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 hurricanejunky:


And the classic weather center photo:


Atleast he only asked annoying questions repeatedly..
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1176. Gorty
Quoting reedzone:
I have friends and family on Long Island who are not taking this storm seriously, brushing it off like it's another Earl. If you live on LI, this is historic, we have never seen a storm like this since Hurricane Gloria in 1991. Please, don't shove this one by and start making ur evacuation plans, Long Island is at sea level and when you have a storm that was a Category 4, the surge can be catastrophic. PLEASE, head my advice and prepare for Irene. This isn't an Earl where it recurves at the last minute, the highs are set in place and the weakness will lead it right up the coastline. A category 2 Hurricane is set for landfall as of the 11 a.m. track.


Best post so far. I agree with you.
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NOTE TO OUTER BANKS: An official notice/ruling will be made at 5:00 PM DST regarding the evacuation of Dare (the Outer Banks minus Ocracoke) County. To our tourists, if they say to go, please go...otherwise you clog the roads for the locals, when it is their turn to evacuate. For what it is worth, I am sorry for your lost vacation day or two days.
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Lets get back the tropics subject ppl,, thats what this blog is for. BTW, there was a 1 mb pressure drop as of the 11 AM advisory, so strengthening continues...
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Um, here is a way to get the blog administrator's attention... EVERYBODY and I mean EVERYBODY, hit the ! button next to Jason's posts. I have already done that myself. If you love the quality information that you get from this blog, please do us all a favor. I look to this blog for insight into models and steering and all other sorts of information (and even humor from time to time), but to have bandwidth tied up with useless information that people, like Jason post, is a severe injustice to all of us that want to learn and share thoughts.
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1171. kwgirl
Quoting air360:


Actually not really. They say never truly look past three days out. AND in EVERY discussion that we read at the very end of it they say something along the lines of:

"Users are reminded that significant errors are possible with
forecasts at longer lead times...so one should not focus on the
exact forecast positions at 96 and 120 hours."

So how can anyone justify reading the "its possibly heading towards so and so city in five days" and then totally skip the last paragraph like it's not there and then be pissed when it doesnt verify.  That's true selective reading!

Being a Keys dweller since 1960, I have been through a lot of hurricanes and a lot of near misses. I don't even know the number of hurricanes I have seen pass over the keys. Yes, we get complacent. HOWEVER, we all look at the path and listen to what the weather forcasters tell us. When I had a house to shutter, I did it as soon as I thought we would get any winds or rain. In other words, when we were in warning area. So what if it missed. Simple exercise...proved the shutters work and I didn't have to clean up the yard afterwards. I would rather be warned and find out the NWS was wrong and it went elsewhere than be taken off guard so I don't have time for shutters or any preparations. Yes, evacuating is inconvenient, and here in the Keys we have a long way to go to evaucate. But if I had a possible Cat 3 bearing down on us, I would be making plans to scoot out of here. Just because the NWS was wrong on the exact target once does not mean they will be wrong every time! Follow what your EM people tell you to do. It is for your and everyone else's safety. Just Do It!
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Quoting E46Pilot:


Well any jog west would mean increase effects on south Fl. I remeber going to bed thinking Irene was going to skirt south of PR, and waking up and it was N of PR.

With all your respect,I believe the eye of the Hurricane is following the Hurricane Center points exactly as they lay it out.I'm very confident here in Miami about the Hurricane Center confidence in their track otherwise they could easily issued Warnings this morning or yesterday,this is my own opinion after being a member of this blog for many years,the Hurricane center track in the 2-3 days range is 90% accurate.
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Irene's west jump/jog continues, Acklins Island getting pounded.
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Quoting streamtracker:


"Yeah the forecast calls for it to turn but how much faith do you have in that forecast!?"

For a two day forecast, very high level of confidence. (http://www.nhc.noaa.gov/verification/figs/OFCL_AT L_trk_error_trend_sm.gif)


Yeah but we are only talking 150 miles here. What about the fact that it was supposed to skirt south of PR, and the next morning it was north?
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1167. ph34683
Quoting notabubba:


AB1JV, first licensed 1976


My dad is and will be on OBX tomorrow through the storm (even though I told him not to!)

WB3CWK is his call sign/handle/ whatever you call it...
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1166. JNCali
Hey Levi..what are the ants doing in AK??
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I have friends and family on Long Island who are not taking this storm seriously, brushing it off like it's another Earl. If you live on LI, this is historic, we have never seen a storm like this since Hurricane Gloria in 1991. Please, don't shove this one by and start making ur evacuation plans, Long Island is at sea level and when you have a storm that was a Category 4, the surge can be catastrophic. PLEASE, head my advice and prepare for Irene. This isn't an Earl where it recurves at the last minute, the highs are set in place and the weakness will lead it right up the coastline. A category 2 Hurricane is set for landfall as of the 11 a.m. track.
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Quoting streamtracker:


"Yeah the forecast calls for it to turn but how much faith do you have in that forecast!?"

For a two day forecast, very high level of confidence. (http://www.nhc.noaa.gov/verification/figs/OFCL_AT L_trk_error_trend_sm.gif)


Yeah, they thought it was going to go over Hispanola too...not
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OK...gotta go pretend to be respectable for a few hours...Floodman...you're in charge...
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Now hj is posting the equivalent of porn...

I'll come back later. Hopefully this place will get better at being on topic rather than taking the bait.
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Quoting snotly:
Miami is now activating their new HARRP Hurricane defense shield.


And it's working like a champ lol. Florida saved because of conspiracy theories yayy!!
Member Since: August 1, 2007 Posts: 0 Comments: 182
1160. IMA
Quoting hurricanejunky:


And the classic weather center photo:


Dang it, I couldn't find that or the pic of Press-in-a-Dress! Searching has helped keep me from having as many weather tabs open, though
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Just by the latest observations from the NHC and sat tracking, it looks like the highest probability for a CONUS landfall would be a window between Wilmington NC and Pamlico Sound, NC. Again, this is just a very reasonable guess. The track could still shift some east/west
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Quoting 69Viking:
I wonder how many people in South FL on on there toes this morning knowing how close a major hurricane is to them and moving straight for them!? Yeah the forecast calls for it to turn but how much faith do you have in that forecast!? Sure glad I'm not anywhere along the East Coast for this one, it's going to be touch and go once Irene gets closer to the U.S. Coastline. She's still heading WNW from what I can tell.....How close is she going to get to Florida before she actually turns!?


"Yeah the forecast calls for it to turn but how much faith do you have in that forecast!?"

For a two day forecast, very high level of confidence. (http://www.nhc.noaa.gov/verification/figs/OFCL_AT L_trk_error_trend_sm.gif)
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jason get a jug fill it with water grab a couple tea bags throw it in there let is sit for about five minutes drink with ice. got a bad cough? or that that a chronic problem. so your watching this storm too? a good one for surfing
Member Since: September 11, 2010 Posts: 1 Comments: 4732
Is Jason serious??
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1155. scott39
Quoting Grandpato4:


Yes.
figures.
Member Since: June 13, 2009 Posts: 0 Comments: 6863
1154. Gorty
Quoting Chapelhill:
Looking at the current maps, W. Mass fall into the 5% chance of >58 mph wind and 20% chance of 37mph wind. Considering it's days away and a couple thousand miles away; I think you should relax a little IMO.


I dont really like those maps because so much can change especially some unexpected turns from west or east back to west etc...
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Quoting JasonCoolMan2004:

Dude, I gave you a chance, goodbye. you a f'n nut job. go seek some help dude. geez. kids come here. Media come here. That's just wrong oh so wrong.



Now in Sydney, Australia.
52.7°F falling
Updated at 01:00 EST
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1149. Buhdog
Quoting presslord:
ignoring him might be overrated


that would figure since his videos made him my FIRST ignore on this site (6 years in the making) I always turn my head at the wrong time!!!! Thanks for the funnies PRESS
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1148. snotly
Miami is now activating their new HARRP Hurricane defense shield.
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1147. scott39
Did I miss nakedness after I ignored Jason?!?!?
Member Since: June 13, 2009 Posts: 0 Comments: 6863
I can't stop laughing this AM....did the teacher not only leave the class, did he leave the school??? Cat 4 out there and this mess going on?
sheesh
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Quoting portcharlotte:
In the last hour or so irene has made a sharp left turn..I know it's the wobble but wobbles can add up


The wobbling continues....
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NEW BLOG POSTED, and category 4 back in the forecast for Irene. This really makes me think of Hurricane Earl does it not? looks like Earl too,just slighty smaller..
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1142. truthy
For those of you trying to "ignore" a certain user, there is an alternate way. You can go to "Mail" at the top of your screen, click on the "lists" tab and then enter his name in the "block user" field. It worked for me when my "ignore" button wouldn't.
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Quoting Floodman:


Ahhhh...IE9; I have resisted the upgrade lo, these many months and it has paid off handsomely, vis, my ability to banish the aforementioned indiviudal...



Google chrome wiped him out when I hit ignore.
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Quoting Gorty:
I can't believe I am saying this but my house has a 50/50 shot at destruction... 50 chance it will get wrecked and 50 chance she will go east of me sparing me.
Looking at the current maps, W. Mass fall into the 5% chance of >58 mph wind and 20% chance of 37mph wind. Considering it's days away and a couple thousand miles away; I think you should relax a little IMO.
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Quoting presslord:


in that case...How are you able to respond to me?!?!
Well, I have the option to expand and reply to any of the minimized posts.

But, yours aren't among those not visible (a very few are).
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1137. TX2FL
Does anyone have any idea when they may issue evacuation suggestions/plans for the Jersey Shore? I have some friends that are planning to go for the weekend, but I think if it's going to hit that area on Sunday, they'd be evacuating Friday or Saturday..
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Quoting presslord:


which fact makes their forecast look pretty good


Yes I think their initial forecast was pretty good all things considering. I'm going to calculate how close Irene actually gets to Miami when she passes by, I'm betting it's going to be 250 miles or less. It's nice that you can now add the weather to Google Earth. When Irene's eye is parallel with Miami all I have to do is use the ruler to measure the distance between the two, neat stuff! As it stands now Irene is approx. 495 miles SE of Miami.
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It's funny as soon as a proclamation is made that irene is turning NW she heads west....no so fast NHC
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Quoting Floodman:


Ahhhh...IE9; I have resisted the upgrade lo, these many months and it has paid off handsomely, vis, my ability to banish the aforementioned indiviudal...



People still use IE, thats the problem. Use Mozilla Firefox, it is much better, and no problems.
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Quoting Floodman:


WHERE? WHERE?

down son, lol
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Quoting IMA:


Wow, I thought Press had retired from that particular profession


these chicks are even hotter than me
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hmmmm....
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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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