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 lucreto:
You guys got to be kidding me this system is no worse than Emily if it ever reaches hurricane strength it is likely due to error by the NHC rather than actual strengthening.


Let me see if I have this right. If the NHC makes an error then a storm can strengthen? But if they get it right then it can't strengthen? Who knew?
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Quoting Tazmanian:



plzs note that they do not do 55mph on storms any more so it will go too 60mph if they bump it
Oh, didn't know that. Man, things always changes...
Member Since: August 1, 2011 Posts: 28 Comments: 8075
Conditions deteriorating very quickly over Virgin Islands as might expect...

Current Weather Conditions:
Charlotte Amalie St. Thomas, Cyril E. King Airport, Virgin Islands
Aug 21 2011 / 3:53 PM EST / 1953Z

Wind: from the ENE (060 degrees) at 38 MPH (33 KT) gusting to 49 MPH (43 KT)
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Quoting TropicalAnalystwx13:
Levi, Drak, we need your expert analysis.
yes we do hopefully we can get a detailed analysis after the 5pm advisory
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Quoting FLdewey:
Arbitrary threat level update:

Those will potentially go up over the week.
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2367. Gorty
Quoting TropicalAnalystwx13:


lol, it puts me in the 50 kt. area.


I live in southern New England... Any chance I could see a hurricane (Irene)? A major will destroy New England from south to north!
Member Since: November 8, 2008 Posts: 12 Comments: 1058
advisory should be out real soon
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Levi, Drak, we need your expert analysis.
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2364. wpb
Quoting Abacosurf:
Starting to see a hint that we may see a little north westerly bend at the end of runs...

This must be due to the strength of the High building west.
what 18z model ?
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Quoting number4steel:
worst words i ever heard from a local weatherman, " i see an opening for fran"


I really don't want to hear that. I only moved to Raleigh-Durham in 1999 so wasn't here for that. Heard it was super scary
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It's not an eye, it's a feature! ; )
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I wouldn't trust the models right now if you are in Fl, Ga,SC,or Nc. The GFS is notorious for making the troughs stronger and the highs weaker.
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2359. Skyepony (Mod)
Irene

Loop
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2358. zparkie
Take the average for 4 hours and its still going west for a direct hit on puerto rico, after that we'll see how much goes over Hispanola
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Quoting NCHurricane2009:


LOL...if we were on the comittee to decide when to launch that music. or not..we might use it on every storm AND invest...LOL

(just kidding)....


Ah, but until then, we've got this...link.

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The center is actually a little ESE of ST Croix
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Next trouble maker is about to exsist Africa in about a day.
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2354. Dakster
Quoting WeatherNerdPR:

Do storms wobble when closing off their eyewalls? Irene seems to be wobbling WSW.


Storms always wobble...
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Quoting Tazmanian:




is that a eye froming on the rader?
yeap looks like we may have a hurricane later tonight
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Quoting TropicalAnalystwx13:


It is not moving westward.


The southern half of the center is on 17.5 N

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I see the last two Outflow Boundaries...Look how close it is in relationship to Puerto Rico...

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Quoting TropicalAnalystwx13:
Don't want to say this, but if it misses Hispaniola...

There is your next weather disaster for 2011.




is that a eye froming on the rader?
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
.
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Quoting TropicalAnalystwx13:
Don't want to say this, but if it misses Hispaniola...

There is your next weather disaster for 2011.

Yup. I completely agree. And it appears as thought it will either clip Hispaniola, or move north of it. And with the size of this system, whoever it hits would likely get a lot of storm surge.
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Quoting TropicalAnalystwx13:


It is not moving westward.

Do storms wobble when closing off their eyewalls? Irene seems to be wobbling WSW.
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Quoting USAFwxguy:


did they hint at it by coloring it yellow on their exclusive THREAT:CON map or whatever they call it?


no...put up the steering maps...simply said that it appears that Irene with the current steering will go just to the north of Hispanolia...if it does, the steering changes and so does the intensity of it...if it travels just to the north, it will be more influenced by the steering currents over the east coast as it wouldn't lose as much punch...no different than what everyone on here is saying by what THEY think the storm will do imo
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Quoting TropicalAnalystwx13:


lol, it puts me in the 50 kt. area.


It's put me in the 40 kt area in central GA lol. What a big system.
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Quoting MississippiWx:
Irene's core is certainly tightening up quickly...Radar is telling us that in precise terms.


It looks like its ready to moderately strengthen.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
worst words i ever heard from a local weatherman, " i see an opening for fran"
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Quoting TropicalAnalystwx13:
Don't want to say this, but if it misses Hispaniola...

There is your next weather disaster for 2011.
I knew you tried to put DOOM AND GLOOM on the blog.Lol.
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2334. zparkie
The models will jump all around, because the storm doesnt go in a straight line, spin a top on the ground and see what is does, it spins alittle to the right the models go to the right, it spins alittle to the left, the models go to the left, every four hours they take the average and determine track
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Quoting Tazmanian:



is that a eye wall froming on the rader?


correcto mi amigo taz pirate
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Quoting Abacosurf:
No.

Look at the southern half of the center. It is moving directly west. Maybe 275.

The center is elongated to the north.

Roughly 30 miles across.



It is not moving westward.
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Quoting AllStar17:


Yes. Because I think 85 knots = 90 mph and 90 knots = 100 mph.


80 Knots = 92.2 MPH
85 Knots = 97.9 MPH
90 Knots = 103.7 MPH

Close... :p

I have to work on my AP Homework. Be back in hour or two.

Member Since: August 1, 2011 Posts: 28 Comments: 8075
Quoting AllStar17:


Oh, I'm dying to hear your forecast.


Trolling cross the Atlantic until he finally gets the hook.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
guys remember that alot of the models were incorrect with TS Emily so do not rely on the models too much
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Quoting lucreto:
Looks worse than Emily geez you guys are ready to jump on anything if it has support from a group of models most know nothing about.
Don't spoil the mood on the blog with your negativity.
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Quoting BahaHurican:
Looks like Harvey wants to be reborn in the EPac....



The main invest over there isn't Harvey. He's still well over land.
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2324. FDNYR
http://weather.rap.ucar.edu/model/displayMod.php?va r=gfs_850_wnd&loop=1
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Quoting Gorty:


Holy crap, that is bringing 50kt winds close to my area!


lol, it puts me in the 50 kt. area.
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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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