Category 2 Irene Approaches The Bahamas

By: Dr. Jeff Masters , 7:51 AM GMT on August 23, 2011

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As of 2am EDT, Hurricane Irene was located at 20.1N, 69.7W, 135 miles southeast of Grand Turk Island. It was moving west-northwest at 12 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 978 mb. Hurricane warnings have been issued for the northern coast of the Dominican Republic from the Haiti board to Cabo Engano, the southeastern and central Bahamas, and the Turks and Caicos islands. Hurricane watches have been posted for the north coast of Haiti from Le Mole, St. Nicholas to the Dominican border and the northwestern Bahamas. Tropical storm warnings are in effect for all of Haiti and the southern coast of the Dominican Republic from Cabo Engano to Santo Domingo.

5AM Update
As of 5am EDT, Hurricane Irene was located at 20.3N, 70.1W, 105 miles southeast of Grand Turk Island. It was moving west-northwest at 12 mph with maximum sustained winds of 100 mph, keeping it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 978 mb.

Figure 1 shows that Irene is maturing into a vigorous storm, with apparent waves in the western edge of the cirrus outflow.


Figure 1 IR satellite view of Irene taken at 135AM EDT, August 22, 2011

Track Forecast

Irene is forecast to move to the north-northwest, passing over all of the Bahama islands by Thursday evening, at which points it starts curving to the north. Irene is forecast to make landfall in the US near Wilmington, NC Saturday evening. However, it is important to note that this is not a definitive forecast, the average forecast error for day 5 is 250 miles. The timing of Irene's recurvature depends on how quickly several small troughs of low pressure in the Northeastern US move to the east. After Saturday, Irene may pose a threat to the mid-Atlantic coastline and locations further north, but it is too early to make a skillful forecast for those regions.

NHC is forecasting for Irene to become a major hurricane (winds faster than 110 mph), within 24 hours, then reaching peak intensity at 130 mph (Category 4 storm) by 8pm EDT Thursday evening.

Forecast models and adaptive observations
The different forecast models are in rough agreement until Irene nears the Carolinas. The dynamical hurricane forecasting models, GFDL and HWRF, have Irene making landfall near Charleston, SC. NGFDL (a variant of the GFDL that uses NOGAPS for background conditions) has landfall near Morehead City, NC, and the GFS has Irene crossing the Outer Banks. The UKMET forecast track splits the difference, placing Irene near Myrtle Beach, SC at landfall.

To reduce the model spread, and improve the track forecast error, the NOAA Gulfstream IV and an Air Force WC-130J have been flying dropsonde missions north of Irene. A dropsonde is an meteorological instrument package dropped from a plane that can tell you the vertical profile of temperature, pressure, moisture, and winds. By flying these missions, the dropsondes can improve all of the numerical weather prediction models initial picture of the atmospheres, which improves the forecast. Also, NHC has asked NWS offices in the southeastern US that launch weather balloons to do so every 6 hours instead of the normal 12 hour frequency.


Figure 2 Official track forecast of Irene as of 2am.

5AM update
The 00Z ECMWF forecast is available and Figure 3 shows the maximum wind speed over the next week for the eastern coast of the US. Green indicates tropical storm force winds, while yellow and orange are hurricane-force winds. The important thing is not to fixate on the predicted landfall location, but to see that Irene's winds will affect areas far away from landfall. The GFS, not shown, agrees with ECMWF that Irene will have a large area of tropical-storm force winds associated with it.

Figure 3 Maximum wind-speed in mph from the 00Z August 23 ECMWF forecast for the next week.

Impacts

In the immediate future, Irene is expected to have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are forecast to reach the southeastern Bahamas and the Turks and Caicos sometime this afternoon or evening. These locations can also expect 5-10 inches of rain. Three to six inches of rain are forecast over northern Hispaniola, with isolated areas receiving up to 10 inches. This could lead to flash flooding and mudslides in mountaineous terrain. NHC is predicting a storm surge of 9-13 feet above normal tide level for the southeastern Bahamas and the Turks and Caicos.

Outside of the islands immediately impacted by Irene, it is my judgement that everybody living on the eastern coast of the US should monitor Irene and review their hurricane preparations over the next few days.

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 earthlydragonfly:


With all of the rain they are getting right now.. Im not really sure they are catching a break. From the winds probably and surge probably... But the rain in the mountains is going to be a real problem with flash flooding and mud slides.


Concur. Haiti has a lot of people living at the base of largely deforested mountains. Any significant rainfall can be quickly converted into a deadly juggernaut of mud and water, racing to the coast. It can wipe out whole villages, or cut off the coastal supply routes. Once the rain stops, the new topography creates pools of standing water, just right for disease vectors.

I don't think there's anyone in Haiti who's feeling too good about Irene just because the imaginary line that the NHC drew didn't cross their landmass…
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So did this move east or west from yesterday?

Quoting charlottefl:
OK, let's try this again 6Z GFS



6Z GFS
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Quoting nash28:


I think this one is gonna be a nailbiter till 24-36hrs out. It's just not cut and dry. It could slam us right up the gut if the weakness isn't as pronounced. It could hit the OBX or it could possibly miss everyone (not likely).


Got that right, Nash. Watching, waiting, getting ready, sending prayers UP for everyone.
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Looks like she is already shifting more north.
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Quoting K8eCane:




Hey...Im shakin too NC. I gotta go to the store later. Aint lookin forward to it. I keep hoping this forecast will go on and shift off the coast. What do you think? Wish it would go ahead so i can get back to normal thinking LOL


some of the models take it off the OBX but we will still see a hard impact even from that scenario with some of the models predicting a Cat 4..I honestly dont see any difference in the models that were aiming at us yesterday before the dropsondes and the models with the dropsondes added to them..the only thing that changed was the GFDL and UK who are aiming at Charleston..
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OK, let's try this again 6Z GFS



6Z GFS
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Suppose, they better pack a lunch. Mine is protected be two German Shepards and bolted down to concrete, hardwired to the house. And, it better be a good freakin' lawn mower....LOL
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Quoting yesterway:


Why do you feel you need to add "just sayin" to your statement?


Why do you care?
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Quoting presslord:
Whatcha think nash?


I think this one is gonna be a nailbiter till 24-36hrs out. It's just not cut and dry. It could slam us right up the gut if the weakness isn't as pronounced. It could hit the OBX or it could possibly miss everyone (not likely).
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Quoting nrtiwlnvragn:


Here is a crude animation that will give you a broad, general idea of steering with various trofs (lows) over the CONUS and high pressure in the Atlantic.


What a cool little animation. I'm aiming storms all over the place!
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Quoting nrtiwlnvragn:


Here is a crude animation that will give you a broad, general idea of steering with various trofs (lows) over the CONUS and high pressure in the Atlantic.


Great link for teaching newbies and kids. I'm bookmarking it to teach my grandkids. Thanks!
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Quoting CarolinaHurricanes87:


Morning. Looks like it'll continue to be an interesting few days for us north carolinians.


yep..I just looked at the ECWMF run and well it has a bullseye right at us..I said yesterday I would leave for a Cat 4 or more and that model has a pressure of 926..if that came to be true, I'm heading inland..
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Quoting msgambler:
Until they run out of gas. Just sayin'


Why do you feel you need to add "just sayin" to your statement?
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06z Dymamic Models (More sophisticated models)

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Quoting msgambler:
Until they run out of gas. Just sayin'


Or worse... some cheeky "so and so" fires up an ol Lawn Mower and pulls a fast one on ya Generator while your snoring...

(True story - heard after Ivan hit Cayman).
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Ok I need to go back to bed the NCEP page is playing tricks on me lol...
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting ncstorm:


not looking good for us here in eastern nc.."shaking like a leaf"..LOL!




Hey...Im shakin too NC. I gotta go to the store later. Aint lookin forward to it. I keep hoping this forecast will go on and shift off the coast. What do you think? Wish it would go ahead so i can get back to normal thinking LOL
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Whatcha think nash?
Member Since: August 13, 2007 Posts: 0 Comments: 10458
Quoting snotly:


Not many people enjoy the very same tropical conditions that create the need to have generators. A few forget that and try and start them indoors (like a closed garage) to stay out of the elements, with very bad consequences.


100% agree
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Quoting FLdewey:
This is going to be a mess for the Bahamas.

Keep on moving cone... keep on moving.


Dewey -

It is going to get busy in your neck of the woods.

Groups of people here loading up surf boards to catch the waves in Indiatlantic and Cocoa.
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Quoting MahFL:
6 flights today. I note the first one into Irene is surface to 10 k feet, and the others into Irene are surface to 15 K feet, anyone know why the difference ?


Generally the stronger the storm the higher they fly.
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Quoting ncstorm:
Good Morning Everyone..



Morning. Looks like it'll continue to be an interesting few days for us north carolinians.
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311. MahFL
Quoting snotly:


Not many people enjoy the very same tropical conditions that create the need to have generators. A few forget that and try and start them indoors (like a closed garage) to stay out of the elements, with very bad consequences.


Frankly the world is a better place without those kind of idiots walking it - imho.
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Quoting charlottefl:
GFS is out:

(Fairly large file)

Link


I clicked on your link and the dates on that are from May?
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Quoting floodzonenc:
I didn't understand it... Was it from May?



I fixed it not sure what happened there...

Link
Member Since: December 18, 2006 Posts: 7 Comments: 2685
No need to cancel E-Fly. What's better than NY in the rain. Ohh yeah, a root canal.....LOL
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Grocery store was a bit of a zoo last night here in Charleston. Essentials flew off the shelves.
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Quoting floodzonenc:
Morning ncstorm, morning all.


Morning... but Ive been on here so long I thought it was noon... LOL
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Quoting floodzonenc:
Morning ncstorm, morning all.


not looking good for us here in eastern nc.."shaking like a leaf"..LOL!
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Quoting earthlydragonfly:


Most generators will run fine in the rain anyway.


Not many people enjoy the very same tropical conditions that create the need to have generators. A few forget that and try and start them indoors (like a closed garage) to stay out of the elements, with very bad consequences.
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Quoting lennykat4:




Okay, so on here early with lots of good explanations for us learning/lurkers....

...I have to ask a real rookie question.

How, specifically, does that subtropical ridge control the steering of the storm either east or west? Also, if the storm slows or stalls and doesn't encounter the ridge what does that do to the forecasted track?

My apologies for the freshman like questions- just trying to learn how these things work. Thanks for all the great explanations from you guys.


Here is a crude animation that will give you a broad, general idea of steering with various trofs (lows) over the CONUS and high pressure in the Atlantic.
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Good morning friends,

Last weekend SE Florida was in the center of the cone, just 2 days later we are now out of the cone..

Again my old saying... 5 days out the center is where you want to be ..because they always change and move further east or west.

Taking a deep breath for SE Florida and the Keys....

but will watch for all you in North Florida, Georgia and the Carolinas....

Good to see a lot of the old timers here this morning.
I have some errands but will be back!

Gams
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What happened to recon? They were broadcasting, and had almost cleared PR, and now have not had a report in 30 minutes.
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Quoting spayandneuter:
For those that may have to evacuate, please take your pets with you when you leave. If it's not safe to leave a 3 yr old child behind, it's not safe for your pets.

Part of my job is go in and rescue pets after disasters and it's just heartbreaking to see the trauma they go through. Even more heartbreaking to see animals that have died from being left behind tied in a yard or drowned inside their crate with no escape. Those images haunt me and no pet should have to suffer that. It's not a pretty picture, but it's the truth and sadly we see it time and time again. There is no reason to leave them behind. Please take them with you when you leave!

Start making your arrangements now. Here is a link to some helpful info:

Link


Bless you and your work of mercy and compassion.....
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Quoting spayandneuter:
For those that may have to evacuate, please take your pets with you when you leave. If it's not safe to leave a 3 yr old child behind, it's not safe for your pets.

Part of my job is go in and rescue pets after disasters and it's just heartbreaking to see the trauma they go through. Even more heartbreaking to see animals that have died from being left behind tied in a yard or drowned inside their crate with no escape. Those images haunt me and no pet should have to suffer that. It's not a pretty picture, but it's the truth and sadly we see it time and time again. There is no reason to leave them behind. Please take them with you when you leave!

Start making your arrangements now. Here is a link to some helpful info:

Link


Nice post!
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Quoting msgambler:
Morning lil brother...Hope all are well in Sunny Florida


Pretty good except for the little storm that had us in the cone for a couple of days... Glad its moving on but wish for a fish so the fine folks up north would be safe. I might have to cancel a trip up to NY next week.
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GFS is out:

(Fairly large file)

Link
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting leelee75k:
I think coastal areas of Broward and Palm Beach will get Tropical Storm Watches later today... if the storm's tropical windfield is 200 miles wide and she is 100 miles off the coast at her closest approach to us, then it could be expected that some areas will get tropical storm conditions hence the watch/warnings might be necessary.


For once being in South Dade is good. Although we said that before Andrew too...

I still do not think that this will be a Florida Storm, but until Irene is gone I will keep a weary eye on her.
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292. MahFL
6 flights today. I note the first one into Irene is surface to 10 k feet, and the others into Irene are surface to 15 K feet, anyone know why the difference ?
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For those that may have to evacuate, please take your pets with you when you leave. If it's not safe to leave a 3 yr old child behind, it's not safe for your pets.

Part of my job is go in and rescue pets after disasters and it's just heartbreaking to see the trauma they go through. Even more heartbreaking to see animals that have died from being left behind tied in a yard or drowned inside their crate with no escape. Those images haunt me and no pet should have to suffer that. It's not a pretty picture, but it's the truth and sadly we see it time and time again. There is no reason to leave them behind. Please take them with you when you leave!

Start making your arrangements now. Here is a link to some helpful info:

Link
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Good Morning Everyone..

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Quoting charlottefl:


There are different steering layers, or (heights) for different strengths of storms. High pressure systems always steer storms in a clockwise flow. If you look at the image below. Irene is at the Western periphery of the AB ridge over the Atlantic. The flow there changes from due West to between WNW-NW. She should continue moving WNW-NW until she reaches the end of the ridge where the gap between the two highs in. The exception to this would be if the AB Ridge would build West, or if the trough was deeper than expected, forcing either a more westward track, or a sharper turn N, and then E. Hope that helps ;)

Link



Thank you SOOOO much. This is exactly the kind information I'm hoping to find on here.
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Morning lil brother...Hope all are well in Sunny Florida
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Quoting msgambler:
E-Fly, I got mines. Got 300gals. ready to go and another (6) 5 gal. cans we fill when one approaches.


Mornin Gambler
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Quoting dan77539:
Let's just say that at least Haiti is finally catching a break! Another natural disaster would have just added insult to injury.


With all of the rain they are getting right now.. Im not really sure they are catching a break. From the winds probably and surge probably... But the rain in the mountains is going to be a real problem with flash flooding and mud slides.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.