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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should see 60 Mph later today, and 65 mph tonight, all depends though, She needs to pull it together for that to happen though, "Good luck to ya PR" hope you guys bode well through this strong TS/Cat 1
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. TaylorSelseth- please no race baiting on the blog! our politicians do it enough. and for a bunch of racist people we sure sent those (not white people) a ton of money, and doctors,and love. i hate when people race bait!
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BEHOLD
Irene's Center
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Quoting Patrap:


Always pay attention to the width of the cone at the end.

..if your n there downstream, keep up with IRENE.


that rhymes...in a drunken, drug flavored, rock n roll sorta way
Member Since: August 13, 2007 Posts: 0 Comments: 10492






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Quoting lennit:
ok according to recon she is still not vertically stacked 850 and surface are 5 miles apart and only 1007 so she is truckin along at 270 true at about 20 mph until she gets stacked deep layer steering will not affect her nor will she intensify she has to slow down


I think that is why she is moving more north of the forcasted points. Models were assuming it would have been stacked by now.
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Quoting AllStar17:
Looking at visible loops, I still see Irene heading north of due west.
Link


Agreed.
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Quoting sullivanweather:


2005 Ophelia - never got over cat1 while meandering over the Gulf Stream
1999 Dennis - went from cat2 to tropical storm while stalled over the Gulf Stream
1999 Floyd - Turned and slowed over the Gulf Stream and weakened from cat 4 to cat 2
1995 Felix - Performed a very slow right turn over the Gulf Stream, only maintained strength.

The Gulf Stream hardly ever intensifies storms because of proximity to land and the typical presence of a frontal boundary in the region of the East Coast providing shearing winds. The Gulf Stream historically is only able to maintain the strength of systems encountering this more hostile environment.
Depends on the environment,we had Bonnie in 1998 intensify back to a hurricane while right on the coast of N.E. North Carolina,That was quite a surprise! Dennis upwelled the waters off the coast ,so when Floyd slowed, it did not have the heat content to feed off of.
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Irene should refire some convection over the center shortly.
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862. Skyepony (Mod)
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861. MZT
Quoting tryingtolearn:
as a very new person to this and i do mean new this is only my second post ever on this site, i am trying to figure out what is going on. And i guess at a time like this is not the time.
Discount most of what you read in the comments. You can learn bits of analysis from people but after six years of watching this blog, my conclusion is the NHC knows their game and get their forecasts right.
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Looking at visible loops, I still see Irene heading north of due west.
Link
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Most of you have been tracking or watching hurricanes for quite some time. As scary as some of the models can be sometimes, all of you realize how they change from day to day, hour to hour. There are still alot of things to take into consideration right now. If anyone is locking onto 1 or 2 models this far out, they are crazy.
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Quoting Klolly23:
If Irene remains weak due to interaction with landmasses, then what are the chances she slips under south FLA and runs up along the west coast of FLA...


Always pay attention to the width of the cone at the end.

..if your n there downstream, keep up with IRENE.
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the longer she takes to stack the more west she goes.. models are assuming she is already stacked and pressues are lower the what the are..
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Quoting HurricaneDean07:
Hurricane probably in about 24 hours give or take some, but Irene needs to blow up more convection on the south side, she's very lopsided


Agreed, South side of the storm is looking very disorganized but there is clearly a circulation, I bet tomorrow morning we'll see something completely different.
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Quoting barotropic:


Nope...not this time for Fla IMO...cone shifting this eve....eastward and Bahamas in big trouble, we will see. obviously to soon to bank on anything.
It's Irene people and she has returned to SFLA. Let's welcome her back with open arms! LMAO
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Quoting NCHurricane2009:


Using that same radar image...I see the broad center moving into the SE corner of Puerto Rico....


That is not the center. The center is still East and South of P.R.
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Quick question. If there is a hurricane or strong tropical storm approaching St. Croix. Where do the HH planes take off and land from?
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Keep in mind the 6z and 18z model runs aren't always the more accurate runs - 0z and 12z runs normally have more information in them and give a better idea of where a system is going.
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829. cchsweatherman

Tropical Storm Irene appears to be resuming a more westward course as indicated by the past few Hurricane Hunter fixes.


Exactly! And just might stay on this course for a while...
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847. wpb
Quoting barotropic:
HwrF 12z shifting north early on like GFS....shows Irene moving over puerto rico clipping NE tip of DR and over water on north coast.
keep those updates on the blog thanks
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Quoting 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.
Not liking the Floyd / Isabel references there... Isabel had me spitless for a week before the turn, and Floyd turned over the Bahamas... still have the scars to prove it... lol

Quoting osuwxguynew:



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.
Actually the info on the 3-day track is pretty excellent. I think all those Caribbean pple out buying stuff and putting up shutters absolutely expect it to pan out... The Bahamas / Cuba will know what to expect by tomorrow morning... 48 hours, basically.

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Hurricane probably in about 24 hours give or take some, but Irene needs to blow up more convection on the south side, she's very lopsided
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NHC- upgraded to Hurricane Warning for Puerto Rico. This system will pass to close for comfort and residents should be prepared for the worst. The only good thing right now is the speed of the circulation center which should keep rainfall rates lower to 8-10 inches vs. 20 as can happen with slow moving systems. PR could take the brunt of the system as it crosses near by with strongest winds and rain to its north impacting the San Juan metro area. Weather will deteriorate significantly over next 4 hrs.

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If Irene remains weak due to interaction with landmasses, then what are the chances she slips under south FLA and runs up along the west coast of FLA...
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Quoting masonsnana:
Go wake him up Shawn :)
he will be here soon just finishing up with the flush model

lol
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Quoting wxhatt:
Look at this, gaining lattitude all the time. On this trajectory, it may even get on the north side of PR.

This is what the models are seeing. I expect a shift even farther to the east...




Using that same radar image...I see the broad center moving into the SE corner of Puerto Rico....
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Levi is going Cane Wrestling with CycloneOZ, ..?

Huh,..?
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Very tempting
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Quoting atmoaggie:
As of 12 UTC, the historical analogs, based on track thus far and current position, are the following.



And, given the synoptic setup, the 2 western tracks of yesteryear shown above can be discounted entirely.


I am thinking it will be closest to the path of Tropical Storm Chris (Link) -- however the intensity when it approaches the mainland is anybody's guess.
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HwrF 12z shifting north early on like GFS....shows Irene moving over puerto rico clipping NE tip of DR and over water on north coast.
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Quoting sullivanweather:


2005 Ophelia - never got over cat1 while meandering over the Gulf Stream
1999 Dennis - went from cat2 to tropical storm while stalled over the Gulf Stream
1999 Floyd - Turned and slowed over the Gulf Stream and weakened from cat 4 to cat 2
1995 Felix - Performed a very slow right turn over the Gulf Stream, only maintained strength.

The Gulf Stream hardly ever intensifies storms because of proximity to land and the typical presence of a frontal boundary in the region of the East Coast providing shearing winds. The Gulf Stream historically is only able to maintain the strength of systems encountering this more hostile environment.


You have a point here....only rarely does it help to strengthen a storm....like last year's Earl...which went to cat. 4 off the SE US because it wasn't in an unfavorable atmosphere like these others you cited...
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check out my blog for latest tropical information

Link

and always follow NHC/TPC for all of your official forecasts and life threating information
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as a very new person to this and i do mean new this is only my second post ever on this site, i am trying to figure out what is going on. And i guess at a time like this is not the time.I live about 1 hour from the gom in louisiana, i truly dont like what i am seeing, not for myself but for florida. I have a soon that lives there and i think i will be calling him today to see if he is up with what is going on.
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Just check up on what recon found earlier found a large swath of 50 to 55 mph winds at the surface that were uncontaminated, and some flight level winds of 65 mph... PR, watch out she's coming for you...
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Quoting shawn26:
We need Levi
Go wake him up Shawn :)
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Tropical Storm Irene appears to be resuming a more westward course as indicated by the past few Hurricane Hunter fixes.
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ok according to recon she is still not vertically stacked 850 and surface are 5 miles apart and only 1007 so she is truckin along at 270 true at about 20 mph until she gets stacked deep layer steering will not affect her nor will she intensify she has to slow down
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Oh man only an hour until the 2pm advisory is posted 75 times. Can't wait!
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Quoting shawn26:
We need Levi


I think he was checkin' out a flight attendant on the plane last night...he may not be available for a while...
Member Since: August 13, 2007 Posts: 0 Comments: 10492
Quoting TropicalAnalystwx13:


I don't see any outflow boundaries, just a lot of cirrus.



The western part of the system is developing an outflow boundary.
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Good Morning. Lots of the folks on the Blog certainly follow the models and NHC bases their track on the model guidance as well. While we can certainly speculate as to where the models will shift to based upon emerging conditions, best thing to do IMHO (certainly for the general public) is to focus on the NHC 3-Day track which is the best educated guess out there. Also, since this is such a large storm, it will have far reaching impacts so do not focus on the center line but prepare accordingly if you are in the 3-day cone just in case.
Member Since: August 8, 2006 Posts: 0 Comments: 9402

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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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