Hurricane Irene Approaches the Bahamas

By: Dr. Jeff Masters , 07:42 GMT 24. Srpen 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 drg0dOwnCountry:

:D

Give me Worcestershire sauce for my chicken!
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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.
Agreed.

Pressures were low enough while recon was in the storm to support a weak cat 3 hurricane (mid 960s). Winds will eventually catch up to the pressure, and from satellite imagery it looks like the storm has continued to intensify (so pressures should be even lower).
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Quoting HimacaneBrees:


yeah you right!!!!


But as far as crow goes In the words of Rodney Carrington, I like it like I like my chicken with a little bit of fat on the end.. hehehehe

:D
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Quoting Stormchaser2007:
Raw T has it at a 7.0

2011AUG24 081500 6.6 933.0/ +0.8 /129.6 6.6 6.9 7.0


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.
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Quoting emguy:


Those words right there are the famous last words of a crow eating champ. Do you like yours smoked, rotisserie, fried, flame broiled, or baked with a light mango salsa? Let me know. Made to order, have it your way, it will be ready. LOL ;)


yeah you right!!!!


But as far as crow goes In the words of Rodney Carrington, I like it like I like my chicken with a little bit of fat on the end.. hehehehe
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Quoting HimacaneBrees:


Yeah was just trying to lighten folks up some. Only time will really tell what Irene really will do. I honestly believe with the current setup it's an east coast hit. But things can and will change. So I just go with it as it comes. I don't put much stock in models more than 2 to 2.5 days out.
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.
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Quoting alvarig1263:


Should be...


thanks, I am trying to figure out if any changes in track or other factors that occur in the 3 hours between the model runs and the official forecast influence the NHC's forecast. I know that didnt make since
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Quoting StarnzMet:
Wow further east like I said. Don't like to brag but who called it. Goodbye west track!


Those words right there are the famous last words of a crow eating champ. Do you like yours smoked, rotisserie, fried, flame broiled, or baked with a light mango salsa? Let me know. Made to order, have it your way, it will be ready. LOL ;)
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Quoting TomTaylor:
Advanced Dvorak Technique has Irene as a major hurricane already

CI# /Pressure/ Vmax
6.1 / 940.7mb/117.4kt
That's crazy!
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Quoting Vincent4989:
DOOMCon Warning: Doomcon level raised to moderate


OH CRAP!!!!! what do we do now boss?
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DOOMCon Warning: Doomcon level raised to moderate
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Quoting atmosweather:


Yeah I saw you reworded what you were saying so you are correct in what you mean lol.

Pine Cay
on North Caicos island is reporting 60 mph sustained winds about 60 miles ENE of the center of Irene.
Yeah I just removed the whole sentence from the original post.

Payed a little too much attention to Irene's short term movement and didn't realize it was just a momentary wobble. Ah well, learn something new everyday
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Quoting PELSPROG:


Flying iguanas reported on Great Inagua Is. as Irene's eyewall passes just east of the Island.


lmfao!!
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Quoting FLWaterFront: And to be honest, there is at least a 1 in 100 chance that they could actually be right. But if not, I hope they will remember Irene for the next time a storm is forecast to go somewhere else besides Florida, and lay off the Florida wishcasting.
What are the odds? For me it is over when the northward turn becomes clearly visible, so far that is not the case :)

An Hebert Box (pronounced AY-bear, also known as Hebert's Box) is one of two regions of the tropical Atlantic Ocean that are useful as predictors of hurricanes that will strike South Florida, USA. They are named for former National Weather Service and National Hurricane Center forecaster Paul Hebert, who observed in the late 1970s that most strong hurricanes (characterized as those with winds exceeding 110 miles per hour (177 km/h)) which had struck South Florida since 1900 had also passed through one of these two small 335-mile-by-335-mile (517-km-by-517-km) square geographic regions. http://en.wikipedia.org/wiki/Hebert_box
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The East Coast will take quite a beating from Hatteras Northward. And The Carolinas are not out of the woods yet . Irene will get it's name retired when all is said and done.
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***CARRIED OVER FROM LAST BOARD***

Ok, kids the Ambien just kicked in so this is the last one I'll be able to put together till later.

Don't forget the meeting tonight on Cat Isl. - you may
want to bring an umbrella......and a SQUEEGEE! ;-)

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Quoting TomTaylor:
Yea it is pretty calm tonight.

As far as the east/west argument, there really isn't one. People, including myself, have just been looking at the satellite too much and are mistaking wobbles for the overall path of the storm.


Yeah was just trying to lighten folks up some. Only time will really tell what Irene really will do. I honestly believe with the current setup it's an east coast hit. But things can and will change. So I just go with it as it comes. I don't put much stock in models more than 2 to 2.5 days out.
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Latest microwave pass (from 6:21 UTC/ 2:21 EDT - about two and a half hours old)

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Quoting NCCANE:
the current models are the 0600z runs correct?


Should be...
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Kermit is back in the air.

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the current models are the 0600z runs correct?
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Quoting HimacaneBrees:
Boy for a borderline major hurricane out there, the blog is quite slow. I love reading the east/ west arguments. It's better than the old soap opera's like that one uhh "the young and the useless" or something like that.
Yea it is pretty calm tonight.

As far as the east/west argument, there really isn't one. People, including myself, have just been looking at the satellite too much and are mistaking wobbles for the overall path of the storm.
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Quoting alvarig1263:


Only went further east cause other models haven't ran yet. Just wait till the 11AM... ;-)


Yeah I think the models are throwing the NHC off to far. I know models can show some reliance generally but they always can not be trusted for forecasting. I think the facts might speak for itself if Irene does not start heading NW here soon. Expect this storm to track back in on a more westward path. Its just not a feeling I have but I am looking at all the maps and it certainly does not indicate a more easterly track is possible as of now. I think its safe to say the possibility this goes further west is not out of the picture.
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Boy for a borderline major hurricane out there, the blog is quite slow. I love reading the east/ west arguments. It's better than the old soap opera's like that one uhh "the young and the useless" or something like that.
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Quoting alvarig1263:


Only went further east cause other models haven't ran yet. Just wait till the 11AM... ;-)


"THE DYNAMICAL TRACK MODEL CONSENSUS
HAS...AGAIN...SHIFTED A LITTLE TO THE EAST FROM THE PREVIOUS
PACKAGE. THE OFFICIAL FORECAST IS NOT SUBSTANTIALLY DIFFERENT FROM
THE PREVIOUS ONE AND LIES A LITTLE TO THE LEFT OF THE CONSENSUS."
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Quoting EastTexJake:
If you look at the track of Irene from when she was first named on 8-20. You can draw a line from that point to her last plotted location, her course has not deviated from that line very much at all. Irene has waddle along the same line for almost five days now.


only updates every 6hours
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Quoting StarnzMet:
Wow further east like I said. Don't like to brag but who called it. Goodbye west track!


Only went further east cause other models haven't ran yet. Just wait till the 11AM... ;-)
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Wow further east like I said. Don't like to brag but who called it. Goodbye west track!
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Raw T has it at a 7.0

2011AUG24 081500 6.6 933.0/ +0.8 /129.6 6.6 6.9 7.0
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BULLETIN
HURRICANE IRENE ADVISORY NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 AM EDT WED AUG 24 2011

...IRENE CONTINUES TO STRENGTHEN AS IT POUNDS THE SOUTHEASTERN
BAHAMAS...WILL LIKELY BECOME A MAJOR HURRICANE LATER TODAY...



SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...21.6N 72.9W
ABOUT 370 MI...595 KM SE OF NASSAU
ABOUT 955 MI...1535 KM S OF CAPE HATTERAS NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...962 MB...28.41 INCHES
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Quoting TomTaylor:
But they did adjust the start position of the track.

Point was at 11pm she was west of the track. At 2am they centered the start point over her current location, and Irene is now following the projected path.

I guess if you want to get technical...had they kept the 11am track still there, she would be back inline with the forecast track, but whatever.


Yeah I saw you reworded what you were saying so you are correct in what you mean lol.

Pine Cay
on North Caicos island is reporting 60 mph sustained winds about 60 miles ENE of the center of Irene.
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Further east we go.

Amazing.

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PELSPROG,
Best I've heard all day
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Advanced Dvorak Technique has Irene as a major hurricane already

CI# /Pressure/ Vmax
6.1 / 940.7mb/117.4kt
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5 am is way east
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Quoting invisidog:
Does anyone have reports of wild animal movement along the projected landfall path? We saw significant animal/reptile movement starting 3 or 4 days out in areas that recieved major tidal surge. This occurred just prior to Hurricane Hugo.


Flying iguanas reported on Great Inagua Is. as Irene's eyewall passes just east of the Island.
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Quoting StarnzMet:
Nothing about a Florida impact! Put that pipe dream to bed wishcasters!!! Thank you Dr. Carver
Yeah, this Florida wishcasting thing is amusing sometimes, but it also gets old.

What those who practice this art apparently fail to realize is their attempt to look unbiased and objective is transparent. Notice how they don't wishcast for SC, GA, or most anywhere else nearly so often?

But when a storm is anywhere on a path that moves it even remotely close to Florida, then every Upper Level Low, every real or imagine high pressure dome, every confirmed or rumored river of air in the atmosphere becomes the veritable proof that the entire global tropical cyclone forecasting system has crashed spectacularly and it's "Florida here we come!" for whatever TC is on the map.

I know that a lot of these people are sincere in their belief that Irene will surely bypass all of the computer models, the NHC and all of the other expert meteorologists working on this system 24/7 and make an "unexpected" lunge directly at Florida. And to be honest, there is at least a 1 in 100 chance that they could actually be right. But if not, I hope they will remember Irene for the next time a storm is forecast to go somewhere else besides Florida, and lay off the Florida wishcasting.
Member Since: 15-10-10 Posts: 0 Comments: 753
For those that say she is west of the track I recommend glasses, or better glasses. I'm out looking more and more like a full recurve. peace
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Quoting hyperanthony:
Pulled the latest shot from the rainbow floater... click to enlarge.



Source: http://www.ssd.noaa.gov/goes/flt/t2/flash-rb.html
Core still lopsided, but it is looking better than before. Eye is also clearing out better.

I want to go to bed but Irene is keeping me here lol
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If you look at the track of Irene from when she was first named on 8-20. You can draw a line from that point to her last plotted location, her course has not deviated from that line very much at all. Irene has waddle along the same line for almost five days now.
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Quoting emguy:
She probably remains just a smidge west of track. The portion of the eye we are seeing is the NE corner...for three reasons...A.) Angle os satellite, which is over equator. B.) She is slightly tilted NE with altitude. C.) and most importantly, she has a lot of overshooting cloud tops on the W, SW, and S side obscuring the eye further.


I agree. she has been corkscrewing for the last 12 hours or more and appears to be west of forecast.
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Pulled the latest shot from the rainbow floater... click to enlarge.



Source: http://www.ssd.noaa.gov/goes/flt/t2/flash-rb.html
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Latest satellite imagery puts Irene right over the NHC's track forecast, or possibly just slightly east of it since the track isn't a straight line, it's a curve.

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Quoting emguy:
She probably remains just a smidge west of track. The portion of the eye we are seeing is the NE corner...for three reasons...A.) Angle os satellite, which is over equator. B.) She is slightly tilted NE with altitude. C.) and most importantly, she has a lot of overshooting cloud tops on the W, SW, and S side obscuring the eye further.


if anything she is a tad east of the track but looks pretty close right now
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She probably remains just a smidge west of track. The portion of the eye we are seeing is the NE corner...for three reasons...A.) Angle os satellite, which is over equator. B.) She is slightly tilted NE with altitude. C.) and most importantly, she has a lot of overshooting cloud tops on the W, SW, and S side obscuring the eye further.
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Does anyone have reports of wild animal movement along the projected landfall path? We saw significant animal/reptile movement starting 3 or 4 days out in areas that recieved major tidal surge. This occurred just prior to Hurricane Hugo.
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Quoting atmosweather:


They did not adjust it at 2AM. Only times when the track is updated is 03/09/15/21z at the complete advisories unless there is a special advisory package.
But they did adjust the start position of the track.

Point was at 11pm she was west of the track. At 2am they centered the start point over her current location, and Irene is now following the projected path.

I guess if you want to get technical...had they kept the 11am track still there, she would be back inline with the forecast track, but whatever.
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Thanks Dr. Carver! Hoping for safety to the people being impacted by the storm today.
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Quoting TomTaylor:
I was speaking about the 11PM track.

That is the 2 AM track. The NHC had to adjust their track.


They did not adjust it at 2AM. Only times when the track is updated is 03/09/15/21z at the complete advisories unless there is a special advisory package.
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Quoting winter123:
Irene is right on track, actually.
I was speaking about the 11PM track which she was slightly west of.

That is the 2 AM track.
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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.