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 MiamiHurricanes09:
Man, I can not fall asleep, lmao. Need to be awake in 3 and a half hours. Eeeeek.


you might do better not sleeping. Catch up tomorrow...
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6471. jonelu
Quoting TigerFanOrl:


Have you ever flown over South Florida? It's pretty much water with a little land mixed in and flat as can be without being below sea level. Not a whole lot to do much disruption. I believe Katrina did well over South Florida.
So did Wilma
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Reports of building windows blown out near the airport.
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Quoting 1million:


Tampa has the shield... :-)



Sort of like the Cubs do in baseball against the big one?
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Quoting weatherman12345:
lol miami.. still up
Man, I can not fall asleep, lmao. Need to be awake in 3 and a half hours. Eeeeek.
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Quoting swflurker:
really, Levi? Thanks Me and NEA live is SW FL.


I'm in N. Ft. Myers...payin' attention!
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6466. Levi32
The 0z Euro is slightly farther north than the 12z so far, and still a scary track through the Bahamas that could allow strengthening, no matter where the final landfall is.
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Quoting 1million:


Tampa has the shield... :-)



Yes we do and it works well ... :-p
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Can't get to sleep, Miami?
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6463. 7544
hmmmm looks like eruo is goona join the pack might be with the cmc and gfdl this run
Member Since: May 6, 2007 Posts: 0 Comments: 6812
Quoting scottsvb:
Irene is a easy storm to forecast..hardest part is the near term of her moving more WNW with NW wobbles staying east of the initial model runs.

Nothing has changed in the future track as the models have a short term westward bias due to weak initialization of the system and too much ridging to the north of Irene. She will bend more W but still this is a Bahamas-Carolinas system. Chance of this making a "Landfall" in florida south of Daytona is around 10% right now


Concur
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Quoting sunlinepr:
The "Cordillera Central" Central PR mountains, although not as high as DR's, have affected the visible COC in the Radar...


Looks like the COC is over El Yunque right now...about to head into San Juan.
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Member Since: July 15, 2006 Posts: 17 Comments: 10249
72 hours:


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Quoting Levi32:


To be blunt, I think the 0z CMC is trash. The rest are ok, but some may be jumping it west too much right off the bat. We'll see what the long-term movement is tomorrow, as these storms like to dance around the islands and wobble all over the place due to frictional effects.
Very well said ...

Puerto Rico is not mountainous enough to tear her apart, but it will change her course in ways that the models cannot predict.
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Quoting 1million:


That would be interesting...


Tampa has the shield... :-)

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Quoting hurricanejunky:


Well if you refer back to the 1935 Labor Day Hurricane it went from TS to Cat 5 very rapidly over the warm waters of the western Bahamas and Florida straits. Quite a hotbed for RI


Um, I agrees with you. Went from Tropical Storm to almost 200 MPH Category 5 in only a day or two. Officially, it's 185 MPH storm... but 200 mph winds may have occurred during this storm. Nasty one...

Member Since: August 1, 2011 Posts: 28 Comments: 8009
Irene appears to be headed to the North of the cone or more like a Carolina storm.
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6453. NCSCguy
Well looks like I need to go to the store then.
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Member Since: July 15, 2006 Posts: 17 Comments: 10249
Quoting hurricanejunky:


Fay was one of the rare notable instances where a TC strengthened after landfall.


Have you ever flown over South Florida? It's pretty much water with a little land mixed in and flat as can be without being below sea level. Not a whole lot to do much disruption. I believe Katrina did well over South Florida.
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The "Cordillera Central" Central PR mountains, although not as high as DR's, have affected the visible COC in the Radar...

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Quoting jonelu:
That is very scary....I really hope that does not happen.


I bet it doesn't ... seems impossible... lol
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really, Levi? Thanks Me and NEA live is SW FL.
Quoting Levi32:
0z GFDL:

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6447. Levi32
Quoting NCSCguy:
Levi, what is your best guess as to where Irene will make landfall?


My track from this morning still stands, and I have her going into South Carolina. However, I will continue to stress that very small shifts in a track like this can cause the landfall to jump into different states, so everyone from Florida to North Carolina is at risk for a landfall here.
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Quoting bayoubrotha:



Well, Irene won't have to wobble much to the NW to exit PR since her current position is only 15 miles SSE of San Juan and she is moving 15 mph.


Should be out of there by the 5am advisory.
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Quoting Levi32:


It's worth keeping in mind that the HWRF more often than not is overly aggressive on intensity. We will know more about Irene's peak intensity after she gets away from Puerto Rico and Hispaniola.



However its is not out of the question with minimal land interaction and bath water all the way to the coast that this thing ramps up very fast. Hugo did once it hit the gulf stream
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6444. NCSCguy
Levi, what is your best guess as to where Irene will make landfall?
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Quoting Levi32:


Correct, but we'll have to see. Often NW wobbles around an island mass like this are short-lived. Obviously any kind of northward jumps right now are bad news for those hoping Irene will weaken over Hispaniola.



Well, Irene won't have to wobble much to the NW to exit PR since her current position is only 15 miles SSE of San Juan and she is moving 15 mph.
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If Weather Channel continues with Category 1/2 landfall and Irene MAYBE goes under RI into Category 4, things will get ugly fast as people will not have time to prepares for this strong of storm or to evacuate from Florida to Georgia. SC/NC will have little more time.
Member Since: August 1, 2011 Posts: 28 Comments: 8009
Quoting jonelu:
That is very scary....I really hope that does not happen.


What does it do?
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24 hours out on the Euro...Takes Irene just north and east of Hispaniola, which is probably more realistic.

Member Since: July 15, 2006 Posts: 17 Comments: 10249
Quoting sunlinepr:


Thanks, looks like it's not a big strike, for the moment.... Just called my sister in Ponce (SW of the eye) and they are still waiting for the rain and the wind... Don't know if any here in Ponce...



Sure do hope that's all you guys get!!
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Quoting MississippiWx:
GFDL still takes it over the extreme Gulf. It also has it strengthening rapidly once over land in South Florida, which is not realistic.



Fay was one of the rare notable instances where a TC strengthened after landfall.
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New Euro so far
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6436. Levi32
Quoting Bluestorm5:
well... guess we'll find out soon enough. At least Weather Channel is telling people in Florida to go over their evacuation plans, get ready to prepares for this storm, and get more supplies soon enough.


At least they're doing something right at TWC.
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6435. 7544
wow wow cat 4
Member Since: May 6, 2007 Posts: 0 Comments: 6812
6434. jonelu
Quoting Levi32:
0z GFDL:

That is very scary....I really hope that does not happen.
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Quoting benirica:
Let's see what happens... odds are the will name it a Hurricane AFTER Puerto Rico, this has been the scenario before. Since at this point 70 or 75mph is pretty much the same, I wouldn't be surprised if for insurance purposes they hold it off and upgrade it once it's someone elses money.
I say this because it has happened before, Jeanne I believe, the storm enters like this one and once it is out on the Mona Passage it is upgraded.
End result, farmers who loose crops can't ask for money from insurance because it wasn't a hurricane... only a TS.


Most insurance covers named storms. TS or hurricane, as long as it's got a name.
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6432. 7544
u guys are v fast lol thanks
Member Since: May 6, 2007 Posts: 0 Comments: 6812
6431. Seawall
Quoting thedawnawakening3:


You're reading it wrong, that is a model depiction of Irene as she nears SC for landfall over open waters, over PR right now she is at 70mph.


Thanks for the clarification.
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GFDL shows peak surface winds of around 140mph.
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Quoting alvarig1263:


Move that over a little bit more to the west and we'd have a Cat. 4 hitting South Florida with in 100 hours. Incredible how warm those waters are and how quick irene could really intensify. Watch out FL! (including myself)


Well if you refer back to the 1935 Labor Day Hurricane it went from TS to Cat 5 very rapidly over the warm waters of the western Bahamas and Florida straits. Quite a hotbed for RI
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Quoting scottsvb:


It's slowing shifting east each run... probably be in the bahamas and stay east of 79W by the 12z run.


Pretty good consensus now with GFS,CMC and now GFDL.
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Quoting Levi32:
0z GFDL:



That would be interesting...
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GFDL still takes it over the extreme Gulf. It also has it strengthening rapidly once over land in South Florida, which is not realistic.

Member Since: July 15, 2006 Posts: 17 Comments: 10249
6425. Seawall
Nowcast as of 10:58 PM AST on August 21, 2011
Rain bands associated with Tropical Storm Irene have been affecting the U.S. Virgin Islands...Culebra...Vieques and eastern Puerto Rico during the past couple of hours. Residents should expect additional heavy downpours and sustained winds in the 50 to 70 mph range with gusts to 80 mph across these areas. Additional rain bands with strong winds will spread into Mainland Puerto Rico during the next several hours.
Flash Flood Watch in effect through Monday afternoon...
Hurricane Warning in effect...
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Quoting Levi32:


Correct, but we'll have to see. Often NW wobbles around an island mass like this are short-lived. Obviously any kind of northward jumps right now are bad news for those hoping Irene will weaken over Hispaniola.
well... guess we'll find out soon enough. At least Weather Channel is telling people in Florida to go over their evacuation plans, get ready to prepares for this storm, and get more supplies soon enough.
Member Since: August 1, 2011 Posts: 28 Comments: 8009
Right when the models were starting to be consistent a day or 2 ago, now they cant seem to make up their mind, well, resume the waiting game.
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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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