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 weatherguy03:


Yes. I say that carefully..LOL I said a few days ago that Irene was not going into the Eastern GOM and I almost got crucified by the Tampa Wishcasters!..LOL

Indirect affects along the East Coast of gusty winds, beach erosion and high surf.


I wish the wishcasters could have the damn thing!
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Good Mid-Morning all. Time to focus. Looks like my friends in Wilmington will be pulling up the boats and doing a lot of work soon, spoke to them yesterday. Points north looking not so good, as well as a lot of the storm will stay on shore, even it if gets bumped back out. This one is starting to look serious. Plenty of time yet to be prepared. The growth in size of this one through the next 12-36 should be amazing.
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Irene's core tightening even more! Get ready for the eye...
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Quoting K8eCane:



Can I count on you to let me know about the model runs and the significance of them. ?


We all count on his input - BTW, 03, thanks for all the time/ energy you put into the board. :)
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Quoting alvarig1263:


Still variables involved that could shift the track significantly. Just keep an eye out for at least the next couple days. I'm in Naples, FL and I'm still watching Irene just in case. Don't want a Cat. 4 to catch you off guard.


I'm in Sarasota and doing the same thing. Watching and waiting to see if and when she turns away. Having family and friends up the east coast and in NC keeps me watching too.
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Quoting K8eCane:



Can I count on you to let me know about the model runs and the significance of them. ?


Yes watch my video and blog update this evening.
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charlottefl
Quoting Nolehead:
morning, still think the models will go back west before it's said and done...remember how many storms have done this before?? no way am i wishcasting at all...surf will be there anyways...but just wait and see..


I don't think there will be any major shifts from here on out. But just a small motion further to the west, or earlier to the north makes a big difference as to where this comes in because of the way the coastline in the SE is angled.


could be very true, but you know just as well how many storms do what they want to do is all i'm saying...it's far from over i believe..could be wrong and more than likely am..but let's just wait and see what she has in store..
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Quoting presslord:


CRS promised to keep us posted if he can...


As is my nature, I am crying for the Turks, Caicos and Bahamian Islanders.
It's gonna be rough.
On the upside, they are experienced at such things and will be able to bear these conditions better than most.
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Quoting weatherguy03:


Decision day for North and South Carolina will be tomorrow. We will get a good idea after the model runs today.



Can I count on you to let me know about the model runs and the significance of them. ?
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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.


May be crude but it explained the concept well - at least to me. Thanks.
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Quoting stillwaiting:
sooo flloridas officially out of the woods for direct impacts from irene,the west coast of fl 100% clear no???


Yes. I say that carefully..LOL I said a few days ago that Irene was not going into the Eastern GOM and I almost got crucified by the Tampa Wishcasters!..LOL

Indirect affects along the East Coast of gusty winds, beach erosion and high surf.
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i cant remember the ast time any model shifted west w\irene,im thinking fish storm!!!,but dont tell that to those i the bahamas
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Quoting stillwaiting:
sooo flloridas officially out of the woods for direct impacts from irene,the west coast of fl 100% clear no???


Still variables involved that could shift the track significantly. Just keep an eye out for at least the next couple days. I'm in Naples, FL and I'm still watching Irene just in case. Don't want a Cat. 4 to catch you off guard.
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the key element for south florida is if Irene stays on the current track we would only see 35-40 mph winds with alot of rain if the turn does not occur around grand inagua then we will receive stronger winds and rain
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Quoting Chicklit:
Turks and Caicos next in line for Irene.


CRS promised to keep us posted if he can...
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Turks and Caicos next in line for Irene.
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sooo flloridas officially out of the woods for direct impacts from irene,the west coast of fl 100% clear no???
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Quoting Tazmanian:
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT TUE AUG 23 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
IRENE LOCATED ABOUT 70 MILES SOUTH-SOUTHEAST OF GRAND TURK ISLAND.

SHOWERS AND THUNDERSTORMS NEAR A LARGE LOW PRESSURE SYSTEM LOCATED
ABOUT 750 MILES WEST-NORTHWEST OF THE NORTHERNMOST CAPE VERDE
ISLANDS HAVE CHANGED LITTLE IN ORGANIZATION. WHILE THE LOW IS
MOVING WEST-NORTHWESTWARD AT ABOUT 15 MPH TOWARD WARMER
WATERS...UPPER-LEVEL WINDS ARE FORECAST TO BECOME LESS FAVORABLE
FOR DEVELOPMENT. THIS SYSTEM HAS A LOW CHANCE...20 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

A LARGE LOW PRESSURE AREA IS CENTERED ABOUT 300 MILES SOUTHEAST OF
THE CAPE VERDE ISLANDS. ALTHOUGH THIS SYSTEM IS NOT CURRENTLY WELL
ORGANIZED...UPPER-LEVEL CONDITIONS FAVOR SOME DEVELOPMENT DURING
THE NEXT SEVERAL DAYS. THIS SYSTEM HAS A LOW CHANCE...20
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES TO THE WEST AT ABOUT 10 MPH.


ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.



looks like we have 90L soon


90L is up on the Navy Page now
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413. HCW
90L from the NHC

Member Since: August 10, 2002 Posts: 0 Comments: 1406
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.


Thanks so much-- that was exactly what I needed. Not to mention it was kind of fun ;)
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We will be interested to see what 90L does...Post 369 already explained what may happen.

Be back this afternoon.
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It's been a long time since all the islands of the Bahamas has been hit by a single hurricane the size of Irene. I fear if Nassau takes a direct hit it will be very difficult for the government to get help to the family islands.
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Quoting Nolehead:
morning, still think the models will go back west before it's said and done...remember how many storms have done this before?? no way am i wishcasting at all...surf will be there anyways...but just wait and see..


I don't think there will be any major shifts from here on out. But just a small motion further to the west, or earlier to the north makes a big difference as to where this comes in because of the way the coastline in the SE is angled.
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting K8eCane:



Thank GOD Bob..when will we know this?


Decision day for North and South Carolina will be tomorrow. We will get a good idea after the model runs today.
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Recon plane hasn't sent an HDOB for over an hour. Something's up.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting weatherguy03:


I may shift alittle farther East later today as I am thinking the model consensus may shift alittle farther East. We will see.



Thank GOD Bob..when will we know this?
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Quoting charlottefl:


Wow, that's all I have to say about that...


Yeah, not good.

Quoting NICycloneChaser:


Absurd amount of moisture out there. The waves are going to start firing up early, methinks.


Yeah, and we're about to enter September too...
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Hurricanes follow only one law and it is the law of physics. They only follow 1 rule, find the path of least resistance to start moving north, and they serve one purpose, to cool the overheated waters of the tropics. Any mention of it turning south or due west as well as intensification has to be backed up by these rules. Other factors such as land interaction also affect, but mainly the rules mention above still apply.
Member Since: August 1, 2007 Posts: 0 Comments: 167
It's crazy how for DAYS the GFS had Irene hitting anywhere from Texas to Florida along the Gulf coast and then all of sudden it changes it's mind and turns it out to sea. That's why here in South Florida I'm keeping watch just to make sure Irene doesn't head my way with my guard down.
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Looks like a SAL less environment.. 
Quoting TropicalAnalystwx13:
Well, this is unusual.


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Quoting yesterway:


I see it being used a lot lately and I am not sure what the purpose is. That's all..


Some people apparently have seen too much Bill Engvall. He uses it a lot in his routines.
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Quoting TropicalAnalystwx13:
Hello 90L:

BEGIN
NHC_ATCF
invest_al902011.invest
FSTDA
R
U
040
010
0000
201108231157
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 90, 2011, DB, O, 2011082306, 9999999999, , , , , , METWATCH, , AL902011
AL, 90, 2011082306, , BEST, 0, 122N, 190W, 25, 0, DB, 0, , 0, 0, 0, 0,
Another low rider.
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Quoting leelee75k:


I think "just saying" is another way of saying "imo" "or in my opinion". Many people use these to clarify their posts as being their opinions/thoughts when trying to not be argumentative or confrontational when giving an opposing opinion of an issue.

now back to the tropics!


I see. Thank you.
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It's crazy how for DAYS the GFS had Irene hitting anywhere from Texas to Florida along the Gulf coast and then all of sudden it changes it's mind and turns it out to sea. That's why here in South Florida I'm keeping watch just to make sure Irene doesn't head my way with my guard down.
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morning, still think the models will go back west before it's said and done...remember how many storms have done this before?? no way am i wishcasting at all...surf will be there anyways...but just wait and see..
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Quoting TropicalAnalystwx13:
Well, this is unusual.



Absurd amount of moisture out there. The waves are going to start firing up early, methinks.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting yesterway:


I see it being used a lot lately and I am not sure what the purpose is. That's all..


I think "just saying" is another way of saying "imo" "or in my opinion". Many people use these to clarify their posts as being their opinions/thoughts when trying to not be argumentative or confrontational when giving an opposing opinion of an issue.

now back to the tropics!
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Quoting weatherguy03:


I am. I will be more confident after the 12Z model runs come out later. As I was mentioning yesterday the 0Z runs last night and the 12Z runs today will go a long way in smoothing out the track with the Upper Air Data. Right now out of respect for the HWRF and GFDL models I am from Myrtle Beach, SC to North Carolina OBX. I will go from there later. I will have a video and a blog out this evening.


I may shift alittle farther East later today as I am thinking the model consensus may shift alittle farther East. We will see.
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Quoting ecupirate:


My house is now directly under an "m" circle....

I hope this thing shifts further east! Im glad I took care of all my preperations yesterday. Looks like panic mode is setting in for ENC today.


I just wish i knew what emergency mgt plans to do for shelters if needed, etc...a lot rides on this forecast for me and my son and my animals
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Quoting TropicalAnalystwx13:
Well, this is unusual.



Wow, that's all I have to say about that...
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting ecupirate:


My house is now directly under an "m" circle....

I hope this thing shifts further east! Im glad I took care of all my preperations yesterday. Looks like panic mode is setting in for ENC today.


:-0
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Quoting weatherguy03:


I am. I will be more confident after the 12Z model runs come out later. As I was mentioning yesterday the 0Z runs last night and the 12Z runs today will go a long way in smoothing out the track with the Upper Air Data. Right now out of respect for the HWRF and GFDL models I am from Myrtle Beach, SC to North Carolina OBX. I will go from there later. I will have a video and a blog out this evening.


Mucho thankso!!
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Quoting presslord:


You pretty confident in the forecast track at this point?


I am. I will be more confident after the 12Z model runs come out later. As I was mentioning yesterday the 0Z runs last night and the 12Z runs today will go a long way in smoothing out the track with the Upper Air Data. Right now out of respect for the HWRF and GFDL models I am from Myrtle Beach, SC to North Carolina OBX. I will go from there later. I will have a video and a blog out this evening.
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Well, this is unusual.

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My house is now directly under an "m" circle....

I hope this thing shifts further east! Im glad I took care of all my preperations yesterday. Looks like panic mode is setting in for ENC today.
Member Since: Posts: Comments:

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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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