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.

Links
Long-range radar out of Puerto Rico

Jeff Masters

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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?
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Quoting P451:


And...the cone shifts north.

Not surprised since she headed WNW all day and not West.


Still shows a hurricane over south Florida.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
fran was a cat3, proceded by bertha i think , turned out to be on heck of a one two punch
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Quoting Dunkman:


I don't know if anyone has pointed this out...too many comments, but the SHIPS uses the GFS for its track. I'd guess the reason it intensifies the storm much faster now is that the latest GFS run just skirts Hispanola and has Irene in a much more favorable environment for strengthening during the forecast period.


That's almost word for word what I suggested just after I made that post, lol.
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Quoting CaicosRetiredSailor:
Still

9-0-0
Believe me.That's gonna change.
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2567. JLPR2
Well now, I see an S over central PR.
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2566. Grothar
img src="">
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Heading has shifted from 290 to 285
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2564. MZT
Wonder if Dr Masters will post within the next hour... this is the first really ominous looking storm we've had this year.
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dang it personal doom level goes up ouch as for p. rico the so called north side of the eye wall should go right over patillias a little villiage on the se side of puerto rico fond memories of that area
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2562. 900MB
Wow. W/WNW motion and expected to stay that way for the next couple of days. Center is near St. Croix. It will hit PR.
That settles those questions for about 10 mins!
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Quoting TropicalAnalystwx13:
Cone still needs to be shifted east..
You should call them!
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5 DAY Forecast
Member Since: August 18, 2011 Posts: 0 Comments: 994
2558. Dunkman
Quoting NICycloneChaser:


That's the first time that SHIPS has shown real intensification. Slightly alarming.


I don't know if anyone has pointed this out...too many comments, but the SHIPS uses the GFS for its track. I'd guess the reason it intensifies the storm much faster now is that the latest GFS run just skirts Hispanola and has Irene in a much more favorable environment for strengthening during the forecast period.
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Quoting P451:
What Irene's center has done all day.... and is about to do again: It's wobbling and looping around itself.



This tricks you into focusing on a feature within the storm move west then wsw then jump back north.

That is the motion of a feature within the large scale rotation of the storm and not the forward heading of the storm itself.

The large scale rotation of the storm has kept a steady heading all day long. Started at St Kitts and is now moving actually a little north of St Croix and is heading towards the Eastern shores of PR.


If you think the storm is heading west or wsw... this because you have focused in on a small feature of the storm.


Look at any long range imagery. Compare the storms location now to where it was early this morning when maybe you felt it was going due west..... and you will clearly see that was not the case.


WNW to PR it has been going all day long.


And now it's strengthening.



Loopy Loop
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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!


IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT
DAYS 4 TO 5 SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE
FORECAST TIMES ARE 200 AND 250 MILES RESPECTIVELY.
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2555. 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.
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2554. Torgen
Quoting breald:


Fran was a cat 3 when it made landfall in NC.


Maybe it was a PLANFALF category 1...
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2551. shawn26
not much of a shift considering all of the model shift
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2550. ackee
Quoting stormpetrol:
Now that the eye has closed off it appears ST.Croix is dead center of the eye, but I still think it basically moving due west , 275 degrees at most, jmo.
do u see the centre south of PR or EAST
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2549. WxLogic
I agree with this shift... a gradual and not as sharp as some models are forecasting.

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Cone still needs to be shifted east..
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See...even the NHC 5 PM advisory says moving WNW...definitely WNW it is....
Member Since: September 15, 2009 Posts: 539 Comments: 3712
well I was close NHC 17.7N/64.4W , i said 17.5N/64.5W, thats roughly 12 miles off lat and 6 miles off long.
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Quoting Levi32:


Based on echo drifts and surface obs, I believe it is somewhere here:



Levi, the immortal question:

Is that trying to be an eyewall?
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At 17.7N, the center is exactly where radar shows it.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
The storm appears to have a lot of energy. Hopefully it runs into everything out there.
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2540. RickWPB
Well the cone shifted a bit east. Now instead of aiming at Miami, it's centered on West Palm Beach!

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Member Since: July 7, 2010 Posts: 0 Comments: 5725
Still

9-0-0
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting Levi32:


Based on echo drifts and surface obs, I believe it is somewhere here:

Yup.

Just ESE of St. Croix.

As a few were saying.
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2535. Levi32
The current motion should take Irene over a portion of Puerto Rico and then the northern part of the Dominican Republic.
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HARVEY LIVES! Why am I not surprised?
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2530. breald
Quoting lucreto:


Not to lessen your experience but Fran was in reality only a Cat.1 imagine a stronger storm


Fran was a cat 3 when it made landfall in NC.
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TROPICAL STORM IRENE DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 PM AST SUN AUG 21 2011

IRENE IS GRADUALLY BECOMING BETTER ORGANIZED IN ITS APPEARANCE ON
SATELLITE IMAGES...WITH CURVED BANDS BECOMING BETTER DEFINED. THE
CURRENT INTENSITY IS HELD AT 45 KT IN ACCORDANCE WITH OBSERVATIONS
EARLIER THIS AFTERNOON FROM THE AIR FORCE HURRICANE HUNTERS.
ANOTHER HURRICANE HUNTER PLANE IS SCHEDULED TO INVESTIGATE IRENE
AROUND 0000 UTC. WITH A WELL-DEFINED UPPER-LEVEL OUTFLOW
ANTICYCLONE SITUATED OVER THE STORM...THE PRIMARY IMPEDIMENT TO
STRENGTHENING OVER THE NEXT COUPLE OF DAYS SHOULD BE LAND
INTERACTION. IF IRENE MOVES OVER MORE OF HISPANIOLA OR OVER PARTS
OF EASTERN CUBA IT WILL LIKELY BE WEAKER THAN INDICATED
HERE...HOWEVER IF THE SYSTEM ENDS UP MOVING TO THE NORTH OF BOTH OF
THOSE LAND MASSES IT COULD STRENGTHEN MORE THAN EXPECTED. THE
OFFICIAL INTENSITY FORECAST IS SOMEWHAT HIGHER THAN THE LATEST LGEM
STATISTICAL-DYNAMICAL GUIDANCE.

THE FORWARD MOTION HAS SLOWED A BIT AND IS NOW NEAR 285/15. IRENE
CONTINUES TO BE STEERED BY THE FLOW ON THE SOUTH SIDE OF A
MID-LEVEL SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC. THE
WEST-NORTHWESTWARD MOTION IS LIKELY TO CONTINUE FOR 1 TO 2 DAYS
WHICH WOULD BRING THE CENTER NEAR OR OVER PUERTO RICO...AND NEAR OR
OVER THE DOMINICAN REPUBLIC. OVER THE NEXT FEW DAYS...A COUPLE OF
TROUGHS ARE FORECAST TO CREATE A WEAKNESS IN THE RIDGE NEAR THE
SOUTHEAST U.S. COAST WHICH SHOULD INDUCE A TURN TO THE RIGHT AROUND
DAY 3. SEVERAL OF THE RELIABLE TRACK GUIDANCE MODELS SUCH AS THE
ECMWF AND GFS HAVE SHIFTED EASTWARD FROM THEIR PREVIOUS RUNS AND SO
HAS THE DYNAMICAL CONSENSUS. THE OFFICIAL TRACK FORECAST HAS BEEN
SHIFTED A LITTLE TO THE RIGHT OF THAT FROM THE PREVIOUS ADVISORY
AND LIES ON THE WESTERN SIDE OF THE GUIDANCE ENVELOPE. IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT
DAYS 4 TO 5 SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE
FORECAST TIMES ARE 200 AND 250 MILES RESPECTIVELY.

FORECAST POSITIONS AND MAX WINDS

INIT 21/2100Z 17.7N 64.4W 45 KT 50 MPH
12H 22/0600Z 18.2N 66.6W 60 KT 70 MPH...INLAND
24H 22/1800Z 18.9N 69.3W 65 KT 75 MPH...INLAND
36H 23/0600Z 19.6N 71.5W 50 KT 60 MPH...INLAND
48H 23/1800Z 20.3N 73.5W 50 KT 60 MPH...OVER WATER
72H 24/1800Z 22.7N 76.7W 60 KT 70 MPH
96H 25/1800Z 25.5N 79.5W 75 KT 85 MPH
120H 26/1800Z 28.5N 81.5W 50 KT 60 MPH...INLAND

$$
FORECASTER PASCH
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting P451:


Emily followed XTRP for like three days LOL.

It is bar none my favorite not-a-model model.

If models have a gender, XTRP is male, while all the other models are female.

XTRP is quick, decisive, and never wavering.

You have to admire something of that stature.

XTRP is a model's model, an Adonis if you will.


XTRP is the Chuck Norris of not-a-model models.
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NHC is not buying tracks to SC...
Member Since: August 1, 2011 Posts: 28 Comments: 8075
Quoting stormwatcherCI:
HARVEY EMERGES OVER THE SOUTHERN BAY OF CAMPECHE...TROPICAL STORM WARNING ISSUED FOR A PORTION OF THE SOUTHERN COAST OF MEXICO...
4:00 PM CDT Sun Aug 21
Location: 18.6°N 93.8°W
Max sustained: 30 mph
Moving: WNW at 14 mph
Min pressure: 1007 mb


Wonder if he will reorganize and head for Texas.


Unfortunately (for drought resaons in Texas)...this won't happen..stiff steering to keep Harvey west-northwest...
Member Since: September 15, 2009 Posts: 539 Comments: 3712
I agree with the new track
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2523. ncstorm
Member Since: August 19, 2006 Posts: 13 Comments: 16225

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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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