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 superpete:
Morning Kman. I saw the early models showing it moving NW early in the run.Hope Irene has not inflicted too much on T & C overnight.


We will get updates from there soon I am sure.
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Quoting Grandpato4:
The local news is saying that Irene may move further east than projected. This is all very good news and I almost feel silly having them put the hurricane shutters on the house today. I'm feeling much better here.
Good morning all. Granpato4, I thought you were going to leave. I am not sure exactly where you are, but since this big storm is heading your way, it is better to be safe than sorry. If you have nothing better to do, like work, etc., you should consider evacuating early before the roads get jammed with hoards of people fleeing the coast. A nice impromptu visit to your family further inland. I just keep picturing that dune you talked about so I know you are in a vulnerable spot. Even if you don't get the eye, the storm is going to push the ocean into shore.
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RENE NOW A CATEGORY 3 STORM, EXPECTED TO STRENGTHEN MORE

Hurricane Irene has developed into a Category 3 storm with winds near 115 mph, and the storm is expected to strengthen further throughout the day.

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Hurricane Irene
The 8 a.m. update from the National Hurricane Center reports that hurricane-force winds extend out 40 miles from the storm's center, with tropical storm-force winds up to 205 miles.

Irene is now over the southeastern Bahamas, bringing storm surge of 7 to 11 feet, and rain from 6 to 12 inches.

Forecast models continue to keep Irene east of Wilmington, instead making landfall closer to Morehead City or on the Outer Banks.

Southeastern North Carolina is still in the cone of uncertainty, and Wilmington is still likely to be affected by strong winds and rain.

but NOT cat 3 or 4 winds thank God
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Quoting BobinTampa:


still trending east though. if that continues over the next day or too, than it is buh-bye.

Exactly, that is the intent of the graphic, to show the trend.. buh-bye
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524. hamla
as big as irene is and if it grows bigger it would be bigger than the GOM WOW
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Come on Irene!!!!!
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522. HiWay
Quoting FLdewey:


Hahahaha... I won't ask how they protect the Washington Monument.


Well, I hear they have this big rubber sheath they roll down over it to prevent any debris from damaging the surface...
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bobintampa,

good morning. just curious, is this the system which the NHC has listed at a 40% of developing?

do you have the link?
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Quoting DookiePBC:


Would there be something ironic to New Yorkers fleeing to South Florida to avoid a hurricane!? LOL...it would be Snowbirds in August!
If this post was on facebook i'd like the "i Like it" icon!
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Quoting BobinTampa:


A perfect example of why you should never take evacuation advice from this blog.



Perhaps. But he was talking about having a wife that was extremely ill. He is not out of the woods yet, and should still be considering evacuation. There are already warnings and evacuations happening on OBX.
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Quoting Rainman32:
.. Just updated that graphic, you can say a longer buh-bye now.





still trending east though. if that continues over the next day or too, than it is buh-bye.

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Quoting CHinFL:
Question from an older rookie- I have heard and read how a hurricane can get large enough to "effect its own weather- ie. moisten the envirement, push out shear , etc" but can a hurricane that grows strong and large actually impact its on stearing- can it influence the highs and troughs that usually stear it? I'm facinated by weather and trying to learn!


It can, pump the ridge...

Often talked about by Westcasters, but rarely if ever seen.
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Quoting FLdewey:


Buh bye...
.. Just updated that graphic, you can say a longer buh-bye now.



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Question from an older rookie- I have heard and read how a hurricane can get large enough to "effect its own weather- ie. moisten the envirement, push out shear , etc" but can a hurricane that grows strong and large actually impact its on stearing- can it influence the highs and troughs that usually stear it? I'm facinated by weather and trying to learn!
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Quoting Grandpato4:


I am so glad I didn't leave earlier in the week. I had people on here telling me I should have left on Monday. It pays to wait it out it seems.


You still very much need to keep an eye on it.
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Pinhole "Stadium Effect"

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Just want to say for those concerned about when Irene is going to make the turn...

SUMMARY OF 800 AM EDT...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...21.9N 73.3W
ABOUT 55 MI...85 KM SE OF ACKLINS ISLAND BAHAMAS
ABOUT 335 MI...540 KM SE OF NASSAU
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...957 MB...28.26 INCHES

This storm hasn't been doing much on the 300 heading so far. That slowdown overnight was because Irene was turning.

Let's see how many more 295 headings we see out of this baby...

BTW, the track takes the eye right over the settlement of Delectable Bay, Acklins. Sure hope it's still delectable after Irene is gone...

I gotta run. I'll be back in a few hours, and should have a few pictures of what's happening in Nassau today.

Again, if you are in the Bahamas or TCI and have information or queries, please feel free to post them in my blog. Just lick on my handle in any of messages to get there.

Ya'll have a GREAT day!
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ANYBODY THINK THE EYE'S GONNA GET BIGGER?!
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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?


plywood? cmon man. everyone knows that they have giant goggles and snorkel that they put on her.


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Complete Update

TS BUSTED FORECAST ALIBI





Member Since: October 1, 2007 Posts: 81 Comments: 26511
505. HiWay
It definitely looks to have started a northern wobble on the last couple of frames. If we're lucky and that continues we may only have to deal with tropical storm force winds brushing the coast and the eye staying off shore. The next few hours are critical in these steering currents to whether or not we're gonna have a landfall or not. I think this RI will change the next model runs significantly, hopefully for the east.
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Quoting BobinTampa:
if this approaches NYC as a major, it will be the most covered event in history. Every network will go 24/7 on the coverage.

It will become nauseating to jealous florida wishcasters.


Would there be something ironic to New Yorkers fleeing to South Florida to avoid a hurricane!? LOL...it would be Snowbirds in August!
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Quoting BahaHurican:
Morning kman... I haven't heard from CRS yet this morning. He was on around 2 a.m. with power out, to crank his generator and check the 2 a.m. update. So far reports out of TCI have been that damage has been relatively minimal. However, I've only heard from Grand Turk residents, and Provo was much closer to the centre.

Hopefully he'll be in once he gets up and cranks his generator again.....


Thanks for that. Provo would almost certainly taken it a lot harder. I know that your Islands are going to take a bad hit as well but fortunately many will now be on the West side of the system which is a blessing. maybe the track will pull east a bit more today, it certainly looks like the system is pulling up to the N a bit. As strong as Irene is now poleward is where it wants to go.
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Quoting kmanislander:


90L does not look like it is coming too far West, hence no one is interested in it at this time. In fact the blog has slowed way down once the track to Fla and the GOM moved East.
Morning Kman. I saw the early models showing it moving NW early in the run.Hope Irene has not inflicted too much on T & C overnight.
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Joe Bastardi is probably going crazy,see I told you guys....LOL
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Quoting Orcasystems:


they will make it sound like Katrina was a summer rain storm... going to be fun


and all of us florida bloggers will want to talk about the latest GFS run that has a storm threatening florida at 240hrs.

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Quoting wxobsvps:


certainly is. latitude is important and sooner is better. a little confused by the 594dm ht out of Bermuda, however.



Does this mean the high is staying stronger trying to keep Irene from making that N turn too fast?
Member Since: August 4, 2011 Posts: 0 Comments: 631
Large cloud field with Irene.

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Quoting Grandpato4:


I am so glad I didn't leave earlier in the week. I had people on here telling me I should have left on Monday. It pays to wait it out it seems.


A perfect example of why you should never take evacuation advice from this blog.

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Quoting Grandpato4:


I am so glad I didn't leave earlier in the week. I had people on here telling me I should have left on Monday. It pays to wait it out it seems.


Take any suggestion on this board with a grain of salt.

I would only evacuate if told so by the local authorities, certainly wouldn't listen to a 15 year old on a message board...
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8:00am Advisory
*Click on graphic for enlarged view
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Quoting BobinTampa:
if this approaches NYC as a major, it will be the most covered event in history. Every network will go 24/7 on the coverage.

It will become nauseating to jealous florida wishcasters.


they will make it sound like Katrina was a summer rain storm... going to be fun
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting superpete:
Stormwatcher-I asked this before & got lambasted by someone as a troll. Best to stick to Irene discussion...


90L does not look like it is coming too far West, hence no one is interested in it at this time. In fact the blog has slowed way down once the track of Irene to Fla and the GOM moved East.
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9 minutes ago (this will stay at the 8:40 image):

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Quoting BahaHurican:
I hope you got all ur stuff done, too! LOL

Don't forget to post any updates info etc you get in my blog.


Will do. I have sat communications with Exuma, Eleuthera, Harbour Island, Abaco and Grand Bahama. We will see how long they are able to keep in touch.
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Just a quick question. Long time lurker, and I have learned soooo much. Thanks Dr. M and Levi and everyone else.
Over the years, there has been some reference to the fact that if the storm is too small or really large, the storm might not feel the pull and turn north. Really large storms sort of make their own environment and go their own direction.
Could this happen with this storm? She is a big un!
I live in S FL and will not rest easy until she is at least past 30N Lat (am at around 27N).
Thanks in advance for any answers.
And good morning to all.
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Quoting kmanislander:
Good morning

Irene really got it together overnight as we were discussuing last night. CAT 3 no surprise with the pressure falls we were seeing.

Any word from TCI bloggers like CRS ??
Morning kman... I haven't heard from CRS yet this morning. He was on around 2 a.m. with power out, to crank his generator and check the 2 a.m. update. So far reports out of TCI have been that damage has been relatively minimal. However, I've only heard from Grand Turk residents, and Provo was much closer to the centre.

Hopefully he'll be in once he gets up and cranks his generator again.....
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484. Jax82
She's gonna get stronger.



Member Since: September 2, 2008 Posts: 1 Comments: 1261
I am feeling better with the increase of latitude now. After Frances, Jeanne, and Wilma just a bit wary is all. They usually have a few tricks it seems :).
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09L/MH/I/C3
RI FLAG (ON)
MARK
22.98n/73.13w





ALWAYS FOLLOW NHC/TPC FORECASTS FOR ALL WARNINGS REGARDING THIS STORM
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Quoting Grandpato4:
The local news is saying that Irene may move further east than projected. This is all very good news and I almost feel silly having them put the hurricane shutters on the house today. I'm feeling much better here.


that's part of living close to the ocean during hurricane season. You'll put up your shutters 10 times for every one time you'll actually need to.

If you don't put em up, that's when you'll get hit.
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Expecting the NW turn sooner. Forecast cone on track for the most part.
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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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