2 storm before making landfall in the Outer Banks.


Figure 3 Official track forecast of Irene at 2AM EDT.

Forecast models and today's planned flights
The different forecast models are still in fairly good agreement about Irene's track through the Bahamas and along the east coast of the US. The 00Z GFS run is in close agreement with the 12Z ECMWF run, but the 00Z ECMWF run (shown in figure 4) is continuing the ECMWF's trend of shifting the track westward with each run. NHC forecasters have been placing emphasis on the ECMWF's forecast track when making their forecasts for IRene, so it is possible that the NHC track will shift westwards at the 5AM update.

Looking at the plan of the day valid for today, it will be a busy day for airborne reconnaissance. Three flights for the Air Force hurricane hunters, two flights for the Gulfstream IV (Gonzo), and two flights for NOAA 42, a WP-3D (Kermit). They may have to give NOAA a littering permit for all of the dropsondes used to monitor Irene and her environment, but the forecast improvements they generate are worth the effort.


Figure 4 Plot of the maximum sustained winds in mph over the next week from the 00Z ECMWF forecast.

Impacts

Hurricane force winds will arrive in the northwestern Bahamas today. Storm surge near the center of Irene will be 7-11 feet above tide level. The Bahamas can expect 6-12 inches of rain over the next day or so, and it looks like the Turks and Caicos islands will receive a total of 6-12 inches from Irene. Large, swells from Irene will start landing on the southeastern US coastline later today. Please don't go in the water, as these swells can cause dangerous rip currents. Dr. Masters has catalogued the worst-case storm surge surge scenarios as a function of storm intensity here.

In my opinion, people living from the Carolinas to Cape Cod should pay close attention to Irene and prepare for a wide range of impacts. I think that there is a 75% chance of Irene's secondary landfall will be somewhere between JFK airport and Cape Cod. That said, Irene's size will cause significant impacts for people living far from it's center.

Dr. Masters will have a new blog entry this morning, and Angela Fritz will be covering the afternoon. I'll be back on third shift tonight.

Thanks for reading,

Dr. Rob Carver

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I also want to remind people that even if you are in the tropical storm scenario, that could mean winds anywhere from 39mph to 73mph..
Member Since: August 19, 2006 Posts: 13 Comments: 14399
Irene doesnt look as good this morning. What happens( in reference to track) if in the next 12 to 24 hours the pressure stays the same or starts rising instead of dropping?
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Aisl--I am about 60 N of SC line--worst is to be to my N. NO evac orders ect---Been watching her for what seems like weeks now. I appreaciate your advice--I don't take chances either:-)
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Good Morning...
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Extremely intense 700 mb winds found 70+ miles out from Irene's center. This implies that once her EWRC is complete and she protects her inner core from dry air intrusion those winds will come down to the surface and she will strengthen pretty quickly.
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Quoting aislinnpaps:


LOL, I figured the coffee he needs is too strong, it might melt the straw.


LOL!!!

The stronger the better. TS Watch for the Charleston area.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
Wow Irene. Wonder if she can even gain that eye back. Could be a Cat 2 at 8:00.
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139. afj3
Insurance Expert on CNBC right now. He says sentiment as of now is damage (in monetary terms) may resemble Hurricane Floyd of 1999 and not as bad as an Andrew (1992) or--obviously--a Katrina. Anyone remember Floyd from 1999? Hope there's not too much damage. As much as I love storms, I'm afraid what one would do to the economy (double-dip recession?) although maybe it would be a boon for construction and serve as the stimulus the economy needs. Thoughts?
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Quoting aquak9:
hands Nash some coffee.

Thanks ais, I was just gonna give him the coffee-pot and a straw.


LOL, I figured the coffee he needs is too strong, it might melt the straw.
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Quoting StormJunkie:


Morning Nash, haven't checked the ECMWF; but the GFS has shifted slightly W. Not much, but enough to be pretty confident that the OBX are the furthest point E she will go. I would also still be a little nervous if I were in Wilmington. I doubt she'll end up any further W than that.


Agreed. Just did a quick check on the trough. Not as amplified as originally predicted. Where have we heard that before? LOL! But yeah. At this point, I don't see her going any further W than the NC/SC border at most. That trough would have to totally flatten out and lift out for her to make it to 80W IMO.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
Quoting 900MB:


The way I see it, Irene is just hitting her best water temps as it is crossing into an area of 30-31 degrees and should ride the gulf steam with temps in that range right up to the NC/VA border. Which is part of the reason that I don't understand the NHC's intensity forecast of a decline from 135 mph, fri at 2am (off Fla) to 115mph on Sat 2am (off GA/SC border).


shear is forecast to weaken her
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I will admit, the local coverage here in Eastern NC is....spotty right now. Being in NE NC, I get Eastern NC and Hampton Roads channels, and none thus far are getting hyped about the storm. The Weather Channel might have Abrams and Al Roker in Duck, but they still primarily focus on and talk about NJ/NY/RI and other points in the NE. It's like NC doesn't matter to anyone, not even the people who live here and are supposed to report on NC.

The westward shift in the models does make this a major concern for more than the OBX. I personally predict a landfall on the Emerald Isle, with it passing over Newport, Havelock, up to Belhaven, over Elizabeth City (where I be), right over Va Beach, and then back out to hug the Eastern Shore. I think the OBX is going to get the east side of the storm, make a few new inlets, definitely mess up some cottages, and all around do some damage. Call me a fearmonger or a doomcaster, but that's what it LOOKS LIKE right now.

That kind of path would do some major damage to Va Beach as well, and you'd think the local media would be a SMIDGE more concerned about that.
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Quoting CarolinaBeachGirl:
Yes, 8 blocks back---not in high flood area or for storm surger. Only expecting TS conditions here. I am well prepared--should things change--can head off the island. But very few do so here.


Personally, I would go take a small vacation inland. Rita wasn't supposed to hit here. By the time I got out of school, teaching, it was too late to evacuate. Storms can turn unexpectedly and if you're on an island...
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The NHC's intensity forecast for Irene as it passes Long Island is a TS. Seem likely?
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Quoting stoormfury:
IRENE APPEARS NOW TO BE MOVING BETWEEN WNW/NW, BAD SIGN FOR NC


Looks pretty NNW to me.
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hands Nash some coffee.

Thanks ais, I was just gonna give him the coffee-pot and a straw.
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IRENE APPEARS NOW TO BE MOVING BETWEEN WNW/NW, BAD SIGN FOR NC
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Yes, 8 blocks back---not in high flood area or for storm surger. Only expecting TS conditions here. I am well prepared--should things change--can head off the island. But very few do so here.
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hands Nash some coffee. Yes, it has. I'm afraid a lot of people aren't going to take Irene seriously.
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112kt. flight level winds in the NE quad. Also it looks like recon missed the center.
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Time: 10:31:30Z
Coordinates: 25.4167N 75.9833W
Acft. Static Air Press: 695.6 mb (~ 20.54 inHg)
Acft. Geopotential Hgt: 2,867 meters (~ 9,406 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 152° at 98 knots (From the SSE at ~ 112.7 mph)
Air Temp: 10.1°C* (~ 50.2°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 106 knots (~ 121.9 mph)
SFMR Peak (10s) Sfc. Wind: 88 knots (~ 101.2 mph)
SFMR Rain Rate: 19 mm/hr (~ 0.75 in/hr)
(*) Denotes suspect data
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Quoting nash28:
Morning all.
*yawn* Still waking...

What's this I hear about the ECMWF and GFS shifting W?

Need coffee.


Morning Nash, haven't checked the ECMWF; but the GFS has shifted slightly W. Not much, but enough to be pretty confident that the OBX are the furthest point E she will go. I would also still be a little nervous if I were in Wilmington. I doubt she'll end up any further W than that.
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Quoting CarolinaBeachGirl:
Okay--I do understand:-) Little too close for comfort here, but I am putting faith in what we are being told. I am 8 blocks back and have been lucky in the past. You stay safe as well!


yeah, I think this is going to catch a lot of people off guard..any little deviation in Irene coming in and wilmington will get smacked..
Member Since: August 19, 2006 Posts: 13 Comments: 14399
Quoting CarolinaBeachGirl:
Okay--I do understand:-) Little too close for comfort here, but I am putting faith in what we are being told. I am 8 blocks back and have been lucky in the past. You stay safe as well!


You are eight blocks from the beach?
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Member Since: August 19, 2006 Posts: 13 Comments: 14399
Okay--I do understand:-) Little too close for comfort here, but I am putting faith in what we are being told. I am 8 blocks back and have been lucky in the past. You stay safe as well!
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120. 900MB
Quoting atmosweather:


It's not just about water temperatures it's the fact that she will be encountering moderate to strong SW-erly shear as the shortwave trough moves into the Great Lakes region and amplifies as she moves N-ward. Hurricanes rarely maintain their strength while moving towards the OBX and the mid Atlantic no matter how warm the waters of the Gulf Stream are.


I see the SW shear that you are talking about, but that doesn't stop the NHC from projecting 135mph 24 hours from now. I'm just wondering why the drop of 20mph between 24-48 hours when most of the models have pressure dropping and higher winds at the 48 hour point?

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Thanks, Yonzabam. I hope our friends there are all doing all right.
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118. MahFL
Get the Darwin awards ready....

"where he said some longtime residents were insisting on riding it out instead of evacuating to higher ground".....

Member Since: June 9, 2004 Posts: 0 Comments: 3245
She sure is looking ugly. She looks like she needs more cosmetic surgery. Irene has a window of about another 36hrs or so to intensify. The ERC has really taken her hot looks away.

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Morning all.
*yawn* Still waking...

What's this I hear about the ECMWF and GFS shifting W?

Need coffee.
Member Since: July 11, 2005 Posts: 190 Comments: 16972

As damage reports rolled in from the southern Bahamas Wednesday, grim pictures emerged: a church wall blown out on Mayaguana Island, missing boats in the Turks and Caicos, roofing stripped from Crooked Island’s high school and government buildings, downed trees and lost power everywhere.

Extensive impact — even before communication lines largely crashed to isolated, sparsely populated places like Acklins Island, which the eye of the 120-mph storm struck dead center. And the battering had really only begun. At 11 p.m., the National Hurricane Center was forecasting the massive system to grow bigger and stronger as it continues to howl across the Bahamas on Thursday.

On Long Island, administrator Jordan Ritchie told ZNS, the Bahamas news channel, that gusts had hit 90 mph by the afternoon and the rain was so intense it was hard to see.

“The power is off, the water is off and conditions continue to deteriorate,’’ he said. “It’s extremely dangerous out there.’’

From Crooked Island, Rev. Donald Kerr pronounced the region "devastated" and said many residents shocked as they left shelters to return to gutted, roofless homes.

Irene’s destructive core was expected to skirt east of New Providence Island, where most of the Bahamas’ 300,000-plus population lives near Nassau. But Stephen Russell, director of the National Emergency Management Center was worried about low-lying isolated atolls like Acklins, where he said some longtime residents were insisting on riding it out instead of evacuating to higher ground.




Read more: http://www.miamiherald.com/2011/08/24/2374165/hurr icane-watch-for-north-carolina.html#ixzz1W2GCBkJ0
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Quoting CarolinaBeachGirl:
NCStorm, I thought you were over in Brunswick county. Just a TS watch --even for the beaches


no, I am back in wilmington now..leland wasnt for me:)
Member Since: August 19, 2006 Posts: 13 Comments: 14399
Long time lurker, just now joining. Local (Virginia Beach) media outlets not that concerend for the local area. We haven't had any significant tropical system since Isabel in 2003. She passed 70 miles west of VB as a TS. I'm afraid a lot of people around here are going to wake up Sunday morning and say "What happened?!?"
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Member Since: August 19, 2006 Posts: 13 Comments: 14399
111. beell
Quoting katadman:
G'morning,Beell and SJ. Haven't greeted either one of you in a couple of years. Good to see you, although it could be under better circumstances.


Hello, katadman. It has been a few. Better circumstances would probably find us all asleep right now.

Good to see you here this morning as well.
Member Since: September 11, 2007 Posts: 141 Comments: 16200
NCStorm, I thought you were over in Brunswick county. Just a TS watch --even for the beaches
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Very surprised even local news not concerned with Irene so close to FL. Freeport is only 215 mi from Orlando, Nassau is 344 mi; yet no concern despite size of storm? If (big if) Irene doesn't turn, might be too late to do anything? Only those talking and doing prep work are ones who live on the beaches. They have some faith, but err on side of caution.
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floyd was stronger something to watch in the carib.
Member Since: September 11, 2010 Posts: 1 Comments: 4313
Quoting 900MB:


The way I see it, Irene is just hitting her best water temps as it is crossing into an area of 30-31 degrees and should ride the gulf steam with temps in that range right up to the NC/VA border. Which is part of the reason that I don't understand the NHC's intensity forecast of a decline from 135 mph, fri at 2am (off Fla) to 115mph on Sat 2am (off GA/SC border).


It's not just about water temperatures it's the fact that she will be encountering moderate to strong SW-erly shear as the shortwave trough moves into the Great Lakes region and amplifies as she moves N-ward. Hurricanes rarely maintain their strength while moving towards the OBX and the mid Atlantic no matter how warm the waters of the Gulf Stream are.
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Bueno, I need to get a little shuteye. Goodnight, all. Stay safe!!
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Morning kata & CapeF

Robert - It is making a much more northerly motion than it has been, but there is certainly still some W component in there as well. I'd say NW to NNW for the most part and I would expect that to continue through the day. The 06z GFS is not showing any east component until early Sat am from what I can tell.
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104. 900MB
Quoting PaulinJax:
Wont Irene strenghten when she gets over the Gulf Stream ?


The way I see it, Irene is just hitting her best water temps as it is crossing into an area of 30-31 degrees and should ride the gulf steam with temps in that range right up to the NC/VA border. Which is part of the reason that I don't understand the NHC's intensity forecast of a decline from 135 mph, fri at 2am (off Fla) to 115mph on Sat 2am (off GA/SC border).
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I wake up and we are currently under a Hurricane watch and the models have shift back west..I dont see this as a outerbanks storm but a Eastern NC storm..I understand also that the trough is not going to be as strong as predicted earlier eithier..
Member Since: August 19, 2006 Posts: 13 Comments: 14399
gm SJ...guess we might get a little breeze up here. I didn't expect much, but Ive got the generator ready and gas cans full. It seems like Floyd was supposed to not here, as well. Guess we'll see.
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101. MahFL
Quoting 900MB:
The other problem I have with NHC forecast is that it has the storm peaking at 135mph at 2am Friday off the Florida coast and down to 115mph by Sat 2am just south of South Carolina. I don't see what happens between those 2 points to deteriorate the storm???


Shear and cooler/shallower water.
Member Since: June 9, 2004 Posts: 0 Comments: 3245
TWC just showed some of the wind and trees down in the Bahamas.
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She is not looking too well this morning. Her EWRC has been taking a long time. Most canes will not recover very well with these long cycles. Rita is a good example.
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Quoting katadman:


If I remember correctly, Dr. Master's has said several times over the years that the models and the NHC margin of error forecasting intensity is much greater than their margin for error in track.


They tend to underestmate intensity. Probably don't want to be accused of being alarmist.
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Notice the shape of Irene in the last few frames. She is already starting to take that northern turn Link
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G'morning,Beell and SJ. Haven't greeted either one of you in a couple of years. Good to see you, although it could be under better circumstances.
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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.