Hurricane Irene Approaches the Bahamas

By: Dr. Jeff Masters , 7:42 AM GMT on August 24, 2011

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As of 2AM EDT, Hurricane Irene was located at 21.3N, 72.6W, 400 miles southeast of Nassau. It was moving west-northwest at 9 mph with maximum sustained winds of 100 mph, making it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 966 mb. Hurricane warnings have been issued for all of the Bahamas and the Turks and Caicos Islands. Tropical storm warnings are in effect for Haiti from Le Mole St. Nicholas to the Dominican Republic border.

Satellite Views
Figure 1 shows that Irene has a large eye visible in infrared imagery, (26 miles across accoring to a report from the Hurricane Hunters at 130AM) with well-defined outflow cirrus bands. Tuesday evening, TRMM, NASA's tropical research satellite, flew directly overhead Irene, getting a radar scan of the storm using it's downward pointing radar, shown in Figure 2. It is immediately apparent that Irene has well-developed bands of rain showers, with strong storms present in the eyewall.


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


Figure 2 TRMM radar overpass of Irene at 713PM EDT, August 22, 2011. Image courtesy of the Naval Research Laboratory

Track Forecast

Irene is forecast to move to the northwest, passing over all of the Bahamas by Thursday evening, then curving to the north. 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. After Saturday, Irene may pose a threat to Long Island and the New England coastline. However, NHC is quick to remind us that the average forecast error for day 4 is 200 miles, so don't stop your hurricane preparations if you aren't in the immediate area of landfall. 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 major hurricane (winds faster than 110 mph), within 24 hours.


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

Forecast models and adaptive observations
The different forecast models are in fairly good agreement about Irene's track through the Bahamas and along the east coast of the US. The GFDL, a dynamical hurricane forecasting model, which had been a western outlier from the other models is now agreeing with them. When a set of weather models using slighly different initial views of the atmosphere and slightly different ways of simulating how the atmosphere works all agree on a forecast, then meteorlogists tend to believe that the forecast is more likely to occur. The 00Z GFS and ECMWF (wind swath shown in Figure 4) forecasts are nearly identical, which furthur boosts forecaster confidence.

In the 11PM forecast discussion, the NHC forecaster praises the NOAA Gulfstream IV (aka Gonzo) for providing infomation about the atmosphere around Irene that will influence it's track. 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, and two flights for NOAA 42, a WP-3D (aka Kermit).


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

Impacts

In the immediate future, Irene will have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are ongoing over the Turks and Caicos islands and southeastern Bahamas. These locations can expect storm surges that are 5-8 feet above tide levels. The northwestern Bahamas can expect hurricane force winds Thursday, and storm surges that are 7-11 feet above tide levels. The Turks and Caicos islands and all of the Bahamas can expect 6-12 inches of rain over the next two days.

I still think people living along the east coast of the US should closely monitor Irene and review their hurricane preparations. Irene will be a large storm, impacting areas far from the storm center track.

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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Quoting CoopsWife:
Oops - morning all.

Coffee, juice on the sideboard.

Today's menu -

Pan seared tenderloin, eggs (scrambled are on the sideboard already), home fried potatoes with a little sauteed vidalia onion, and biscuits with jelly...




I'm having some leftover gumbo, conebread, anna glass uh milk. But yours sounds purty good to.
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Quoting CoopsWife:
Oops - morning all.

Coffee, juice on the sideboard.

Today's menu -

Pan seared tenderloin, eggs (scrambled are on the sideboard already), home fried potatoes with a little sauteed vidalia onion, and biscuits with jelly...




Mornin Maam....Thanks....the donuts were getting a little stale!!
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Amen to that, SJ - the other day I was on the 'dirty side' of her - and that wasn't a pleasant thought.
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Oops - morning all.

Coffee, juice on the sideboard.

Today's menu -

Pan seared tenderloin, eggs (scrambled are on the sideboard already), home fried potatoes with a little sauteed vidalia onion, and biscuits with jelly...


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Morning CW :)

At least it doesn't look like it will be west of you!
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Thank you the clarification.
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It's looking like today's the day Irene
a) gets clear of both Hispaniola and Cuba,
b) establishes decent outflow in the western semicircle,
c)gets the morning crud out of her eye,
and consequently
d) throws down some RI.

I'll be surprised if there isn't at least one supplementary advisory in the next 24 hours.
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Morning Storm Junkie.

Latest forecast takes her about 60 miles due east of me at 96 hours as she heads up the coast. Grrr - well, I suppose I will just keep right on bringing the missiles inside. :)
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Quoting foggymyst:
Good morning. Just reading posts and I am kind of confused. Are the models trending back some? Thanks.


Nope, as of now it looks like the NHC & the models have a pretty good handle on Irene. She should move through the Bahamas, and then start turning NNE passing just of shore of the OBX.

Morning all
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Quoting foggymyst:
Good morning. Just reading posts and I am kind of confused. Are the models trending back some? Thanks.


No the track philosophy remains the same amongst the models and from the NHC.
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Good morning. Just reading posts and I am kind of confused. Are the models trending back some? Thanks.
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Quoting TomTaylor:
yes, the eye is still having some issues clearing out.

Cloud tops also warmed slightly one the most recent satellite imagery. Dvorak estimates reflect this too.

Anyway, I'm out as well. Later all


Night Tom...I should be hitting the hay before my 8 hour shift begins at noon but I just need to see this first RECON center fix lol.
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time for Miami to activate its defensive shield network.
Member Since: August 27, 2005 Posts: 0 Comments: 686
Quoting FLPandhandleJG:


With this new image.. hmm looks ragged to me but in the eye tho.. not there yet but trying to get her act together.. but im going to bed.. no more fun time for me.. night every1
yes, the eye is still having some issues clearing out.

Cloud tops also warmed slightly one the most recent satellite imagery. Dvorak estimates reflect this too.

Anyway, I'm out as well. Later all
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Quoting atmosweather:
Crooked Island is going to get smashed later today by a strengthening Category 3 or even Category 4 hurricane. Prayers and all possible luck go out to those folks. They will take a massive beating.


Crooked Island looks to take a direct hit today. And from the looks of it, Irene is about to undergo a Rapid Intensification.. Her eye is tightening up. Solid and intense convection is wrapped all the way around the center. I don't see anything stopping her except for some southwesterly shear.

Long Island will be next on her path, but the island should be on the western side of the eyewall, which hopefully will lessen the blow.

Cat Island could be on the east side of the eyewall which will certainly be devastating.

Eleuthera and Great Abaco will likely take a direct hit. Together they have a population of about 25,000 people. I expect that there will be major damage to the islands.

So basically every island along the eastern side of the Bahamas will be impacted. The only saving grace will be that the most populated islands; Grand Bahama, Nassau and Andros Island will be spared a direct hit.. Unless there is an unlikely and unexpected westward jog. I wish there were good news for the Bahamas but this is looking very depressing..
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With this new image.. hmm looks ragged to me but in the eye tho.. not there yet but trying to get her act together.. but im going to bed.. no more fun time for me.. night every1
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Quoting FLPandhandleJG:


I think we also might want to watch the wave that just got off the coast of Africa as well but still mainly stay with Irene at the moment..











i see an area of deep red and red violet near my country....
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I think we also might want to watch the wave that just got off the coast of Africa as well but still mainly stay with Irene at the moment..










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Quoting breald:
Anyone see Ike lately? I haven't seen him post.


I normally lurk, but I was wondering where he was, too
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Quoting NICycloneChaser:
Irene is properly going for it this morning. Wouldn't be suprised if HH found 950mb pressure.


Surely that is possible. Weird how the GFS just started it's run with Irene as a 990 MB hurricane. Instead of an almost 960 MB hurricane like it is now. Screw the computer models lol
Member Since: September 2, 2008 Posts: 0 Comments: 744
this place is much more sane at night, especially after the latest forecasts send the storm mostly out to sea...
Member Since: August 27, 2005 Posts: 0 Comments: 686
Irene is properly going for it this morning. Wouldn't be suprised if HH found 950mb pressure.
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Anyone see Ike lately? I haven't seen him post.
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Atlantic ridge continues to push westward, as reflected in the latest pressure maps, and info from the dropsondes. More of a push westward, closer to FL expected as reflected in the latest UKMET model.




At 03Z:



At 06Z:



Current at 09Z:
Member Since: September 2, 2008 Posts: 0 Comments: 744
this must be how the Bahama's feel about this blog..

http://www.theonion.com/video/hurricane-bound-for -texas-slowed-by-large-land-mas,14262/




Hurricane Bound For Texas Slowed By Large Land Mass To The South
Member Since: August 27, 2005 Posts: 0 Comments: 686
Irene has her make-up on today....
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I would suggest that the HHs might find a 950mb 120mph category three Hurricane Irene.
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satellite imagery as of 915z suggests convection has decayed somewhat on the southern side of her circulation, could be a temporary thing as she continues to gain better outflow on the western semicircle.
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Quoting Vincent4989:
1.at the next TWO (or special outlook if there is), what will Irene become?
a.Major
b.Still Cat 2
c.(for downcasters) cat 1 or less
2.What Irene's strength will be at landfall?
a. Td
b. Ts
c. Cat 1
d. Cat 2
e. Cat 3 or higher
(bold letters are my choice)
A/D
Member Since: August 11, 2010 Posts: 0 Comments: 784
1.at the next TWO (or special outlook if there is), what will Irene become?
a.Major
b.Still Cat 2
c.(for downcasters) cat 1 or less
2.What Irene's strength will be at landfall?
a. Td
b. Ts
c. Cat 1
d. Cat 2
e. Cat 3 or higher
(bold letters are my choice)
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She needs to begin to establish a southern outflow channel, otherwise her deepening could be limited. However convection is expanding in the western semicircle. Time will tell whether or not she is a category three or four and see if satellite intensity estimations are accurate when an eye becomes visible.
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Atlantic ridge continues to push westward, as reflected in latest pressure maps, and info from the dropsondes. More of push westward, closer to FL expected as reflected in the latest ECMWF model.


At 03Z:



At 06Z:



Current at 09Z:
Member Since: September 2, 2008 Posts: 0 Comments: 744
Quoting NICycloneChaser:


Fear not; They are on their way. Both of them.

They could not get there sooner lol
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Quoting FLPandhandleJG:


Yikes!!!


Absolutely spectacular...but so so so worried for the islands in the Bahamas in her path.
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Satellite based estimates continue to climb. Raw ADT number now has her at a cat 4.

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Quoting FLPandhandleJG:


Yikes!!!


Kinda reminds me of my ex-wife. She was a mean one eyed b--ch as well.
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Can't wait to see her in the sun!!
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Irene is starting to take on the pinwheel look, classic major hurrican presentation.
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Quoting atmosweather:


Those infrared satellite images depict a pretty classic major hurricane...extraordinary presentation.
yes indeed
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Quoting FLPandhandleJG:


Yikes!!!


Monster!!
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She is beginning to gain that special appearance on satellite imagery, that appearance that everyone knows about when a hurricane is about to take off in RI, well she's got that appearance. Outflow is beginning to take shape to her western semicircle.
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Yikes!!!
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Outflow is no longer being restricted on the western semi circle. Latest imagery suggests outfow should continue to expand with the next few images. She is intensifying rapidly in my opinion. Could be extremely serious situation for the central and northern Bahamas. She could be a category four later today.
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Quoting TomTaylor:
Irene's core of convection is looking more symmetrical than it ever has. Now we just need the eye to clear out



Those infrared satellite images depict a pretty classic major hurricane...extraordinary presentation.
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Crooked Island is going to get smashed later today by a strengthening Category 3 or even Category 4 hurricane. Prayers and all possible luck go out to those folks. They will take a massive beating.
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Irene's core of convection is looking more symmetrical than it ever has. Now we just need the eye to clear out

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Quoting TomTaylor:
Yeah, I agree. The models shift around a lot. Given the current forecast track, which calls for Irene heading near parallel to the east coast, a slight shift in track would make all the difference between landfall and no landfall.

I honestly don't like the idea of pinpointing landfalls. For people who like to do it, or are confident enough to do it, then fine go ahead but personally I see no point. For one it can be greatly misleading to the rest of the people reading your forecast (i.e. person thinking they're out of the woods when they aren't). Second, it is usually not noticeably better than the model consensus or NHC track. Sometimes you can tell that ahead of time that the model consensus will need to shift in one direction, but it's often not very significant.

Given the potential to mislead people and the fact that there is often not much of a reason to significantly disagree with the model consensus, I really see no point in pinpointing landfalls. I prefer to just point out general areas.


agreed. It doesn't take much actual path deviance from a forecast point to disrupt what the models may be showing as a landfall area 5 days down the road. Ergo I believe it's not a good Idea to attempt to "pinpoint". Although the models "usually" have a good handle on what's happening up to about 48 hours, but still better to keep it in an area and not try to give an exact point of where the storm will be IMO.
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Quoting atmosweather:


She is most likely a Category 3 hurricane at this point, but with no HH plane sampling the winds and few surface and buoy observations close to the center it's difficult for the NHC to make that call. I'm definitely interested in the first center fix by the next RECON aircraft at 8AM because I believe she has intensified pretty considerably.


Fear not; They are on their way. Both of them.

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ASCAT pass from 7hrs ago caught Irene

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Quoting drg0dOwnCountry:

:D

Give me Worcestershire sauce for my chicken!
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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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