Dr. Jeff Masters' WunderBlog

Dangerous Tropical Storm Irene headed for the Dominican Republic
Posted by: Dr. Jeff Masters, 2:38 PM GMT on August 21, 2011 +48
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
Categories: Hurricane
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2551. shawn26 8:50 PM GMT on August 21, 2011    
not much of a shift considering all of the model shift
Member Since: September 3, 2009 Posts: 0 Comments: 203
2554. Torgen 8:50 PM GMT on August 21, 2011    
Quoting breald:


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


Maybe it was a PLANFALF category 1...
Member Since: June 3, 2010 Posts: 0 Comments: 321
2555. Levi32 8:51 PM GMT on August 21, 2011    
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.
Member Since: November 24, 2005 Posts: 586 Comments: 25459
2556. Bretts9112 8:51 PM GMT on August 21, 2011    
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.
Member Since: June 22, 2010 Posts: 0 Comments: 140
2557. TropicalAnalystwx13 8:51 PM GMT on August 21, 2011    
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
Member Since: July 6, 2010 Posts: 89 Comments: 25347
2558. Dunkman 8:51 PM GMT on August 21, 2011    
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.
Member Since: February 6, 2010 Posts: 0 Comments: 214
2559. interstatelover7165 8:51 PM GMT on August 21, 2011    
5 DAY Forecast
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2561. masonsnana 8:51 PM GMT on August 21, 2011    
Quoting TropicalAnalystwx13:
Cone still needs to be shifted east..
You should call them!
Member Since: February 14, 2004 Posts: 2 Comments: 513
2562. 900MB 8:51 PM GMT on August 21, 2011    
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!
Member Since: June 11, 2006 Posts: 0 Comments: 609
2563. islander101010 8:51 PM GMT on August 21, 2011    
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
Member Since: September 11, 2010 Posts: 0 Comments: 2968
2564. MZT 8:51 PM GMT on August 21, 2011    
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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2565. stormwatcherCI 8:51 PM GMT on August 21, 2011    
Heading has shifted from 290 to 285
Member Since: October 9, 2008 Posts: 0 Comments: 8043
2566. Grothar 8:51 PM GMT on August 21, 2011    
img src="">
Member Since: July 17, 2009 Posts: 57 Comments: 19553
2567. JLPR2 8:52 PM GMT on August 21, 2011    
Well now, I see an S over central PR.
Member Since: September 4, 2007 Posts: 7 Comments: 7487
2568. washingtonian115 8:52 PM GMT on August 21, 2011    
Quoting CaicosRetiredSailor:
Still

9-0-0
Believe me.That's gonna change.
Member Since: August 14, 2010 Posts: 5 Comments: 10675
2570. NICycloneChaser 8:52 PM GMT on August 21, 2011    
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.
Member Since: August 10, 2010 Posts: 2 Comments: 1957
2571. number4steel 8:52 PM GMT on August 21, 2011    
fran was a cat3, proceded by bertha i think , turned out to be on heck of a one two punch
Member Since: August 29, 2010 Posts: 0 Comments: 62
2572. WeatherNerdPR 8:52 PM GMT on August 21, 2011    
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: 5464
2573. scott39 8:53 PM GMT on August 21, 2011    
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: 6207
2574. 954FtLCane 8:53 PM GMT on August 21, 2011    
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.....
Member Since: September 30, 2008 Posts: 0 Comments: 1464
2575. BoroDad17 8:53 PM GMT on August 21, 2011    
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.
Member Since: September 5, 2008 Posts: 0 Comments: 121
2576. PrivateIdaho 8:53 PM GMT on August 21, 2011    
Quoting TropicalAnalystwx13:
Cone still needs to be shifted east..


You must have downloaded a copy of the REED model.
Member Since: August 29, 2010 Posts: 0 Comments: 5211
2577. PensacolaDoug 8:53 PM GMT on August 21, 2011    
Quoting shawn26:
not much of a shift considering all of the model shift


Just wait till the shift hits the fan!
Member Since: July 25, 2006 Posts: 0 Comments: 4828
2580. MZT 8:54 PM GMT on August 21, 2011    
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"
Member Since: September 24, 2005 Posts: 0 Comments: 775
2581. tropicfreak 8:54 PM GMT on August 21, 2011    
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: 6566
2583. HurricaneDean07 8:54 PM GMT on August 21, 2011    
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
Member Since: October 3, 2010 Posts: 39 Comments: 4054
2584. TybeeJoe 8:54 PM GMT on August 21, 2011    
Quoting JrWeathermanFL:
I think Irene will be like a mix of Hugo and David.
I live in Savannah...that's not good
Member Since: August 15, 2008 Posts: 0 Comments: 6
2585. lottotexas 8:55 PM GMT on August 21, 2011    
Anyone seen Miami Hurricane today?
Member Since: December 3, 2010 Posts: 0 Comments: 4
2586. TropicalAnalystwx13 8:55 PM GMT on August 21, 2011    
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.
Member Since: July 6, 2010 Posts: 89 Comments: 25347
2587. NCHurricane2009 8:55 PM GMT on August 21, 2011    
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: 277 Comments: 3357
2588. HCW 8:55 PM GMT on August 21, 2011    
Member Since: August 10, 2002 Posts: 0 Comments: 1280
2589. NICycloneChaser 8:55 PM GMT on August 21, 2011    
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.
Member Since: August 10, 2010 Posts: 2 Comments: 1957
2590. thelmores 8:55 PM GMT on August 21, 2011    
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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2591. Grothar 8:55 PM GMT on August 21, 2011    
GFS ensemble model

Member Since: July 17, 2009 Posts: 57 Comments: 19553
2592. PRweathercenter 8:55 PM GMT on August 21, 2011    
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
Member Since: July 21, 2010 Posts: 58 Comments: 916
2593. Levi32 8:56 PM GMT on August 21, 2011    
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.
Member Since: November 24, 2005 Posts: 586 Comments: 25459
2594. tropicfreak 8:56 PM GMT on August 21, 2011    
Quoting TropicalAnalystwx13:
Cone still needs to be shifted east..


I agree.
Member Since: September 2, 2006 Posts: 110 Comments: 6566
2595. AllStar17 8:56 PM GMT on August 21, 2011    
If Harvey continues on a heading between about 287 and 290...it will just graze Hispaniola.
Member Since: June 29, 2009 Posts: 13 Comments: 5135
2596. wolftribe2009 8:56 PM GMT on August 21, 2011    
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.
Member Since: July 22, 2010 Posts: 6 Comments: 752
2597. HurricaneDean07 8:56 PM GMT on August 21, 2011    
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
Member Since: October 3, 2010 Posts: 39 Comments: 4054
2598. SavannahStorm 8:56 PM GMT on August 21, 2011    
Gusting to 60 on the St. Croix northern coast. Pressure still dropping.

Member Since: September 22, 2005 Posts: 18 Comments: 2135
2599. Gorty 8:56 PM GMT on August 21, 2011    
The NHC is being very conservative.
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2600. MrstormX 8:57 PM GMT on August 21, 2011    
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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2601. robj144 8:57 PM GMT on August 21, 2011    
Quoting AllStar17:
If Harvey continues on a heading between about 287 and 290...it will just graze Hispaniola.


Harvey's coming back around? :)
Member Since: August 19, 2008 Posts: 0 Comments: 814

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About JeffMasters
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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