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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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
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Quoting Bluestorm5:
929 mb storm at 108 hr out. Still going toward Charleston and about to run over Gulf Stream. Uh-oh.


Doesn't look like a recurve to me, I can see this heading for the Carolinas.
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3671. Levi32
Quoting kmanislander:


No question about that. The second key is whether Irene passes to the S of PR, which I think it will do , as Hispaniola is farther N which would bring into play a pass right on the S coast of that island. If that were to happen it might weaken Irene enough for it to push all the way to the Western tip of Haiti.

All conjecture for now but not off the table IMO as the ridge has been reinforced late today which probably accounts for the track flattening out the past few hours.


I think a due west track all the way to southwest Hispaniola is asking too much, but we will see. A lot depends on where it strikes the island.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting Bluestorm5:
Runned into cold water I think, but this system is ACTING like Hugo. 102 hr.
Wut cold water LOL. Its still at 928mb thats stong cat 4 or cat 5.
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Eye is tightening....or the center if you prefer...
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Quoting jennT:


sure. it seems to be the eye. but it's been pretty dang still on blue mtn all day.
well be careful, you will know in a few minutes if it is.
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3666. 7544
remember when katrina made that sw jog and look what happen
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3665. hahaguy
So should expect more eastward shifts or maybe a few westward shifts?
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Quoting TropicalAnalystwx13:


That was different though - Alex was of monsoon origins, like Western Pacific systems. Irene is a genuine system, and so the winds and pressure should stay close together in tandem.



What's the difference? If it's from monsoon origins or a twave off africa? I mean a Hurricane/TS is a Hurricane/TS, correct? They still operate the same way? I'm not being sarcastic, just asking because I don't see what the difference is. What makes one Genuine and not the other?
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there is a legendary cruiser's bar in Jost van Dyke called Foxy's...I suspect it's packed right now ...with intoxicated sailors...
Member Since: August 13, 2007 Posts: 0 Comments: 10492
929 mb storm at 108 hr out. Still going toward Charleston and about to run over Gulf Stream. Uh-oh.
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3661. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129902
3659. DVG
>Looks like it is just to the south of the western tip of St. Croix>

the dvorak I think is working best for visual clues at the moment
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Quoting Levi32:


Hispaniola probably holds the biggest key to Irene's future. It may determine what her maximum intensity could be, which would then also affect her track.


No question about that. The second key is whether Irene passes to the S of PR, which I think it will do , as Hispaniola is farther N which would bring into play a pass right on the S coast of that island. If that were to happen it might weaken Irene enough for it to push all the way to the Western tip of Haiti.

All conjecture for now but not off the table IMO as the ridge has been reinforced late today which probably accounts for the track flattening out the past few hours.
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After Irene's movements, the 18 Z top 10 analogs changed:
http://moe.met.fsu.edu/~acevans/models/al092011_a nalogs.png

Not that I see a track anything like it, but that J-storm from 04 is on the list...
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3655. HCW




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3654. WxLogic
Quoting charlottefl:


Well that make sense if it gets to that pressure: (not so sure I can see that happening tho)



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.
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3653. jennT
Quoting Clearwater1:
Maybe because you are in the Eye?


sure. it seems to be the eye. but it's been pretty dang still on blue mtn all day.
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caller said since the water is so deep around st croix storms like to spin up right over them the senator kind of blew the caller off but isnt that what we are seeing
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8pm Advisory should be out in 30MIN looking for winds to increase and additional watches
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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.
Thank you.
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3649. 7544
what does this sw jog mean in term of the track bad or good for fla tia
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Quoting JLPR2:
Well, I'm going to say goodbye, power is flickering. :\

Irene has not arrived and the power is already failing.


Stay safe.
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Runned into cold water I think, but this system is ACTING like Hugo. 102 hr.
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3645. ackee
IT really does look like IRENE is movin SSW on the radar LETS see how long this will continue
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Quoting Levi32:
A short-term due west jog does look to be ensuing on radar. It will be interesting to see if it stays that way and doesn't actually make landfall in PR. Regardless, Puerto Rico will get the worst of Irene, either way.


and that's the sad part, they're going get it either way now looks like:(
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Quoting Bluestorm5:
someone was posting at first... anyway... onward to Charleston O_O





ouch 925mb
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
3641. JLPR2
Well, I'm going to say goodbye, power is flickering. :\

Irene has not arrived and the power is already failing.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting WeatherNerdPR:

Call me crazy, but it seems to have slowed down.
I think so too,it has been over St.Croix for the past three hours...
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Quoting MississippiWx:


apparently that's a big eye
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Quoting Bluestorm5:
938 mb storm on eastern side of Bahamas.
post 3572 you said it was south of the Bahamas, now you are saying east ????
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someone was posting at first... anyway... onward to Charleston O_O
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3636. Levi32
Quoting Thrawst:


Ahhhh :/ so this means that Nassau is more in the path of the eye of a hurricane now? If so, I'll tell my parents to help me start getting the shutters down tomorrow or Tuesday.


If you're in the Bahamas you better be ready for a storm as soon as possible.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
3635. WxLogic
Quoting Seflhurricane:
the NHC says its an outliner bu hasnt the HWRF always overdone systems in strength


Yeap... is sure has. In past days it hasn't been doing to bad but for some reason is acting up again.
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Quoting WxLogic:
HWRF want to go out to sea from the looks of it



Well that make sense if it gets to that pressure: (not so sure I can see that happening tho)

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Member Since: July 15, 2006 Posts: 17 Comments: 10284
3632. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129902
18z GFS has a 105kt 978 millibar cane hitting the Georgia/SC coast late on Friday.

Link
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it is moving west lol and willl be a cane by 11pm
just a opinion!!!!!!!!!
Member Since: August 17, 2011 Posts: 0 Comments: 22
3628. MahFL
On the radio they have a report of the east eyewall is intensifying, matched by the radar image.
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Quoting WxLogic:
HWRF want to go out to sea from the looks of it

the NHC says its an outliner bu hasnt the HWRF always overdone systems in strength
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3626. Thrawst
Quoting TropicalAnalystwx13:


Recon found a minimum central pressure so far of 995.4 mb. This means that the winds are likely around 60 mph, from what they have found so far. However, that is still a little low given the pressure, and further strengthening should occur tonight. Given its current heading, a direct landfall on Puerto Rico my mid-morning tomorrow is likely. After that, it seems that Irene will only scrape the northern coast of Hispaniola rather than cross the entire length. This means that we could be dealing with a stronger system in the long run.

Another thing to note is that, since Irene is farther north than originally predicted, the models have shifted more towards South Carolina and North Carolina.


Ahhhh :/ so this means that Nassau is more in the path of the eye of a hurricane now? If so, I'll tell my parents to help me start getting the shutters down tomorrow or Tuesday.
Member Since: July 18, 2010 Posts: 50 Comments: 1909
3625. Levi32
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.


Hispaniola probably holds the biggest key to Irene's future. It may determine what her maximum intensity could be, which would then also affect her track.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting TropicalGenesis:
Looks like Irene is slowing down a bit.
That may mean that Irene is really starting to get itself together.
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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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