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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3023. Dakster
Quoting Neapolitan:
Looks like St. Croix is dead-center of Irene's eye -- er, roughly circular area of comparatively light winds, low precipitation, and sinking air that encompasses the center of the storm's rotation.


ROFLMAO...
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Quoting Drakoen:
Just in:



Holy...
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3020. Levi32
Still NNW wind and down to 998.2mb:

This is 30 minutes old though - the high-density obs that are coming in.

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Quoting chrisdscane:
dont kill me wishacaster look at the visible is that a SW or sws jog just askin


Nah, Levi explained this earlier. The big hole in the middle isn't the COC. The hook on the right side of that hole is. The rest of the hole is a dry spot. Since the hook, or the LLC, is on the right side, that means the dry spot will rotate around it to the west, resulting in the illusion of the "eye" (which really doesn't exist yet) moving WSW or SW. I didn't catch it at first either.
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3018. Seastep
Waiting on that E wind out of St. Croix to show a center to the S.

NNW, atm.

Center is due E of St. Croix. Maybe even a tad N of due E.

How small do those that think it is S think the COC is?

5 miles wide?
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Quoting charlottefl:


Why is that initialized at 1008mb?


Global models aren't great at showing the actual pressure of tropical systems.
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Quoting amd:


a little further north than that. Two buoys in st croix with the most recent updates have nnw @ 330 degrees around 17.75 N. This suggests that the center is approaching 17.8 or 17.9 degrees North.



With you on that amd. And that Microwave pass supports this as well.
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Quoting Drakoen:
Just in:


O-O-OH M-MY G-G-GOD...
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting Stormchaser2007:
Following the ECMWF

36 hours

may make northerly turn sooner in this run. IMO
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Quoting TropicalAnalystwx13:
Irene has strengthened...




yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115439
Looks like St. Croix is dead-center of Irene's eye -- er, roughly circular area of comparatively light winds, low precipitation, and sinking air that encompasses the center of the storm's rotation.
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Quoting BahaHurican:
00Z is 8 p.m. isn't it? Why r they taking off early?
since she is nearby they may be waiting for the center to finish moving over the st croix to take off
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Quoting 7544:
gfs running now whos posting
you
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srbv3 and CHSV3 stations both reporting pressure of 29.54mb in st. croix, with winds still out of the north so center had not passed yet. However there is a lag of 45 minutes before the readings are appearing at the web site of www.ndbc.noaa.gov.

here is a web site to convert to millibars:

http://www.csgnetwork.com/pressinmbcvt.html

Doing the conversion this turns out to be 1000.33Mb and still dropping.
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Irene has strengthened...
Member Since: July 6, 2010 Posts: 113 Comments: 32720
Seeing as I usually storm chase and we occasionally have to raise the radar to see further away I will lend this advice. Some of you are asking Levi about the center and I encourage you to pull up the radar and raise the elevation to 1.45 and you will see what he's talking about. You can see in the last frames as it gets closer the LLC that he is referring to.

Hope that helps
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3004. amd
Quoting USAFwxguy:
17.5, 64.5

roughly.


a little further north than that. Two buoys in st croix with the most recent updates have winds out of the NNW @ 330 degrees around 17.75 N. This suggests that the center is approaching 17.8 or 17.9 degrees North.

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3003. Drakoen
Just in:

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3002. Dakster
Quoting StormJunkie:


Yep, sort of expecting that W motion to continue for 2-6hrs before it starts to pull just a hair north of 270.


What color hair?
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Quoting Stormchaser2007:
998 mbs and dropping


Stronger still...
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting NICycloneChaser:


Take off scheduled for 7:00pm EDT.
00Z is 8 p.m. isn't it? Why r they taking off early?
Member Since: October 25, 2005 Posts: 19 Comments: 22687
Quoting charlottefl:


Well I was just thinking more like Friday afternoon as opposed to Thurs Night. Has Irene been moving faster than projected?

Current forecast has Irene up near Orlando by 2pm Friday afternoon. Of course, this can and will change over time.
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Quoting WxLogic:
18Z GFS Init... but already running for a bit.



Why is that initialized at 1008mb?
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Just came inside from hot, miserable garage. Sorted my hurricane shutters. They are now ready to put up. Thinking about putting up a couple tonight, couple tomorrow night, etc. Then just leaving them up until the end of season! LOL
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2995. Patrap
San Juan Radar
NEXRAD RadarType
Velocity Azimuth Display Wind Profile

Member Since: July 3, 2005 Posts: 427 Comments: 129452
998 mbs and dropping

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Quoting JrWeathermanFL:
Hmm. Wondering if Irene will become a hurricane at all.

It's organizing, probably nearing hurricane strength IMO.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting shawn26:
I rely heavily on what Levi says.
Eye Dew Two!
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to me looks like SE Florida if the track does not change that TS watches would be issued sometime late tomorrow
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Quoting Patrap:
She has come over the z-hill fully to the PR Doppler,,but itsa still on that 270 vector seems SJ.


Yep, sort of expecting that W motion to continue for 2-6hrs before it starts to pull just a hair north of 270.

Chrisd; you're killin' me...lol
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dont kill me wishacaster look at the visible is that a SW or sws jog just askin
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Following the ECMWF

36 hours

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2987. Levi32
Quoting weatherxtreme:
Levi,

I want to personally Thank You for all of your analysis and tidbits on this blog! I really respect a lot of what you do and say! Keep up the great work here.


Well thank you, and you're welcome. I'm glad I can be of some service.
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The National Hurricane Center themselves noted that Tropical Storm Irene is becoming better organized...Should see a stronger system at 8/11 PM.

IRENE IS GRADUALLY BECOMING BETTER ORGANIZED IN ITS APPEARANCE ON
SATELLITE IMAGES...WITH CURVED BANDS BECOMING BETTER DEFINED.
Member Since: July 6, 2010 Posts: 113 Comments: 32720
2985. KEEPEROFTHEGATE (Mod)
Quoting Patrap:
deciding this night left or right her fate
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Quoting Seflhurricane:
very unlikely


Yes, extremely unlikely S.E. Florida will be out of the cone anytime soon.
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2983. WxLogic
18Z GFS Init... but already running for a bit.

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Quoting oceanblues32:
So as i see the track keeps shifting east so most likely tomorrow morning will wake up and we here in southeast florida will be out of cone maybe?
doubt it looks like this one is going right over us buy fuel
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Quoting ProgressivePulse:



I was surprised the NHC didn't shift more in line with the TVCN, especially after two consecutive shifts eastward today. Leads me to believe that they have a little more confidence in their current forecast than is being advertised.


I'm thinking about you over there in Jupiter. I am not far from you. Things continue to improve as far as our interests are concerned. I have ever reason to expect that trend will continue.
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Quoting Sfloridacat5:
T

This is definitely not strange given the current forecast path. Irene is currently forecast to move into Southeast Florida Thursday night.



Well I was just thinking more like Friday afternoon as opposed to Thurs Night. Has Irene been moving faster than projected?
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Hmm. Wondering if Irene will become a hurricane at all.
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Quoting ronmil:

The first bands or Irene approaching Maunabo, Puerto Rico (SE corner) at 3:30pm...

Amazing!
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting oceanblues32:
So as i see the track keeps shifting east so most likely tomorrow morning will wake up and we here in southeast florida will be out of cone maybe?
very unlikely
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2976. breald
Quoting StormJunkie:


I'm in school for a year so that I can pass it; hence the associates in Avionics as well...They better teach me everything I need to know ;) The sad thing is that Boeing requires an A&P as well in order to work flight line. Would much rather end up somewhere like Gulfstream, or better yet...Scaled Composites. Not sure I'm a West Coast man though. I sort of like the Holy City.


He went to FCCJ.(Jacksonville) They had a really good aviation program there. Good luck with your studies.
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Ireeeene, come on Baby!! Give me all you've got.... I'm ready for Ya.... Yiiiiirrrraaaaaa!!!!


Sorry, Tropical storm madness....







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2973. rod2635
myrtle beach
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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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