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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628. Gorty
Quoting Gorty:
I love how everyone is so ignorant on here and totally ignored the HWRF AND GFDL CONCERNS THAT THEY WENT WEST AND THEY BOTH ARE RELIABLE.


Well said Gorty.
Member Since: November 8, 2008 Posts: 12 Comments: 1058
Quoting cat5hurricane:

Take a deep breath and relax Floodman. You're a bit too tense and assuming this morning. No one is complaining, and folks may cheer on the storm if they wish. Everyone has a different perspective and feeling about the storm.


I'm plenty relaxed...you don't know me very well if you think this is me all edgy and stuff LOL

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Quoting overwash12:
I will ride this storm out as I have every storm to hit N.C. the last 30 years. There are some very old houses on the Island I live on, built before the civil war and they did not bolt them down either!


For Ike (Cat 4 surge was expected), people who decided to ignore the certain death warnings were advised to write their SSN on their forearm using permanent marker.

If you are in the same situation, I advise you to do the same.
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6Z GFS ensembles..How far E will she go???
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The models have been useless over 6-12 hours out. The continental US was never in the direct path of Irene!
Member Since: July 4, 2008 Posts: 0 Comments: 34
Everybody infatuated with earthquake, people will be talking about it for days, and then BAM! Irene comes in for the REAL DEAL. Sidetrack your enemy then hit when not prepared.
Member Since: July 14, 2008 Posts: 1 Comments: 9628
Quoting Floodman:


You go with that...on an island...infront of a potentially strong CAT3...you get to find out first hand the meaning of your handle
Or he can change it to "deadman"
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100-110 mph winds about to move onto Acklins Island, Crooked Island, Long Cay, and Mira Por Vos Cays
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Quoting will40:


well the actual diameter of the storm isnt want counts. it is the height of the vertical stacking that counts. The better the storm is stacked vertically the more chances it can feel the weakness of a broken down ridge. The weakness is what is is looking for. Hope that explaines it a lil bit for ya.


I've read from some in here that it's the pressure of the storm that will determine how it's steered and from others the height.

Height seems to make more sense to me. Weaker storm are steered by low level winds, and stronger storms by mid and upper level winds. Please correct me if I've over simplified or and completely wrong.

Is it one or the other or a little of both?

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joe b said this when everyone had it hitting Florida and going in gulf. His forcast was over two weeks ago
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Quoting CarolinaHurricanes87:


It will show up MUCH sooner on the Miami radar, you should use that... should start showing up on their radar tonight


I took a look at the Miami radar, and i dont think the Eye of Irene will come in range..how far out does the Miami radar reach?
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Quoting HCW:
She is going annular . I hope that doesn't get me banned :)


You did not just say that...

Okay, cue the angry villagers with the torches and the hayforks!
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Quoting Thrawst:
Morning guys... Nassau is still relatively quiet. According to Baha, we had a rain band from Irene this morning, and now at my place it's relatively sunny with winds around 15 mph. Should increase late tonight as the circulation approaches from the southeast. Will update you as it nears! :)


Hopefully you'll be on the lesser side of it. Keep in contact if you can!
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Baha -- check your WU mail

How are the conditions this morning?
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Quoting marknmelb:


Ok so it's the 300-850 layer ???


Look in the lower right of the image, just to the left of the date and time. It shows the range of pressures of tropical cyclones steered by that layer. The last update I see is 966mb, which at the high end of the layer I posted (300-850).
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting overwash12:
I will ride this storm out as I have every storm to hit N.C. the last 30 years. There are some very old houses on the Island I live on, built before the civil war and they did not bolt them down either!


Are you on the coastline or an island?
You still have a couple of days to think about it.
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Quoting WeafhermanNimmy:
Either way I will be in New Bern, NC on fri aft.


Check on my house there for me. Danke!
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ground shakes, then the sky falls
Member Since: July 14, 2008 Posts: 1 Comments: 9628
Quoting SPLbeater:
I am going to be watching the Morehead city radar from now on, seems its the closest to the center track i can find


It will show up MUCH sooner on the Miami radar, you should use that... should start showing up on their radar tonight
Member Since: August 4, 2011 Posts: 0 Comments: 631
Quoting Floodman:


You go with that...on an island...infront of a potentially strong CAT3...you get to find out first hand the meaning of your handle
Will do,I know for a fact there will be people staying in Hatteras and Ocracoke.
Member Since: June 24, 2007 Posts: 0 Comments: 1466
A nice bout strengthening by Irene last night, I see.

And, no, the weakening flag was off on the NOAA ADT, contrary to apparent general perception: http://www.ssd.noaa.gov/PS/TROP/DATA/2011/adt/tex t/09L-list.txt

On now, though, but only due to a slightly cooling eye. (A warming eye is a decent indication of intensification.)
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Quoting LightningCharmer:


Don't mind the political statements in here occasionally if they are for humor or related to weather. climate or science but often they are not, especially now in an election season, however, I'm the last one who would state you don't have a right to those statements.

Is there any truth to idea that the SST's (Sea Surface Temperatures) will be reduced by Irene so the next tropical system over the same areas with have less fuel so to speak?



That might be true if Irene moves continually slowly over the bahamas and doesquite a bit of upwelling in the shallow waters, so yes thats possible that the SST's would drop a little
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602. HCW
She is going annular . I hope that doesn't get me banned :)
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Quoting CloudGatherer:


I think he's probably channeling the Dexys Midnight Runners. As long as the NHC track stays close to the northeastern megalopolis, I think we should all brace ourselves for an onslaught of "Come on, Irene" puns.


You're likely right...a friend in SF started that happy crappy yesterday
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600. Gorty
I love how everyone is so ignorant on here and totally ignored the HWRF AND GFDL CONCERNS THAT THEY WENT WEST AND THEY BOTH ARE RELIABLE.
Member Since: November 8, 2008 Posts: 12 Comments: 1058
Quoting angiest:


You are in the wrong layer.



Ok so it's the 300-850 layer ???
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Quoting trunkmonkey:
I was given a warning yesterday when I mentioned negative comments about the commander in Chief, my bad, If I want to continue to post in here, it better be positive comments only!

Suns up this morning, feet hit the ground, all is good!


Don't mind the political statements in here occasionally if they are for humor or related to weather. climate or science but often they are not, especially now in an election season, however, I'm the last one who would state you don't have a right to those statements.

Is there any truth to idea that the SST's (Sea Surface Temperatures) will be reduced by Irene so the next tropical system over the same areas with have less fuel so to speak?

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Quoting help4u:
joe b said this was a east coast storm for over a week


So did everyone else... even the best on here were saying things like "zero percent it recurves", "slim to none" chance of it missing the SE... the computer models were putting out consistent runs to tampa with alot of runs showing the fla panhandle, new orleans, and as far west as southern texas landfall.

Pretty much everyone was waaaayyy off on this one. No one ever saw an OBX (or even further east than that) path
Member Since: August 4, 2011 Posts: 0 Comments: 631
Quoting robert88:
Looks like Irene is Earl 2.0...Models have been absolutely horrible this season and where is that strong subtropical ridge that was glamourized by the almighty king EURO and GFS??? Looks like a possible repeat of 2010 on the way. Pattern change my a$$...lol



You're complaining?
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Quoting CaneHunter031472:


Sorry for the outdated post. :-( will be more careful next time.


No problem. It happens....no one is perfect.
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I am going to be watching the Morehead city radar from now on, seems its the closest to the center track i can find
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591. DVG
Quoting Minnemike:
i was gonna say.. that SW jog didn't jive with observations


It was about there 2am this morning edt.

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Quoting will40:


well the actual diameter of the storm isnt want counts. it is the height of the vertical stacking that counts. The better the storm is stacked vertically the more chances it can feel the weakness of a broken down ridge. The weakness is what is is looking for. Hope that explaines it a lil bit for ya.

Thank you!!!!
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589. NJ2S
Quoting FLdewey:


The disruption in air travel will be devastating... will make for an interesting airline contingency plan.

So who puts the plywood on the statue of liberty?


If I have a flight this weekend ,saturday to be exact is it safe?? Should I cancel and leave Monday or tuesday?
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Quoting Floodman:


Okay, now you know I love you man, and we're in the same dinghy pulling oars on opposite sides, so a word of gentle reminder: egging her on in your outside voice is considered to be in very poor taste. A nice demur golf clap is about all you can really allow yourself in public


I think he was going for a Dexy's Midnight Runners reference, though it's Come On Eileen.
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Quoting marknmelb:
Is the gap closing ???



You are in the wrong layer.

Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting oakland:
''

the date on the video is 23Aug. Please verify......


Sorry for the outdated post. :-( will be more careful next time.
Member Since: August 1, 2007 Posts: 0 Comments: 169
joe b said this was a east coast storm for over a week
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Quoting overwash12:
I will ride this storm out as I have every storm to hit N.C. the last 30 years. There are some very old houses on the Island I live on, built before the civil war and they did not bolt them down either!


You go with that...on an island...infront of a potentially strong CAT3...you get to find out first hand the meaning of your handle
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Quoting chevycanes:

that is not updated. that stops around 72W and Irene is already at 73.3W

just look at satellite and you can see its moving nw.
i was gonna say.. that SW jog didn't jive with observations
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Quoting chevycanes:

that is not updated. that stops around 72W and Irene is already at 73.3W

just look at satellite and you can see its moving nw.


73.5W and 22N Definitely moving as planned to the WNW sorry for the outdated post. :-( will be more careful next time.
Member Since: August 1, 2007 Posts: 0 Comments: 169
Quoting Floodman:


Okay, now you know I love you man, and we're in the same dinghy pulling oars on opposite sides, so a word of gentle reminder: egging her on in your outside voice is considered to be in very poor taste. A nice demur golf clap is about all you can really allow yourself in public


I think he's probably channeling the Dexys Midnight Runners. As long as the NHC track stays close to the northeastern megalopolis, I think we should all brace ourselves for an onslaught of "Come on, Irene" puns.
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Quoting atmosweather:


5 years old, east side of the town of Kendall. Got ripped by the brunt of the northern eyewall and half the house was on the other end of the street by daybreak.
Did you suffer any bit of traumatic effects when you were a kid because of this?
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Morning guys... Nassau is still relatively quiet. According to Baha, we had a rain band from Irene this morning, and now at my place it's relatively sunny with winds around 15 mph. Should increase late tonight as the circulation approaches from the southeast. Will update you as it nears! :)
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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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