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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Wind field of Irene as of 8 am EDT...
As of right now, TS-force wind extend about 100 miles to the west of the eye. Hurricane force, about 45 miles. Maximum winds, 102 knots, 21 miles straight north of the eye.

Member Since: Posts: Comments:
Quoting air360:
I will be the first to say i do not know exactly what im looking at...so im really just using my basic understanding with this (which is why im asking for someone to explain)

Essentially what im tying to understand is that it looks like the gap is starting to get blocked off a bit from the bermuda high/ridge to the east if you look at the 0z compared to the 12z. �In the 0z the gap was huge..now it looks like its pushing all the way onto the NC coast. �am i right in seeing this? �Would this hold it closer to the coast than forecast?

12z



0z


You are thinking the same that i was aminute ago, I would call that a possibility, combined with the average error at 4 days out from the NHC that is possible it ispushed back onshore:/
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Current Projected Track of Irene from Met Steven DiMartino.

http://www.nynjpaweather.com/2011/08/24/the-offic ial-ny-nj-pa-weather-forecast-for-hurricane-irene/

He is leaning a bit west of the official NHC track as of 8AM, and thinks the GFS has now over forecasted the strength of the tough on Sat/Sun. He is leaning on the way the Euro has handled the pattern over the northern US (which is the most important factor (but not the only one) to determining the exact track. He feels that so far the Euro is doing a better job at predicting the strength and speed of influences over the northern US.

But does caution (as a responsible met would) that the factors in the pattern don’t have to change much to move this 150- or more miles offshore, causing substantially less impact for a lot of people. He doesn’t think there is much to support a WESTWARD shift in track at this point if any.

I can say this Steve is a master when it comes to understanding the upper level patterns over the northern US and how models behaving in regards to forecasting them. He has nailed several of the historic Nor’easters over the last 2 winters (such as the boxing day blizzard when models never caught on until the last minute)
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674. hamla
Quoting butterflymcb:That sounds so familiar. Most of the people that said this on the coast of MS before Katrina sounded just like this, "This house survived Camille! Nothing can happen to this house!"...>Well, many of those people are not around to tell us about it.
it was just like the hurricane party during camile who were told to leave by the sheriff and refused not around any more just give name of next of kin
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673. Gorty
Henry thinks the really far east models are too east. Even I think the models will go back west toward the GFDL and HWRF
Member Since: November 8, 2008 Posts: 12 Comments: 1058
Quoting ncstorm:
can someone answer this..if the NHC forecasts has the storm passing 70 miles to our east (wilmington), are they speaking of the center (eye) passing to our east?


Yes.
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The trough that is to finish curving Irene to the North and North east is forcasted to be slightly weaker than was modeled yesterday.

Todays Forcast -
Link

Yesterday's Forcast
Link
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Quoting cat5hurricane:

Fair enough. I got the wrong impression then.


LOL...I get that alot...where you at cat5?


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Quoting rkay1:
This is great that its looking like there will be no direct hit.  On the other hand, these forecasts definitely pranked the entire East coast.




Exactly. This huge shift from the central gulf to eastern gulf to south florida to SC to NC to the NE...... is going to make millions of people in these areas more likely to ignore future warnings and delay preparations. I know a forecast is what it is, but when they have been dead wrong every day this week, its like the boy who cried wolf... I fear people will take the threat less seriously when they seem clueless on the forecasting
Member Since: August 4, 2011 Posts: 0 Comments: 631
Quoting air360:

I will be the first to say i do not know exactly what im looking at...so im really just using my basic understanding with this (which is why im asking for someone to explain)

Essentially what im tying to understand is that it looks like the gap is starting to get blocked off a bit from the bermuda high/ridge to the east if you look at the 0z compared to the 1200.  In the 0z the gap was huge..now it looks like its pushing all the way onto the NC coast.  am i right in seeing this?  Would this hold it closer to the coast than forecast?

12z



0z


There's a shortwave moving in which may reopen the gap between the ridges. Remember, you are looking at a snapshot that's good for about three hours.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
I have been reading for a long time, but just signed up for the blog. Great information and Maps. I really appreciate that. We (my family) went through the 2004 hurricane season in Florida with an infant so that being said I am not a complete storm newbie. I live very much inland between Greenville, SC and Charlotte, NC now.

My question is this, seeing how Charley pulled a Right hand turn in 2004 what would prevent Irene from making a wobble or jog etc to the left as she gets closer to land? Would it be the bank of clouds that are currently over the mountains at the TN/NC border.
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can someone answer this..if the NHC forecasts has the storm passing 70 miles to our east (wilmington), are they speaking of the center (eye) passing to our east?
Member Since: August 19, 2006 Posts: 13 Comments: 16222
Quoting CBJeff:
NYC may be nothing like New Orleans, but both the Big Apple and the Big Easy have a lot of infrastructure at or below sea level. A significant storm surge (or even just a lot of rain) could quickly flood underground utility and transportation assets.

And drive an absolute army of rats to the surface…
New York subway's rats are the largest I have ever seen... my take on this Hurricane is that it will go far east enough, not to cause significant damage to the City,HOPEFULLY. I remember Doria when it swepts towards the city, back in the early seventies,(1971?not sure) but made a turned in the last minute.
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661. Gorty
Quoting HiWay:


The new GFDL and HWRF models, if accurate, would be absolutely devastating.


They are reliable and MUST be included as a possible track.
Member Since: November 8, 2008 Posts: 12 Comments: 1058
660. HiWay
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


The new GFDL and HWRF models, if accurate, would be absolutely devastating.
Member Since: August 17, 2007 Posts: 0 Comments: 55
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.


The Dexy's song title was 'Come on Eileen'.

Has there ever been a hurricane Eileen?
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Quoting Floodman:


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

Hey Flood...I was feelin edgy until they finally shifted that track away from us..Talk about feeling relieved....Hope you are doing well.
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Quoting Stats56:


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.


Whoa. Don't hold back, tell us what you really think.
Member Since: August 18, 2010 Posts: 14 Comments: 1605


time for da am FunkTop,



Member Since: July 3, 2005 Posts: 428 Comments: 129796
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.
Both of those have been leaning west the whole time.. I suppose you weren't paying attention when only those two were still taking it into the gulf while the others had moved on up to the carolinas

Member Since: Posts: Comments:
I will be the first to say i do not know exactly what im looking at...so im really just using my basic understanding with this (which is why im asking for someone to explain)

Essentially what im tying to understand is that it looks like the gap is starting to get blocked off a bit from the bermuda high/ridge to the east if you look at the 0z compared to the 12z. In the 0z the gap was huge..now it looks like its pushing all the way onto the NC coast. am i right in seeing this? Would this hold it closer to the coast than forecast?

12z



0z
Member Since: October 13, 2002 Posts: 0 Comments: 275
Quoting Gorty:


Well said Gorty.


It's too bad that stupidity isn't painful
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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.


Better safe than sorry. A wobble west and your house is in line for the worst of it.
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Quoting Gorty:
TWO RELIABLE MODELS THE HWARF AND GFDL WENT WEST... THIS PUTS ME ON THE STRONGEST SIDE OF THE STORM.

THIS IS WHY THERE IS SO MUCH UNCERTAINTY.

I live in western Mass.
What? Cannot hear you.

HWRF and GFDL were among the last to come over to the east, so the reliability, at this moment, is, umm, somewhat debatable.

I do think that GFDL is performing much, much better with Irene than it was, but how certain can one be with any of it's solutions for Irene for the duration? Now, if you see ECMWF and GFS jump over to a track to your west, I'd believe it.

About the Navy models: They were a day ahead of the others in giving a track along the Outer Banks. We commonly discount NOGAPS as terrible at TC track forecasting, but with Irene, it made all of the others look bad, IMO. Not sold that they have been significantly improved, long-term, yet.
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648. ackee
90L looking good this morning
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Quoting CoopsWife:


ROFLMAO - Amen to that! :)


LOL
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There seems to be a High Pressure area over the waters off of the VA/NJ coastline, and it is forecast to head NE and strengthen to 1025 mb. This might be what could push Irene back into New England after north of the OBX.....
Link
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pressure dropping like a rock
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642. JeffM
Definitely looks like Earl 2.0.
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Quoting rkay1:
These are pretty impressive models they are using.  Starting out pointing at GoM from Houston to NOLA, North FL, South FL, GA, SC, NC and now NYC.  Its running out of land to point at :(


Why the sad face at the end???????
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Quoting Floodman:


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



ROFLMAO - Amen to that! :)
Member Since: Posts: Comments:
Quoting ackee:
agree think this seasons see few land forming system rest of the seasons I thiink we have many fish storm


It does seem like fishing seasons starting up... hopefully the NE is included and spared from Irene.
Member Since: August 4, 2011 Posts: 0 Comments: 631
Quoting LightningCharmer:


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?



A vertically stacked, well organized storm will, in general, have a lower pressure. The taller the storm, regardless of pressure, the more the weakness will be felt
Member Since: Posts: Comments:
Quoting PELSPROG:


Are you on the coastline or an island?
You still have a couple of days to think about it.
Knotts Island. Its protected by the Outer banks,but the ocean has been known to create new inlets as we have seen with Isabel. On a Northeast wind the sound water gets pushed south,south winds would bring water up.
Member Since: June 24, 2007 Posts: 0 Comments: 1497
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!


That sounds so familiar. Most of the people that said this on the coast of MS before Katrina sounded just like this, "This house survived Camille! Nothing can happen to this house!"...

Well, many of those people are not around to tell us about it.

Those big, beautiful houses that had survived Camille with not much damage were not only destroyed...they were gone. All we found of my friends house was a piece of her silver set.
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Currently Irene is following a path between HWRF and the average track of NHC (ie slightly west of NHC) and pretty much on schedule.
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Quoting SPLbeater:


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


Thank you for the answer. So some good is coming from Irene in a way even though I read on here yesterday, she's taken at least one life in flooding in Puerto Rico.

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631. ackee
Quoting rkay1:
Right on point.  Even the new waves are curving out.  We're likely to see this pattern stay.  Earlier GOM systems went straight to lower Texas and Mexico.  Sounds a bit familiar?

agree think this seasons see few land forming system rest of the seasons I thiink we have many fish storm
Member Since: Posts: Comments:
Lets face it even as a cat 3 hurricane force winds only extend out 40 miles. The computer models are in near perfect agreement of Irene being located very close to the OBX. This would mean that just about everyone south and west of the outer banks will receive little to nothing... weak tropical storm force winds, some rain... worst thing will be huge waves and im guessing a lot of beach erosion.

OBX... take it seriously. Shes a monster, and coming either right for you or very close.

Further north of OBX... Looking ominous but Id keep a very close eye on her.

I really think everyone S and W of OBX can breathe a sigh of releif, as I see no way she affects many of us given the perfect agreement by the models.
Member Since: August 4, 2011 Posts: 0 Comments: 631
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

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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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