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 ncstorm:
Please stop bashing the NHC..who would you rather have forecasting and predicting the path of the storm, the blog?? If that happened, Irene would have made a double loop over Florida, traveled to the Gulf and sat there and became a cat 6 in the "hot bath waters" and then hit NO and traveled back to Florida and rode up the entire east coast destroying NYC while poor Texas still didnt get any rain..I believe the NHC are doing a great job..
This blog does attract a lot of "storm junkies" as one would expect.

This is a common and well-known component of a particular type of personality, which is in itself commonplace. And to be honest, many meteorologists are actually storm junkies, or started out that way. It may be what compelled them to study meteorology, acquire their degree and begin working in the field.

Once they get their degree though, they must learn to temper their enthusiasm about great storms and their impact on the lives of large numbers of human beings, most of whom are not storm junkies and normally not interested at all in the weather.

When a storm junkie can anonymously take part in a blog like this, their zeal for not only the storms themselves but for the potential of drastic impacts from these storms becomes ever the more apparent. It is like a high to them and like any junkie, they want more and more of it, not less. So when a storm fails to unfold in a way that may cause grave impacts as the junkie hoped it would, their disappointment can turn to a more or less evident frustration on a blog like this. And that in turn can turn even to bitterness, such as at the NHC. The NHC is probably about as close as one could possibly get to a completely unbiased an objective institution in all of science. They don't wish a storm on anyone, just report on the progress and evolution of systems, to the very best of their ability.

As the quoted post above indicates, had this blog determined the fate of Irene, it would indeed have crisscrossed Florida like a Cat 5 buzz saw and likely would have made a second and devastating landfall somewhere else as well.

There is nothing at all wrong with being interested in meteorology. Likewise, there is nothing wrong with being interested in great and powerful, potentially lethal tropical cyclones. But before one either secretly or even not-so-discreetly "wishes" for a great storm to devastate any given area, one should consider what it might feel like to feel the intense pain that comes from tragedy, since tragedy always accompanies the landfall of a major hurricane and very often en masse.
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I think Jeremy Wheeler of WAVY 10 in Hampton Roads has a pretty good blog about what he thinks will happen. Link
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Quoting Floodman:


There's one in every bunch; typically it's me so I do appreciate you taking over for a while...whew! I needed a rest


I'm leaving so your back on duty.
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you should all ignore Floodman...that guy's nothin' but trouble...
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Complete Update

Off to work... you guys play nice... stay safe Baha...looks like it might also miss the banks..

TS BUSTED FORECAST ALIBI





Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting oracle28:
The good thing about a strengthening storm is the increased recurve potential.


Interesting, how so? Could you 'splain it for me?
Remember, there are no dumb questions, just dumb questioners and I are one!
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Quoting CarolinaHurricanes87:

Off to work, glad my area will be spared but even more glad I didnt waste $$$ buying supplies like I was considering doing


After all the bashing New Orleanians got for not getting out, not being prepared, blah blah blah, it just really yanks my chain to see people like you on here talking about wasting money on supplies, etc etc etc.
YOU LIVE IN A HURRICANE-PRONE AREA. Just like I do. And it is YOUR responsibility to be prepared and self sufficient year after year after year. You should not be whining about wasting money, or glad that you didn't (it's peak season!!!), you should have this budgeted out EVERY year, and you should already have the majority of your supplies stocked by June 1.
I don't mean to come across like a shrew here, but seriously. This is the personal responsibility everyone along the Gulf Coast and Eastern seaboard should be taking seriously every single year. To do otherwise would be like living in Detroit without a snow shovel and sweating every single cold front. Oh! Thank God I didn't waste money on a snow shovel! That blizzard totally missed us and hit Flynt instead! Stupid meteorologists!
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Quoting Jax82:


A 7 day cone would just engulf from Brownsville to Maine, lol


Sounds like a Reedzone prediction.
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I think Jeremy Wheeler of WAVY 10 in Hampton Roads has a pretty good blog about what he thinks will happen. http://blogs.wavy.com/2011/08/24/hurricane-irene-i n-the-bahamas/
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Quoting E46Pilot:
NHC should do away with the center-line forecast on the five day and just show the cone. People get hung up on the center-line, and completely ignore the cone. Center-line is fine for the 3 day, but it should end there, and then just show the cone for the five day.


I was going to post the same.
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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


for brother Overwash... Crystal Beach after Ike.



The storm surge arrived earlier than predicted by the trusted local forecaster Dr. Neil Frank and trapped many, dooming them to a rather unpleasant death. I recall that some credited Dr. Masters, and folks from this blog for giving evacuation advice that ultimately saved their lives. Does this apply to Grandpa? I dunno, but erring on the side of caution and safety would seem to me the smart course of action when failure to take timely action could mean death.
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Quoting Jax82:


A 7 day cone would just engulf from Brownsville to Maine, lol



yea....I can do a 7 day cone with a crayon stub and a pink sheet of construction paper
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I am thinking this thing is going off the coast (like most storms) and the obx will be spared once again...unless there is a movement at all to the west, then we will be in trouble.
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Quoting PrivateIdaho:
I copied my genetic code on my arm so I can be identified.



There's one in every bunch; typically it's me so I do appreciate you taking over for a while...whew! I needed a rest
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Irene is a beautiful hurricane.
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Irene seems to be trying to make that turn to the NW to me. The longitude line to watch is around 77W. If Irene gets past there before turning N, S/N Carolina looks like a bulls eye to me.
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Quoting MrstormX:


We all know the quality of this site is going down, ppl need to stop the elementary school antics. There is a major hurricane forecast to strike the United States, and here we have ppl flagging innocent posts and having side conversations about idiot bloggers like JFV. This is my last post non-weather related...I hope this becomes a pay only blog, cause this is getting stupid.


Amen! +10000
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Quoting E46Pilot:
NHC should do away with the center-line forecast on the five day and just show the cone. People get hung up on the center-line, and completely ignore the cone. Center-line is fine for the 3 day, but it should end there, and then just show the cone for the five day.


that's a reasonable solution
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Quoting MrstormX:<
/strong>


We all know the quality of this site is going down, ppl need to stop the elementary school antics. There is a major hurricane forecast to strike the United States, and here we have ppl flagging innocent posts and having side conversations about idiot bloggers like JFV. This is my last post non-weather related...I hope this becomes a pay only blog, cause this is getting stupid.


I totally agree
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The good thing about a strengthening storm is the increased recurve potential.
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897. Jax82
Quoting nrtiwlnvragn:


Using that logic however in 2000 the 3 day cone was just as inaccurate as the current 5 day cone. So we should have had then a 24 or 48 hour cone. In my opinion the 5 day should stay, as they are working on a 7 day cone currently, doing in house this year a 7 day forecast, which I don't think is necessary. NHC claims that the professionals in Emergency Management are asking for the 7 day.




A 7 day cone would just engulf from Brownsville to Maine, lol
Member Since: September 2, 2008 Posts: 1 Comments: 1261
Quoting nrtiwlnvragn:


Using that logic however in 2000 the 3 day cone was just as inaccurate as the current 5 day cone. So we should have had then a 24 or 48 hour cone. In my opinion the 5 day should stay, as they are working on a 7 day cone currently, doing in house this year a 7 day forecast, which I don't think is necessary. NHC claims that the professionals in Emergency Management are asking for the 7 day.



I understand your reasoning but the reason for the 5 day forecast is for us Navy folk who need that amount of time to sortie ships.
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Quoting nrtiwlnvragn:


Using that logic however in 2000 the 3 day cone was just as inaccurate as the current 5 day cone. So we should have had then a 24 or 48 hour cone. In my opinion the 5 day should stay, as they are working on a 7 day cone currently, doing in house this year a 7 day forecast, which I don't think is necessary. NHC claims that the professionals in Emergency Management are asking for the 7 day.




One could argue that models have probably come along way in a decade too, so that has to be a factor in older 3-day models.


A 5-day model with no center line should be fine in my view as well.
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Quoting 69Viking:
A couple of quotes from the NHC people seem to be missing. When you read the forecast discussions read the whole thing so you get all the information. These messages are typically found at the bottom of the forecast discussions the NHC publishes, read and heed!


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.

DO NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT DAYS 4 TO 5...SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE FORECAST
TIMES ARE 200 AND 250 MILES...RESPECTIVELY.

+1000000000. People here just look at the track line and not everything else, Irene is a large storm.
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Quoting Grandpato4:
I do not understand why my posts are being flagged when they are stating fact. I am just about done with this website. I see much worse stated on here day after day that gets praise and I state an island is accessible only by ferry and the post is removed.


Maybe if you stayedon the tropics subject(like it says to do above where you make a comment) you wouldnt have that problem.No offense. Now,when are the HH goin back into Irene?
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Quoting nrtiwlnvragn:


Using that logic however in 2000 the 3 day cone was just as inaccurate as the current 5 day cone. So we should have had then a 24 or 48 hour cone. In my opinion the 5 day should stay, as they are working on a 7 day cone currently, doing in house this year a 7 day forecast, which I don't think is necessary. NHC claims that the professionals in Emergency Management are asking for the 7 day.





but one could reasonably assume our forecasting skills have improved since 2000....and as for the EMC folks...I'm not real sure what good a 7 day forecast is if it isn't accurate
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Quoting Grandpato4:
I do not understand why my posts are being flagged when they are stating fact. I am just about done with this website. I see much worse stated on here day after day that gets praise and I state an island is accessible only by ferry and the post is removed.


Just so you know, your post was likely lost; posts can be removed but you typically see something telling you that the content was inappropriate and a placeholder where it was removed. The next level of admin action is to ban you.
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Quoting 69Viking:
A couple of quotes from the NHC people seem to be missing. When you read the forecast discussions read the whole thing so you get all the information. These messages are typically found at the bottom of the forecast discussions the NHC publishes, read and heed!


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.

DO NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT DAYS 4 TO 5...SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE FORECAST
TIMES ARE 200 AND 250 MILES...RESPECTIVELY.


Seems to me they were off by significantly more than 200-250 miles. How far away are Miami and NYC lol
Member Since: August 4, 2011 Posts: 0 Comments: 631
Quoting Floodman:


Invest 90L off Africa and slightly south of the Cape Verde. In additon, there was one HELL of a storm happening in central Africa yesterday

True. And what may eventually become 91L is about to step onto the dance floor later today:

Click for larger image:

Appropriate tropical weather-related image.
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Looks like the Acklins Island in in for a direct hit.
Population is only about 400 people.
Member Since: September 3, 2008 Posts: 0 Comments: 65
885. MahFL
Outer bands on the radar now....


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Quoting CaneHunter031472:
12z Early Cycle NHC model tracks
Irene

Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)


Dynamic Models (More sophisticated models)


Those are from yesterday and old
Member Since: July 27, 2011 Posts: 0 Comments: 204
Quoting KirbyPuckett34:
786. ncstorm 2:06 PM GMT on August 24, 2011

Please stop bashing the NHC..who would you rather have forecasting and predicting the path of the storm, the blog?? If that happened, Irene would have made a double loop over Florida, traveled to the Gulf and sat there and became a cat 6 in the "hot bath waters" and then hit NO and traveled back to Florida and rode up the entire east coast destroying NYC while poor Texas still didnt get any rain..I believe the NHC are doing a great job..

I couldn't have said it better myself. Don't understand why people hope for disasters


you are totally wrong, that this imprecisely nhc forescat and Irene in the east with less danger to the U.S., does not mean we want a catastrophe here, what would happen if the cone had been the East and the storm had gone to the coast in less than five days? Here we talk about not having accuracy With The models
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125mph imo at 11:00
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NHC should do away with the center-line forecast on the five day and just show the cone. People get hung up on the center-line, and completely ignore the cone. Center-line is fine for the 3 day, but it should end there, and then just show the cone for the five day.
Member Since: Posts: Comments:
A couple of quotes from the NHC people seem to be missing. When you read the forecast discussions read the whole thing so you get all the information. These messages are typically found at the bottom of the forecast discussions the NHC publishes, read and heed!


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.

DO NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT DAYS 4 TO 5...SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE FORECAST
TIMES ARE 200 AND 250 MILES...RESPECTIVELY.
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Uh oh...time to break out your *poof* list again, everyone...*sigh*
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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.