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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All this W, WSW or WNW talk has me seriously considering whether or not I should keep hitting F5.
Member Since: Posts: Comments:
Quoting stormwatcherCI:
I see that too but others are saying wnw so IDK.




its west maybe possibly just north of west however its current heading imo is west look at patrap latest loop
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Quoting TropicalAnalystwx13:
I must say, Irene has the satellite appearance of at least a 70 mph storm. Look at the banding features, the outflow, the bulk of convection to the N/NE of the center, just wow...



I agree with that. I think it's nearing hurricane intensity so no 50 mph like nhc says.
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3369. Levi32
Quoting NCHurricane2009:


Would you say it has been moving WNW or west over last hours...I keep getting mixed messages about current motion when studying radar and sat loops...I really can't tell right now....


A little bit north of west, I would say, but not due west.
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Plane found the circulation... over the airport. Went from northwest to southeast in winds while flying over it. lol
Member Since: August 1, 2011 Posts: 28 Comments: 8030
""

I think the coc is now in the dry air trying to close off an eye.


""

98l looked good... Irene looks great on here though

""

850 mb

""

700 mb

""

500 mb

This is stacked perfectly... sorry for my absence I was banned
Member Since: June 17, 2011 Posts: 11 Comments: 6539
Sorry folks, but she is going to skirt the south side of PR. Vis sat loop clearly shows what is going on.
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I agree also...it's not moving wnw but more west and possibly a little south of west which is not unusual considering the steering flow.

Quoting chrisdscane:




look at the satelite and radar its moving west ok, mayne even a sw job if u look closely and analyze it u'll see
-
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Quoting chrisdscane:




look at the satelite and radar its moving west ok, mayne even a sw job if u look closely and analyze it u'll see
-


If you look at long animation satellite, it Moved WNW overnight last night, but the past 4-6 hours it has moved much closer to W, maybe slightly north of due W
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Quoting P451:
In the latest radar frame I think I saw an easterly jog.

Yep, I did, it's heading East. To NOLA. It's just going to take a really long time to get there.

East? back to the lesser Antillies?
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Quoting hurricanehunter27:
Im gona say its a hurricane right now. If not, really close.
I agree.
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3359. MahFL
That radio station is pretty cool.
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Quoting MississippiWx:
Recon couldn't have been in a better place to start this mission.


Or a better time... while the calm center is over the island.
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3357. breald
Quoting Grandpato4:
I just met someone that follows this blog while out for dinner on the beach. Becky, if you are reading it was nice meeting you.

I was mentioning that I had seen models starting to point Irene towards the Carolinas and she asked where I get my information and I said WU. She said, No way I am on that website every day but I don't post much.


It's a small world. :)
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Quoting benirica:
If it is going to intensify I sure hope it makes landfall as a hurricane.
It would be sad to have a repeat of TS Jeanne back in 2004... came in as a 70mph storm and devastated crops. Unfortunately, since it was a tropical storm insurance for the farmer's losses did not cover.

$197 million in damage was no joke...
Member Since: July 7, 2010 Posts: 0 Comments: 5690
Im gona say its a hurricane right now. If not, really close.
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Quoting Stormchaser2007:


GRLevel2 Analyst with a bunch of placefiles


You had to buy them didn't you?
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3352. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128667
Plane going to NE toward the strongest part of Irene. I think they'll find ~63knots flight level, ~55 knots surface. What ya'll think?
Member Since: August 1, 2011 Posts: 28 Comments: 8030
3350. Grothar
Quoting TropicalAnalystwx13:
I must say, Irene has the satellite appearance of at least a 70 mph storm. Look at the banding features, the outflow, the bulk of convection to the N/NE of the center, just wow...

Quoting TropicalAnalystwx13:
I must say, Irene has the satellite appearance of at least a 70 mph storm. Look at the banding features, the outflow, the bulk of convection to the N/NE of the center, just wow...



Yep, beginning to take on that comma shape like I mentioned about an hour ago. Interesting to see what it does tonight. I hope all our friends in PR and the other islands stay safe.
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Quoting Levi32:
Recon taking off in the center of the storm lol. 995.4mb pressure.
Wonder how many times that has been done....LOL
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Quoting TropicalAnalystwx13:
I must say, Irene has the satellite appearance of at least a 70 mph storm. Look at the banding features, the outflow, the bulk of convection to the N/NE of the center, just wow...



She HAS to be stronger in the next advisory...just has to be....
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Quoting c150flyer:


What program is that that you are using??


GRLevel2 Analyst with a bunch of placefiles
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Quoting OracleDeAtlantis:
She looks to me, to be going a little southwest now.
I see that too but others are saying wnw so IDK.
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its definetly looking like shes going
west not wnw
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i have 997 on my personal weather station
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3343. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128667
Quoting NCHurricane2009:


Would you say it has been moving WNW or west over last hours...I keep getting mixed messages about current motion when studying radar and sat loops...I really can't tell right now....




look at the satelite and radar its moving west ok, mayne even a sw job if u look closely and analyze it u'll see
-
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Quoting Clearwater1:
Many here will disagree with you, but I've been thinking at least due west. We shall see.
It appears it's shifting a little wsw but I think it's an illusion of shawdows created by high cloud tops and a few other factors. See the visible loop for that. To me it looks like the center is going to pass right over the south portion of PR. t
This might hinder developement some.
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If it is going to intensify I sure hope it makes landfall as a hurricane.
It would be sad to have a repeat of TS Jeanne back in 2004... came in as a 70mph storm and devastated crops. Unfortunately, since it was a tropical storm insurance for the farmer's losses did not cover.
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When using pressure, a Category 1 hurricane has pressures lower than 994 mb...Recon just found 995 mb. This leads me to believe that the system is around 70 mph at this time, and I believe that recon will find some interesting readings...

The pressure thing does apply to Irene since she is NOT of monsoonal nature like Alex of last season was.
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Quoting stormwatcherCI:
Actually I am hoping it heads straight to FIU where your dorm is. Back off.


I guess if some here had experienced what we did with Ivan in 2004 , they wouldn't be so quick to call us wishcasters, we just call it like we see, whether right or wrong, we're entitled to our opinions, don't let such persons get to you , I've learned to basically just pass them by, anyway when they experience a major hurricane that pounds them for 36 hours non stop and its consequences maybe they'll grow up a bit, just saying...
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Lowest pressure so far is 995.4
Member Since: August 1, 2011 Posts: 28 Comments: 8030
Quoting Stormchaser2007:


Hopefully this clears it up for the folks who thinks its heading WSW...

It's clear the coc is over st Crx., So, if the coc is over PR in a few hours or so, the def. wnw. If it's south of PR, well then heading west. But def came up to St. Cr from St. Kits. That's def wnw
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Quoting stormwatcherCI:


If these are the current steering layers for the strength that Irene is can someone please tell me how she can go WNW when it looks clearly West or even a little WSW. Also, is the line with the arrows on it a ridge or if not what is it ?
She looks to me, to be going a little southwest now.
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69mph winds in squalls,reported in Charlotte Amalie, Saint Thomas...
Member Since: May 31, 2011 Posts: 0 Comments: 917
I must say, Irene has the satellite appearance of at least a 70 mph storm. Look at the banding features, the outflow, the bulk of convection to the N/NE of the center, just wow...

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Quoting Stormchaser2007:
Down to 996



What program is that that you are using??
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3326. Levi32
Recon taking off in the center of the storm lol. 995.4mb pressure.
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they this found 995mb

995.4 mb
(~ 29.39 inHg)
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Quoting Levi32:


Yes, because it puts it on a line to Puerto Rico for its first real landfall.


Would you say it has been moving WNW or west over last hours...I keep getting mixed messages about current motion when studying radar and sat loops...I really can't tell right now....
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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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