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 interstatelover7165:
Considering that the HH are in St Croix, it certainly won't take them long to get to Irene.


Just fly straight upwards...

Helicopter would be more convenient. Though, actually, a helicopter in a TS probably isn't the best idea.
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Quoting AllStar17:




LOL. My bad......I meant Irene. I was just reading Harvey's public advisory. At least there was no profanity in my typo.

Windsh*t! LOL
Still remember
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2621. hotrods
Hmmm! NHC track not good for ECFL north and east quad could make it bad here even if it is a storm. Florida flat lands, ala-Fay.
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2620. Relix
People in Puerto Rico know pretty much this is the real deal by now. People here have experience with hurricanes... real hurricanes... so this won't be much of an issue except for flooding, and even that I believe won't be as bad because the strongest rains are to the north far in the sea.
Member Since: August 3, 2006 Posts: 0 Comments: 2722
Well looks like I am still very much in the cone of doom at least at the moment...hearing soft violin music playing in the background lol.
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Quoting robj144:


Harvey's coming back around? :)


Quoting WeatherNerdPR:

Harvey?!


LOL. My bad......I meant Irene. I was just reading Harvey's public advisory. At least there was no profanity in my typo.
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Quoting SavannahStorm:
Gusting to 60 on the St. Croix northern coast. Pressure still dropping.


That is one heck of a drop in air pressure!
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2616. Gorty
Could the center possibly relocate just to the east of PR? Look at that convection, almost pure curricular.
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I think Irene will surprise a few and move south of PR and just skim the coast of DR/Haiti to the south. Next few hours should be interesting. JMO.
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2614. WxLogic
18Z @84HR 500MB:

Interesting... cut-off low, such a solution could weaken the steering for Irene.





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Considering that the HH are in St Croix, it certainly won't take them long to get to Irene.
Member Since: August 18, 2011 Posts: 0 Comments: 994
Tropical Storm Warnings in Mexico, Harvey expected to become a tropical storm again.

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2610. Torgen
Quoting thelmores:
Sat pic older than radar, but I believe caught the COC.......

Irene gonna be a trouble maker! Feel Bad for Hispaniola..... lives may be lost......






ya know, watching them get destroyed over and over, *every* year without end, and I can't blame them for grabbing a 2x4 and trying to paddle to the US. I'd be doing the same thing.
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2609. scott39
Quoting Levi32:


Well the cone will be centered around the track no matter what, but in my opinion, a track up the peninsula of Florida is just about as far west as we can hope for now.
I understand
Member Since: June 13, 2009 Posts: 0 Comments: 6774
2608. HCW
Watches and Warnings

Member Since: August 10, 2002 Posts: 0 Comments: 1408
Quoting thelmores:
Sat pic older than radar, but I believe caught the COC.......

Irene gonna be a trouble maker! Feel Bad for Hispaniola..... lives may be lost......






Good to see ya thel. Ready for the "Other Season"?
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Quoting AllStar17:
If Harvey continues on a heading between about 287 and 290...it will just graze Hispaniola.

Harvey?!
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Quoting HurricaneDean07:
NHC giving it a 3% of cat. 2 before DR, and 10 % before landfall, though they will have to change that equation with the news that its likely going to have more time to strengthen before the Carolinas, not florida


I think that those percentages are reasonable if Irene were to follow the current NHC track. IMO, the track will shift quite a bit east, so Irene should have quite a bit more time to strengthen.
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2603. Seastep
Quoting WeatherNerdPR:
...CENTER OF IRENE NEAR ST. CROIX...
5:00 PM AST Sun Aug 21
Location: 17.7°N 64.4°W
Max sustained: 50 mph
Moving: WNW at 17 mph
Min pressure: 999 mb


Due E of St. Croix and about to landfall.
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2602. WxLogic
Quoting USAFwxguy:


which leaves that second trough as the worrisome feature


If it's not strong enough then could be interesting for some.
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2601. robj144
Quoting AllStar17:
If Harvey continues on a heading between about 287 and 290...it will just graze Hispaniola.


Harvey's coming back around? :)
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Feel bad for Puerto Rico, this is more then a 50 mph storm and I hope they are not just expecting another Emily.
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2599. Gorty
The NHC is being very conservative.
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Gusting to 60 on the St. Croix northern coast. Pressure still dropping.

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NHC giving it a 3% of cat. 2 before DR, and 10 % before landfall, though they will have to change that equation with the news that its likely going to have more time to strengthen before the Carolinas, not florida
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Quoting P451:


Texas? No.

Interesting that he has a chance at regeneration.

A few models, particularly the GFDL had it emerging in the BOC.



This to me it an example of "storms" having their own mind. Anytime they sense a chance to get back over water they do so. It was why I kept saying that Harvey would emerge over the BOC. Now the chance to become a hurricane is gone because he stayed too far to the south but it might be interesting if he pulls a trick.

IMAGINE IF HE TURNS NORTH LOL

The entire blog would go crazy.
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If Harvey continues on a heading between about 287 and 290...it will just graze Hispaniola.
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Quoting TropicalAnalystwx13:
Cone still needs to be shifted east..


I agree.
Member Since: September 2, 2006 Posts: 110 Comments: 6877
2593. Levi32
Quoting scott39:
what about the margin of error. Wouldnt that put the Cone over the E GOM?


Well the cone will be centered around the track no matter what, but in my opinion, a track up the peninsula of Florida is just about as far west as we can hope for now.
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Quoting tropicfreak:


I can't believe they still have it at a 50 mph storm.
I think they will hold off till recon goes in again, but in the past few frames, it looks like it's getting stronger
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2591. Grothar
GFS ensemble model

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Sat pic older than radar, but I believe caught the COC.......

Irene gonna be a trouble maker! Feel Bad for Hispaniola..... lives may be lost......




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Quoting tropicfreak:


I can't believe they still have it at a 50 mph storm.


Recon will be in before too long, if it's stronger they'll up it then.
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2588. HCW
Member Since: August 10, 2002 Posts: 0 Comments: 1408
Quoting Levi32:
The current motion should take Irene over a portion of Puerto Rico and then the northern part of the Dominican Republic.


Is that the expected more northerly track you were discussing in your blog this morning?....or is that a bit more southerly that what you were thinking this morning?
Member Since: September 15, 2009 Posts: 473 Comments: 3668
Quoting tropicfreak:


I can't believe they still have it at a 50 mph storm.


The Hurricane Hunters are flying into the system around 8PM, we'll see what they find.
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Anyone seen Miami Hurricane today?
Member Since: December 3, 2010 Posts: 0 Comments: 54
Quoting JrWeathermanFL:
I think Irene will be like a mix of Hugo and David.
I live in Savannah...that's not good
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NHC track pretty reasonable 60 Hours out, but dont agree past that time frame, also still not very strong with this system for it having less impact then previous, it has it from a hurricane to moderate TS after skirting the coast of DR, which doesnt make much sense, since thats the same intensity in the last few advisories when it was going directly over Hispanoila
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Quoting P451:


lol... can't be!


:o




I can't believe they still have it at a 50 mph storm.
Member Since: September 2, 2006 Posts: 110 Comments: 6877
2580. MZT
Quoting USAFwxguy:


the cone is an automatic is it not? based on historical error average or something like that
Yes the cone is based on a 2/3 confidence level. Irene could still move outside the cone and the NHC would shrug and say "we try to get it two out of three times"
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Quoting shawn26:
not much of a shift considering all of the model shift


Just wait till the shift hits the fan!
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Quoting TropicalAnalystwx13:
Cone still needs to be shifted east..


You must have downloaded a copy of the REED model.
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I agree that Irene is moving very close to W at the moment based on radar, the closing of the eye tricks the eye into seeing a more northly component.
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Quoting RickWPB:
Well the cone shifted a bit east. Now instead of aiming at Miami, it's centered on West Palm Beach!


or pompano/delray.....
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2573. scott39
Quoting Levi32:
NHC staying left of the model consensus. The track they show into east Florida is a very possible one, though I disagree with the cone over the eastern Gulf of Mexico.
what about the margin of error. Wouldnt that put the Cone over the E GOM?
Member Since: June 13, 2009 Posts: 0 Comments: 6774

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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.