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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Recon headed into the NE eyewall.
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Quoting Orcasystems:


Plywood


LOL!!
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Gonzo is making a Vortex run



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Quoting FSUstormnut:

would you mind posting the link to this? thanks


Link
Member Since: August 1, 2007 Posts: 0 Comments: 179
Looks like its heading right for WPB, sure hope it makes that turn over the bahamas even so south florida is going to feel the wind
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06Z HWRF 108 hours





HOUR: 108.0 LONG: -73.10 LAT: 40.40 MIN PRESS (hPa): 930.00 MAX SURF WIND (KNOTS): 87.00
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Quoting CaneHunter031472:
ECMWF 00z T=72hrs

would you mind posting the link to this? thanks
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Quoting TampaSpin:



Pretty Narrow opening currently........WOW


Definately narrow, looks like that shortwave over the great lakes should nudge it just like the models are predicting. Hopefully enough to clear the coast a bit more then anticipated and just a brushing up the eastern seaboard.
Member Since: August 21, 2007 Posts: 0 Comments: 211
surf beginning to roll in starting at a 11 second swell. speaking of big swells look at tahiti's forecast 20sec!
Member Since: September 11, 2010 Posts: 1 Comments: 4587
Quoting ncstorm:
The ECWMF ensembles are showing a western track..

Noticing a jog to the left with Irene for the moment. Every little jog like this from now on will make a difference in making landfall for N/S Carolina or not. She should be starting to turn more to the NW today.
Member Since: June 13, 2009 Posts: 0 Comments: 6775
Baha,stay safe and report to us what is going on there when you can.
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Now folks this is what you call Convergence......something we have not had much of from any storm this year except now.
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IMO it looks like next update it will be moving nw..
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ECMWF 00z T=72hrs
Member Since: August 1, 2007 Posts: 0 Comments: 179
NOAA dropsonde in the eye


957mb (Surface) 175° (from the S) 3 knots (3 mph)
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Quoting TampaSpin:



CAT1 for NY City........at that angle won't be good.....


I agree. A hit at that angle will mercilessly pile water into Narragansett Bay.

31 flavors of ugly…

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Gotta love the end of the Houston are forecast discussion this morning if you are any kind of Star Wars fan.

"BUT OVERALL NOT A LOT OF NEW HOPE ON THE HORIZON AS THIS
TATOOINE-LIKE CLIMATE PERSISTS. 41"
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261. GoWVU
Quoting WxLogic:
Should hopefully be updating in 30min to 1HR... but latest steering for Irene:



Would yield a WNW to NW (at times).


If the currents dont change, does that open the door for the SE? please explain the map, thanks
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i really doubt irene wont make landfall in north carolina with its wobbles to the west and its motion still wnw it will most likely make landfall then go through new england. you guys think a cat 3 is possible at the 8am advisory?
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Quoting Tazmanian:



when the storm gets ready too


Thanks for the insight
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Quoting aquart:
I lurk, being vastly ignorant and preferring to learn...but am I correct in assuming that my stable temperate zone Manhattan is going to have an earthquake and a hurricane IN THE SAME WEEK?

I have old brownstone seven-foot windows. Tape them? With what?


Plywood
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Here is a link to cuba radar:

http://www.insmet.cu/asp/genesis.asp?TB0=PLANTILL AS&TB1=RADAR&TB2=../Radar/06Gran%20Piedra/gpdMAXw0 1a.gif

Cuba Radar

The link posted yesterday was a mosaic of 6 radars, but you see the banding much better if you just look at the view of the easternmost radar in Gran Piedra.
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PR has seen epic rainfall from Irene and it's tail. So far between 15-20 inches has fallen here.

CLIMATE...IMPRESSIVE RAINFALL TOTALS PAST FEW DAYS HAS RESULTED
IN NEW RAINFALL RECORDS BEING BROKEN AT THE LMM SJU INTL ARPT.

SO FAR THIS MONTH...A TOTAL OF 16.53 INCHES OF RAIN HAVE BEEN
MEASURED. AUG 2011 IS NOW THE WETTEST AUG ON RECORD BREAKING THE
OLD RECORD OF 14.10 SET BACK IN 1944. AUG 2011 IS ALSO THE THIRD
WETTEST MONTH OF ANY YEAR ON RECORD SINCE RECORD KEEPING BEGAN IN
1898. ONLY 0.35 INCHES OF RAIN NEEDED TO BREAK THE RECORD OF 16.88
INCHES MEASURED BACK IN MAY 1936. WITH STILL EIGHT DAYS LEFT THIS
MONTH IT IS PRETTY MUCH DEFINITE THAT THIS RECORD WILL BE BROKEN
BEFORE THE MONTH IS OVER. LASTLY...AN INCREDIBLE 61.07 INCHES OF
RAIN HAVE ALREADY BEEN MEASURED SO FAR THIS YEAR. THIS REPRESENTS
THE WETTEST START TO A YEAR ON RECORD WELL AHEAD OF 2010 WHEN
52.89 INCHES HAD BEEN MEASURED TO THE DATE.

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Boston is gonna get hammered as well.....
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104 snotly "this must be how the Bahama's feel about this blog...
Hurricane Bound For Texas Slowed By Large Land Mass To The South
"

As noted in an earlier blog, Texas is still in play.
Extending the straightline projection from my latest mapping (for 24August_6amGMT)...

...Irene was headed for KingRanch,Texas -- which amongst other virtues has the lowest population density of any county within hurricane territory. Everybody living there could stand a mile apart from each other, and they still wouldn't cover the entire county.

Copy&paste 20.1n69.7w-20.4n70.6w, 20.4n70.6w-20.7n71.2w, 20.7n71.2w-21.1n71.9w, 21.1n71.9w-21.3n72.5w, iga, dct, 21.1n71.9w-22.36n75.81w, mrk, 21.1n71.9w-27.2n97.44w, kbks into the GreatCircleMapper for more info
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nevermind I am not sure what I was looking at must have been an old image ... the storm definately is increasing convection... now if it can only get a well defined clear eye now we will see this thing jump to cat 4
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252. Vero1
Quoting aquart:
I lurk, being vastly ignorant and preferring to learn...but am I correct in assuming that my stable temperate zone Manhattan is going to have an earthquake and a hurricane IN THE SAME WEEK?

I have old brownstone seven-foot windows. Tape them? With what?
Tapeing windows ONLY helps picking up the glass pieces.
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Quoting TampaSpin:



Pretty Narrow opening currently........WOW



not good
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By the time you know for sure, without a doubt, no question where it will make landfall...It's too late to do anything about it.
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Stay away from Battey Park..  That will be underwater!
Quoting TampaSpin:



CAT1 for NY City........at that angle won't be good.....

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Infrared loop looks to have a slight wobble to the left, maybe be minor, looks to be on track still.
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Pretty Narrow opening currently........WOW
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Should hopefully be updating in 30min to 1HR... but latest steering for Irene:



Would yield a WNW to NW (at times).
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245. hamla
a lot of crow and humble pie wil be eatin on the blog this week lol
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Quoting willdunc79:
when will we know for sure that Irene isnt going to possibly bend back to the west


In the next day or so... should see a gradual move from west of north... to the east of north.

Stay tuned.
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First few visible images show the W and S outflow healthy for the first time. 

Yes, with the strengthening comes the N turn.  Watch that A/B high though, it has legs. 
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I lurk, being vastly ignorant and preferring to learn...but am I correct in assuming that my stable temperate zone Manhattan is going to have an earthquake and a hurricane IN THE SAME WEEK?

I have old brownstone seven-foot windows. Tape them? With what?
Member Since: Posts: Comments:



Just for reference, but if this storm was a weak Storm under Hurricane status its moving into South Florida......just shows ya how the different Steering layers work.
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The eye is cloud covered again and the cloud tops continue to warm on the east side... have to see that corrected before she will reach cat 4 although pressure is already low enough to support cat 4 so winds will come up reguardless
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I mean around 3pm after work for me.
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Quoting TampaSpin:



CAT1 for NY City........at that angle won't be good.....


wow... if thats the case that's a direct hit on me with 96-110 mph winds. no way in heck people up here in CT are ready for that.
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As a reminder, I'll be posting local reports on conditions and information from the various news sources during the day today and for as long as possible tommorow and Friday. Check my blog frequently for information.
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Quoting greentortuloni:
I am loving the GDFL: miss the entire east coast until it hits NY.

Hurray GDFL!



lol you have not even seen the rest of the mode runs
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Quoting thedawnawakening3:
Irene seems to be going through a rapid deepening phase, she should continue to do so until an EWRC occurs. Could peak at 140mph 935mb. Outflow continues to become well established on the western semi circle. Need to go to work, be back around 3pm to continue to watch Irene. HH should be in the storm at that time as well correct?


HH are in the storm now.
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06z Early Cycle NHC model tracks
Irene
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Member Since: August 1, 2007 Posts: 0 Comments: 179
Irene seems to be going through a rapid deepening phase, she should continue to do so until an EWRC occurs. Could peak at 140mph 935mb. Outflow continues to become well established on the western semi circle. Need to go to work, be back around 3pm to continue to watch Irene. HH should be in the storm at that time as well correct?
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Quoting ncstorm:
The ECWMF ensembles are showing a western track..



Finally one model says that. I dont know what the other models are thinking or the NHC is thinking.
Member Since: November 1, 2003 Posts: 4 Comments: 234
Quoting islander101010:
it could go out to sea cloudburst has been saying that all along




sorry but 1st thing in the AM and am not geting started with the fish storm thing and going out too sea crap early in the Am this wakeing up so POOF you go
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CAT1 for NY City........at that angle won't be good.....
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CRS last checked in a while ago saying he had sustained at 60 mph. Hope he makes it through alright as well as our other TCI blogger.
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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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