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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Floater - RGB Color Infrared Loop
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting scottsvb:


That data wont help much till Weds when its near Cuba-Bahamas cause of the trough moving out.. we need to see how much ridging builds back in over the bahamas



Any actual upper air data is good data to feed into the models and will help decrease uncertainty...

And yeah, by Wednesday we obviously will have a better idea where this is going. By then it'll be IN the Bahamas.
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So looks like the HWRF and GFS have it off to the right... Wonder if the GFDL will switch over.
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Quoting TropicalAnalystwx13:
It stalled over the Gulf Stream...



it just keeps getting better
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Quoting TropicalAnalystwx13:
Got a feeling its coming here on this run...



OMG...is that a 914 mb cane off the southeast...what model is that?!

This would be the biggest east coast storm (including my area) if that crap happened....WOWZA
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um, wow... strong storm toward East Coast on this run. I will continue posting it.
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It stalled over the Gulf Stream...

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This setup is interesting for sure:

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Quoting TropicalAnalystwx13:
Got a feeling its coming here on this run...




looks like NC is in for a powerfull storm
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Quoting TropicalAnalystwx13:
Got a feeling its coming here on this run...

Might go for GA.
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GFS is always a little right biased
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612. MZT
The tracks are shaping up more and more as an Isabel/Floyd scenario. Not that it has to land in N.C., so much as it could feasibly land anywhere from FL to NC... The newscasters will be all over it, and many people will be worried.
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Got a feeling its coming here on this run...

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Quoting TropicalAnalystwx13:




eeeeeeeeeeeek
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105 hrs...

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Dvorak more centered every frame lately.


2km Storm Relative IR Imagery with BD Enhancement Curve

Member Since: July 3, 2005 Posts: 421 Comments: 127664
I have to keep reminding myself that the gfs and others are only just that, models, and not the exact track, however they are quite compelling.

Edit, But could have FL dodged this one? At the sad expense of the east coast us. Sorry, rather see it do a really sharp right all together
Member Since: August 26, 2006 Posts: 0 Comments: 1547
Quoting emcf30:




Your post I think shows the 2 possible scenarios...

The top (HWRF) if Irene can pass just N of Hispaniola unscathed... the bottom (GFDL) is what happens if this broad center goes through Hispaniola....
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Quoting presslord:
yes...please point out for us the humor in a tropical system striking this

:'(
So sad...
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Still one of my favorite vids.
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Quoting coffeecrusader:
What time does Levi wake up. It would be nice to get an analysis from someone who is educated and not a wishcaster. Its amazing watching this board....

Its going to Miami (guess what their from Miami)
Its going to North Carolina (from NC)
Its going to the Panhandle (from Pensacola)
Its going to Texas (from Texas)

get the picture
Well, from NOLA and, umm, I hold a degree on the subject.

It IS going to Florida, though it may miss to the east.

Almost certain that it will not enter the gulf.

Intensity is highly dependent on the time spent over land and the nature of that land (mountains, etc.). Is possible that a strong TS or cat 1 shows up in FL, or a cat 3 . Just my opinion, but stronger favors a more eastern track (very bad for the Bahamas) as that would mean a miss on most of the mountainous terrain in Hispaniola. Atmospheric conditions and ocean heat content are favorable.

I wish we could nail it down better right now.

As to whom to pay attention to, Levi is a good one, Drakoen knows his stuff, WxLogic is adept and no wishcaster, Dakster, P451, Grothar, scottsvb (with credentials, I think), MiamiHurricane09, and many others I am forgetting at the moment.

Ultimately, pay close attention to the NHC statements and your local NWS office. Their mission is specifically to give you what you need to make decisions in the preservation of life and property. You'll only get a few hours lead on what they will say here, without the wild fluctuations and chaff.
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The eastward trend continues on the latest GFS.

Member Since: March 19, 2009 Posts: 0 Comments: 1421
Quoting stillwaiting:
,that would leave no option other than directly nw into sefl??


That would keep it at a WNW track for a bit before it begins to head into the weakness as it strengths over the Bahamas.
Member Since: October 28, 2006 Posts: 57 Comments: 29934
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597. 7544
lloks like a big turn coming east
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@84HR GFS is in close agreement with NAM on position of High/Lows.



Would still see a WNW in the next couple hours before a turn to the NW close to the FL SE coast start coming to.
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595. JRRP
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GFS...NOW misses florida and sensds a major up the central bahamas. Big east shift......never crosses cuba...stays north
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Quoting TropicalAnalystwx13:


The center isn't THAT broad. Yes, it isn't a perfect consolidated circle, but it isn't very elongated either. We should see strengthening commence soon, if it hasn't started already.


It probably has started already, satellite appearance looks better than it did a few hours ago and the hurricane hunters are finding unsuspected readings of 55 mph.
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I still haven't forgotten about writing a poem when the season is over LOL
I got nuthin' though.
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Irene Vortex (8/21 15:28:50Z): MSLP: 1007mb; Inbound Flt. Lvl. Wind (Item F.): 29kts (~33.3mph); Max Flt. Wind (from Remarks): 53kts (~60.9mph) (View Data)
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Quoting Drakoen:


The 500mb heights are increasing to the north of Irene as she is just north of Hispaniola. Dangerous setup.
,that would leave no option other than directly nw into sefl??
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Wow! Looking at this model run, much farther North! I wouldn't be surprised if it missed Florida entirely.

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yes...please point out for us the humor in a tropical system striking this
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TS IRENE WV Loop
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting Grandpato4:
I had better take a break. All these images are going to give an old man like me a heart attack.




i save you with a drss on
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Quoting TropicalAnalystwx13:
Yikes



(Swallows hard)
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12z gfs 90 hrs out
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96 hrs...

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581. 7544
wow bad track getting stronger around andros island
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Quoting muddertracker:


If she does, will she get turned out before Fla?


Highly unlikely.
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Quoting LongIslandXpress38:


If Irene goes over Hati, game over. If it skirts north, Savannah better batten down their plantations!



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Quoting MiamiHurricanes09:
GFS basically depicting the worst case scenario. Little land interaction with ridge high pressure towards the north.
Irene looks like she is going to have jog north or south of her current trajectory to avoid those mts. of Hispanolia. IMO she is going to get torn apart with maybe a slight chance at reorganizing further north in the bahamas. Either way I don't see Irene being to terrible organized when she reaches the FL area. What you think?
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Yikes

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Quoting sarahjola:
excuse my weather ignorance, but does that mean that irene will be pushed towards the west? and if so, do you have any idea when that high pressure will build back in and how far it will build to the west? tia!


If the Bermuda High is strong enough then yes it will keep it in a WNW instead of NW direction. The timing is everything so it will be hard to tell if the approaching TROF would be stronger or weaker.
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Quoting TropicalAnalystwx13:
Irene should continue north of the forecast points as we progress through today...Puerto Rico, you may have a hurricane to contend with soon.


If she does, will she get turned out before Fla?
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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.