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 caneswatch:
If Irene misses Hispaniola, it's a whole new ballgame.


Will be watching the PR radar very closely tonight to see if it does just that. Sounds like whether it goes over or N of Hispanolia will decide a lot about the path it takes, and even more so about the future intensity.
Member Since: Posts: Comments:
Hi all. Thanks for all the great information. I was wondering if East Central Florida is off the hook for Irene? I have to take a trip later this week and I need to know whether I should change my plans.
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first rain bands arrive @ ponce pr.
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting AllStar17:


SE.
Thanks.
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To me PR will avoid the worst (northern-northeast)part of the storm, even if center passes directly over it. God is great!
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Quoting caneswatch:
If Irene misses Hispaniola, it's a whole new ballgame.
A violent ball game at that.
Quoting Bluestorm5:
Man, the name of Irene just sound like one of those "major hurricane" names.
In my pre-name season predictions I had Irene as a major hurricane.It could happen.
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2267. FDNYR
Link
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here i another point we need to pay close attention to the trofs that are coming down and see how strong they are they will probably determine if irene makes a direct hit on south florida or does a Hurricane Floyd type track offshore the florida east coast
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2265. Gorty
Quoting Bluestorm5:
I'm going with 55 mph to 65 mph range for 5 pm.


Same with me.
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Quoting stormwatcherCI:
It's bogus.


That is very irresponsible and should be noted by blog administrators.
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2263. P451
We're in business. WNW it continues - aiming right for eastern PR. Strengthening. Tightening up. ETc...it's all right here to be seen.




Member Since: December 16, 2007 Posts: 7 Comments: 10202
Quoting FLWeatherFreak91:
I don't think I've ever seen the NHC issue an advisory of 55mph...


They can only do it on intermediate advisories.
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Quoting Grothar:
The modesl on the 12 Z moved east, but on the 18Z moved slightly back west









Interesting.
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I wouldn't be suprised if its still at 50 mph....at 5 PM that is
Member Since: September 15, 2009 Posts: 525 Comments: 3701
i see our raliegh nc radar is out again( happens about once a week)
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Quoting Grothar:
The modesl on the 12 Z moved east, but on the 18Z moved slightly back west







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.
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Still not entirely convinced that this is an eye, but it's certainly interesting.
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Why does TWC still have it going through Florida? Did something change?
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Quoting Bluestorm5:
I'm going with 55 mph to 65 mph range for 5 pm.
I don't think I've ever seen the NHC issue an advisory of 55mph...
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They may keep it at 50 mph since recon isn't out there...But, I will say 60 mph.
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Quoting NICycloneChaser:


Would seem that way. Certainly no difficulties with water, it's all 29 degrees and above. The ULAC should stop shear from becoming a problem. Environment is fairly moist around that area too.

Is that our trough dipping over KY right now?


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Quoting Grothar:
The modesl on the 12 Z moved east, but on the 18Z moved slightly back west







i still think its going to come dangerously close to SE florida
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Quoting stormwatcherCI:
Can someone tell me where this buoy is in relation to the COC of Irene if the winds are SW.

Station 42060
NDBC
Location: 16.333N 63.5W
Conditions as of:
Sun, 21 Aug 2011 18:50:00 UTC
Winds: SW (230°) at 7.8 kt gusting to 11.7 kt
Significant Wave Height: 6.6 ft
Dominant Wave Period: 10 sec
Atmospheric Pressure: 29.78 in and falling
Air Temperature: 78.1 F
Dew Point: 73.8 F
Water Temperature: 84.2 F


The buoy is to the SE.
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Quoting Grandpato4:


I cannot find any information on this model. Is it new or experimental? Can you post a link?
It's bogus.
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2249. KEEPEROFTHEGATE (Mod)
09L/TS/I/C0
MARK
17.85N/64.65W
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Quoting TropicalAnalystwx13:
Always liked this compared to all the other ones..

I liked 2004-05 and 06-07 ones the best.Never did like 2008.Didn't sound doom enough like the others.In other words it sounded soft and didn't catch my attention like that.
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If Irene misses Hispaniola, it's a whole new ballgame.
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Buoy in St. Croix is reporting 22 kts. (28 mph) and rapidly falling pressure.
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I'm going with 55 mph to 65 mph range for 5 pm.
Member Since: August 1, 2011 Posts: 28 Comments: 8041
Quoting stormwatcherCI:
Can someone tell me where this buoy is in relation to the COC of Irene if the winds are SW.

Station 42060
NDBC
Location: 16.333N 63.5W
Conditions as of:
Sun, 21 Aug 2011 18:50:00 UTC
Winds: SW (230°) at 7.8 kt gusting to 11.7 kt
Significant Wave Height: 6.6 ft
Dominant Wave Period: 10 sec
Atmospheric Pressure: 29.78 in and falling
Air Temperature: 78.1 F
Dew Point: 73.8 F
Water Temperature: 84.2 F


SE.
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2243. Gorty
She is moving WNW which I think is why the models shifted east with this run.
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2242. aquak9
Quoting Bluestorm5:
Man, the name of Irene just sound like one of those "major hurricane" names.

oh, you're still here. Good. Am I off the hook yet?
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Quoting Grothar:
The modesl on the 12 Z moved east, but on the 18Z moved slightly back west









of note is the heading at the end of a few of those...NW. perhaps trough #2 doesn't pull it north and ne quite as much. still lots of stuff in play.
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Quoting hotrods:
Irene looks to be pretty close to the Hurricane Centers points. I see the models have shifted again east,if irene stays on these points could have a shift once again back to west slightly, imo.


Irene is running north and east of her forecast points. Irene will go right over St. Croix and P.R.
The forecast points are well south of St. Croix.

But that doesn't mean Irene can't shift back to the west. But currently, she is staying to the right of her forecast path.
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Quoting earthlydragonfly:


Now that is some really irresponsible advice!!
Why?
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Man, the name of Irene just sound like one of those "major hurricane" names.
Member Since: August 1, 2011 Posts: 28 Comments: 8041
Quoting tcbob8794:
Any guesses on the 5PM intensity?


60 mph.

Quoting P451:


Starting to overcome dry air issues.
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Quoting ecflweatherfan:
My best guess is that the center of circulation at this point, based on radar, is on the southern part of the precipitation free "eye-like" feature... ESE of the easternmost point of St. Croix, moving W. Any thoughts?
you are correct slightly east
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Quoting TropicalAnalystwx13:
For those who like the Storm Alert music, I believe they only use it for major hurricanes.

We may here it anyways...
They used it for Hurricanes Ike and Gustav back in 08.They were both Cat two's.But it was understandable because both could've caused major damage.Ike caused cat 4 damage on the shore from it's extream storm surge.
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2234. P451
Quoting WeatherNerdPR:

Looking at radar, seems Irene is trying to form an eyewall, and is just east of St. Croix.


It does.

You're going to have one heck of an exciting night ahead of you.

Hope you're prepared...so you can just try to enjoy it as best you can.

Member Since: December 16, 2007 Posts: 7 Comments: 10202
Quoting tcbob8794:
Any guesses on the 5PM intensity?

IMO the same or maybe a tad stronger
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Hello all! Long-time lurker here.. Very rarely write on here. I've been a follower of this blog since 2004 and my fondest memory of the blog is the night Hurricane Wilma absolutely exploded into a Cat 5 while the HHunters were in the eye. It was breathtaking!

Anyways, there is a lot of confusion and near-chaos in here with the models' shift today. I think it's wisest to listen to what the Miami NWS office is saying as of 3pm today:

TROPICAL STORM IRENE CONTINUES TO MOVE TOWARD THE WEST NORTHWEST AT 17 MPH. ALTHOUGH THE STORM HAS WELL-DEFINED BANDING FEATURES IT STILL LACKS DEEP CONVECTION NEAR THE CENTER. THE FORECAST REASONING SINCE THIS MORNING IS VERY MUCH UNCHANGED. THERE IS A LOT OF UNCERTAINTY ON THE EXACT TRACK AND INTENSITY. HOWEVER...A HURRICANE LANDFALL IN THE SOUTHEASTERN US IS POSSIBLE, INCLUDING SOUTH FLORIDA.

THERE IS A LOT OF UNCERTAINTY ABOUT THE TEMPERATURE FORECAST FOR
THURSDAY SINCE A CHANGE IN THE FORECAST TRACK COULD CHANGE
CONSIDERABLE THE TEMPERATURES. NO CHANGES WERE DONE TO THE
EXTENDED TEMPERATURES BECAUSE OF THIS UNCERTAINTY AT THIS TIME

THE 12Z GFS SHOWS A MODEST SHIFT TO THE EAST IN THE TRACK OF THE
STORM. THIS NEW TRACK OF THE GFS IS MORE SIMILAR TO THE 00Z ECMWF
BUT THE ECMWF STILL KEEPS THE STORM CLOSER TO THE EAST COAST OF
FLORIDA THAN THE 12Z GFS. THE WINDS IN THE GRIDS MATCH WELL THE
00Z GFS...WHICH MATCHED VERY WELL THE 11 AM NHC ADVISORY TRACK. IT
IS PROBABLY BETTER TO SEE A TREND IN THE MODELS RATHER THAN 1 OR 2
SHIFTS BEFORE MAKING SIGNIFICANT CHANGES TO THE EXTENDED GRIDS AT
THIS TIME.

THE BIGGEST UNCERTAINTY WITH IRENE AT THE CURRENT TIME ARE A
SERIES OF TROUGHS THAT ARE FORECAST TO REACH THE EASTERN US IN THE
NEXT FEW DAYS. THE BIG QUESTION TO BE ANSWERED IS HOW THESE
TROUGHS OR WEAKNESSES WILL IMPACT THE TRACK OF IRENE...

Good advice there for all of us, regardless of where we live. Unless you're in the islands, there's plenty of time to watch the situation evolve.

::back to lurking::
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Quoting TropicalAnalystwx13:


Keep us informed with what they say.


Unfortunately I can't do that. Just have to wait until the information goes public at 5:00. But I will say, it doesn't appear they will be increasing her wind speeds just yet.
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Quoting presslord:


Tamp is the perfect place to be NOT to havre any interaction with this storm


Now that is some really irresponsible advice!!
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Quoting TropicalAnalystwx13:


I'm only 14, I don't know!

LOL!
but... you are smarter than me with tropics... I'm 16 -_-*
Member Since: August 1, 2011 Posts: 28 Comments: 8041
Quoting zerveftexas:
18z PLANFALF model takes Irene out to sea as a major hurricane......


I cannot find any information on this model. Is it new or experimental? Can you post a link?
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Quoting TropicalAnalystwx13:
For those who like the Storm Alert music, I believe they only use it for major hurricanes.

We may here it anyways...


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)....
Member Since: September 15, 2009 Posts: 525 Comments: 3701
2225. Grothar
The modesl on the 12 Z moved east, but on the 18Z moved slightly back west







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Can someone tell me where this buoy is in relation to the COC of Irene if the winds are SW.

Station 42060
NDBC
Location: 16.333N 63.5W
Conditions as of:
Sun, 21 Aug 2011 18:50:00 UTC
Winds: SW (230°) at 7.8 kt gusting to 11.7 kt
Significant Wave Height: 6.6 ft
Dominant Wave Period: 10 sec
Atmospheric Pressure: 29.78 in and falling
Air Temperature: 78.1 F
Dew Point: 73.8 F
Water Temperature: 84.2 F
Member Since: Posts: Comments:
Any guesses on the 5PM intensity?
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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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