Dangerous Tropical Storm Irene headed for the Dominican Republic

By: Dr. Jeff Masters , 2:38 PM GMT on August 21, 2011

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Tropical Storm Irene roared into life last night, transitioning from a tropical wave to a 50 mph tropical storm in just a few short hours. Irene is getting organized quickly, and has the potential to become a hurricane by Monday morning. All interests in the Dominican Republic, Haiti, Cuba, the Bahamas, and South Florida should prepare for the arrival of this dangerous storm. An Air Force hurricane hunter aircraft in the storm found the strongest winds near 18°N latitude to the north of Irene's center at 8am this morning. After passing through the center, the plane returned to the area of strongest winds two hours later, and found that flight level winds at 5,000 feet had increased by about 5 - 8 mph. However, the pressure in the latest center fix taken at 10am EDT remained the same as two hours previously, 1007 mb, and the plane noted that Irene's center was not circular, signs that the storm still has some work to do before serious intensification can begin. Visible satellite loops and radar out of Martinique show the storm has rapidly organized this morning, with well-developed spiral bands forming and a large area of intense thunderstorms to the north of the center. Irene has shrugged off the dry air that was bothering it yesterday, and wind shear has fallen to the low range, 5 - 10 knots, as analyzed by the University of Wisconsin CIMSS group. Torrential rains and strong gusty winds are affecting the northern Lesser Antilles this morning. A wind gust of 41 mph was recorded at St. Eustatius at 8am local time.


Figure 1. Morning satellite image of Irene.

Track forecast for Irene
The computer models are in agreement that Irene will pass just south of Puerto Rico tonight, then hit the south coast of Hispaniola in the Dominican Republic or Haiti on Monday afternoon. Irene should then emerge into the channel between Haiti and Cuba on Tuesday afternoon, when the storm will have 12 or so hours over water before having to contend with Cuba. A trough of low pressure is expected to move across the Eastern U.S. on Wednesday and Thursday, turning Irene to the northwest and north by Thursday. The timing and strength of this trough varies considerably from model to model, and will be critical in determining where and when Irene will turn to the north. Irene's strength will also matter--a stronger Irene is more likely to turn northward earlier. The most likely path for Irene is a track just east of the Florida Peninsula and into Georgia, South Carolina, or North Carolina by next weekend, but a landfall near Miami then directly up the Florida Peninsula is also a reasonable solution--like Tropical Storm Fay of 2008 did. Fay formed just off the coast of Puerto Rico, and was never quite able to get organized enough to become a hurricane, due to passage over Hispaniola and Cuba. Fay topped out as a strong tropical storm with 70 mph winds, and did over $500 million in damage in the U.S., mostly due to flooding rains in Florida that accumulated to over 25 inches in a few areas. Fay also dumped heavy rains on Hispaniola, triggering flooding that claimed eight lives.


Figure 2. Track of Tropical Storm Fay of 2008.

Intensity forecast for Irene
Irene is embedded in a large envelope of moisture now, and wind shear will remain low, 5 - 10 knots, for the next five days. With water temperatures very warm, 28 - 30°C, these conditions should allow for intensification except when land is interfering. Irene's current appearance on satellite loops gives me the impression of a storm that is not fooling around, and I expect Irene will be a hurricane before hitting Hispaniola on Monday. Passage over Hispaniola will not destroy Irene, since it is a fairly large storm. Once the storm finishes with Hispaniola, it will have to deal with Cuba, which will keep Irene from intensifying significantly. Once Irene pops off the coast of Cuba Wednesday or Thursday into the Florida Straits, Irene will likely be a tropical storm. If the storm then has at least a day over water before hitting land, it will likely become a hurricane again, and could become a major hurricane if it ends up missing South Florida and moving over the warm waters on either side of the Florida Peninsula.

Harvey hits Belize
Tropical Storm Harvey made landfall at 2pm EDT on Saturday near Dangriga Town, Belize, as a tropical storm with 60 mph winds. Harvey continues to dump very heavy rains on southern Mexico, but dissipation is expected tonight as the storm pushes inland. Harvey was a small storm, and the strongest winds were confined to a short stretch of coast near where the center came ashore. Winds at Belize City, Belize on Saturday topped out at 15 mph.


Figure 3. Radar image of Harvey taken at 11:30am EDT on Saturday, August 20, 2011, a few hours before landfall in Belize. A small closed eye is visible just south of the offshore islands of Belize. Image credit: Belize National Meteorological Service.

Invest 98L northwest of the Cape Verde Islands
A tropical wave few hundred miles northwest of the Cape Verde Islands off the coast of Africa, Invest 98L, has become disorganized and lost most of its heavy thunderstorms. The disturbance is moving over colder waters and encountering drier air, and NHC is giving 98L only a 10% chance of developing into a tropical depression by Tuesday. The latest set of model runs keep 98L well out to sea away from any land areas over the next five days.

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Long-range radar out of Puerto Rico

Jeff Masters

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Quoting kmanislander:
St Croix has round two of nasty weather on the way as they get the SE quad. Hope they don't think its over.


I'm listening to a St Croix radio station...they know it's comin'
Member Since: August 13, 2007 Posts: 0 Comments: 10492
3722. Levi32
Of note is that the 12z CMC ensemble mean favors a track into Florida, significantly farther west than the operational run.

96 hours:

Member Since: November 24, 2005 Posts: 635 Comments: 26699
3721. Speeky
Who thinks that Irene may hit one of the Carolinas as a major hurricane?
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Quoting Seflhurricane:
by how much ??? closer to florida


It only shifted a bit eastward on the 5 P.M. advisory anyways..
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St Croix has round two of nasty weather on the way as they get the SE quad. Hope they don't think its over.
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3716. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129444
Quoting Levi32:


NFC East? I probably am a fan of the Eagles more than the darned Cowboys. Let's put it that way.


I hear the Eagles are undergoing Rapid Intensification. Watch out.
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Quoting Seflhurricane:
by how much ??? closer to florida


The HWRF is almost exactly the same as the last run, if not slightly farther east.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Yep, Myrtle Beach is possible target now. 126 and final image.
Member Since: August 1, 2011 Posts: 28 Comments: 8046
Quoting USAFwxguy:


agree... but the GFS and EURO are trending that way.


Yes but they can only trend east for so long..
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Quoting MiamiHurricanes09:
Quite the shift westward on the 18z HWRF (126 hours):

by how much ??? closer to florida
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3709. Dakster
Quoting dfwstormwatch:

actually it will be eastward and more northward landfalll...


--- YES I agree, I got that mixed up! --
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3707. WxLogic
Quoting charlottefl:


Yeah I realize that, but there is a pretty significant weakness there now, with an approaching trough, was just trying to show the intensity of the storm affects the track a good deal.


True...
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Quoting Hurricanes12:


Stay safe.
Yes and who knows when it will be back,... a very dark stormy night, in the Island of the enchantment...
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Turned slightly toward Myrtle Beach. 930 mb storm at 120 hr.

Member Since: August 1, 2011 Posts: 28 Comments: 8046
3704. Levi32
It almost looks like Irene may be slowing down a bit as new convection fires up a strong band just to the east of the center, which is trying to form into a partial eyewall. The center looks like it may be hanging back towards that intense band a bit and slowing down.
Member Since: November 24, 2005 Posts: 635 Comments: 26699
Quoting Dakster:
I bet we have a slight westward shift with the 8pm advisory...


Tracks don't change on the intermediate advisories.
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Quoting Dakster:
I bet we have a slight westward shift with the 8pm advisory...


The cone doesn't change in the 8am/pm and 2am/pm advisories.
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Quoting Dakster:
I bet we have a slight westward shift with the 8pm advisory...


With the 18Z models still showing an eastward shift? Not likely.
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Quoting Dakster:
I bet we have a slight westward shift with the 8pm advisory...


Probably not since the track isn't updated at 8pm. :-P
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting Dakster:
I bet we have a slight westward shift with the 8pm advisory...

actually it will be eastward and more northward landfalll...
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3697. hahaguy
Quoting USAFwxguy:


Yes.


Yes to which one? lol
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Slight shift westward on the 18z HWRF (126 hours):

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Thanks for this info. Hispaniola is the sticky spot and possible game changer.
Quoting kmanislander:


If you mean the mountains in PR no effect IMO as PR is too small an island to do much damage to the circulation which is pretty well established now. Sinking air warms and dries as it sinks and that would not be good for a tropical system but I don't see that as an issue here.

Hispaniola is a different story altogether. Several issues there with very high terrain near 10,000 feet. Passage over that island for any appreciable period of time could decouple the storm. Even a close pass near the coast could disrupt the circulation on that one side due to interaction with land and friction.
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Well at home in Isabela PR waiting the arrival of Irene, will be my 5th storm in my 31 years of live wind is starting to increase, stay safe people.
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3692. Dakster
I bet we have a slight westward shift with the 8pm advisory...
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poor Charleston
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Quoting Bluestorm5:
Gulf Stream is taking affect. 926 mb storm toward Charleston at 114.

this has nothing to do with the gulf-stream...
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Quoting USAFwxguy:


I have noticed that CONUS high backing off while the ATL high gains a bit of ground. In fact new high center nne of Irene at the low lvls.


Yes, that is what I was referring to.
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Quoting WxLogic:


Well... not actually doing it at this time period, that's the thing we have to keep in mind. For the time period it starts to basically move NW to NNW or so is a lot later so the steering map would look quite different.


Yeah I realize that, but there is a pretty significant weakness there now, with an approaching trough, was just trying to show the intensity of the storm affects the track a good deal.
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Possible Hurricane Hugo Part 2.
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Quoting Bluestorm5:
Gulf Stream is taking affect. 926 mb storm toward Charleston at 114.



Isn't that a Cat 5, oh god.
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3685. jonelu
Quoting Tropicsweatherpr:


I am going to go offline as for sure power will be turned off by sections in PR as it occured in past events of landfall here.I am safe in my house with shutters. See you and the rest when power is back.
Good luck. Be safe
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Quoting USAFwxguy:


You got that bass ackwards.
what the hell, it works either way...
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Quoting USAFwxguy:


Yeah....recurve not out of question. CONUS could still be off the hook with the way these models are trending.


It won't recurve, ridge is too far west for it to go OTS.
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3682. Relix
Power holding steady in Toa Baja, PR. Gusty finally some light rain. I am ready! Just bring it Irene I wanna enjoy the show :D!
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Gulf Stream is taking affect. 926 mb storm toward Charleston at 114.
Member Since: August 1, 2011 Posts: 28 Comments: 8046
stay safe i lost power
Member Since: July 21, 2010 Posts: 60 Comments: 1011
Are they sending another plane today ?
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Quoting yesterway:


Good advice.

Plus if it comes anywhere near the gulf, they'll use that as an excuse to raise gas prices. Happens everytime a storm so much as sneezes near the rigs:)
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Nitey-nite, Irene

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Quoting TropicalAnalystwx13:


Nope, you aren't crazy.

Yay.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
3674. Thrawst
Quoting Levi32:


If you're in the Bahamas you better be ready for a storm as soon as possible.


We stocked up on milk :D and the most important water as well. School will likely be out starting wednesday and through friday. 5 day weekend for the first week of school... ... nice.
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3673. 7544
Quoting Seflhurricane:
8pm Advisory should be out in 30MIN looking for winds to increase and additional watches


too early for fla watches thos right
Member Since: May 6, 2007 Posts: 0 Comments: 6874

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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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