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 TropicalAnalystwx13:
Irene should continue north of the forecast points as we progress through today...Puerto Rico, you may have a hurricane to contend with soon.


If she does, will she get turned out before Fla?
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Quoting rkay1:
Hey guys? Do you hear that? Sounds like tear drops falling from our FL bloggers.  After days of direct hits from our ever so reliable computer models, it seems Irene trolled you.  "...more north..." ..."cone of hope is further east..." these words must be like daggers.  Oh well, always next year right? ;) Hope you kept the receipts for the pallets of water bottles you guys bought yesterday.

What are you looking at? Cone looks the same to me at 11 AM....
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Member Since: July 3, 2005 Posts: 428 Comments: 129814


=\ yikes.
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It has definitely consolidated since yesterday, doesn't take up the entire state of Texas any longer.

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84 hrs...

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There you have it! The latest GFS run hot off the press, showing it just north of Hispaniola!!
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yes...please point out for us the humor in a tropical system striking this
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This storm is a bahamas storm and not florida unless it weakens alot over Hispaniola... best U.S. chance is S-N Carolinas.
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Quoting InTheCone:
72 hrs...



If Irene goes over Haiti, game over. If it skirts north, Savannah better batten down their plantations!
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Yeah, a big northeastern shift on the 12Z GFS vs. the 6Z:

Prior (06Z) run at 78 hours:




Latest (12Z) run at 72 hours:



Hopefully sparing Cuba and FL and hopefully the Bahamas too. Early days of course.
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Quoting emcf30:


I believe so by looking at the MIMIC

That does not show the actual path of the storm. It is a simulation based on the projected path of the storm.
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Quoting NCHurricane2009:


It looks like the broad center is heading straight to Puerto Rico...but Irene hasn't been able to strengthen and is running out of time to become a hurricane before Puerto Rico. If convective bursting doesn't consolidate this center tonight...I don't see this becoming a hurricane before Puerto Rico....


The center isn't THAT broad. Yes, it isn't a perfect consolidated circle, but it isn't very elongated either. We should see strengthening commence soon, if it hasn't started already.
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559. MZT
Quoting Walshy:


Rain Scale:
1 inch - Grass is turning greener.
3 inches - Hefty downpours.
5 inches - Creek flooded.
7 inches - Basement flooded.
11+ inches - Raging rivers.
I'd agree with tat. And Floyd dumped 20 inches in parts of N.C.
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Latest GFS has Irene hugging N coast of Hisp. looks like center reforms....and over water NE coast of cuba...never crosses cuba...still moving wnw...
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The G-4 Sniff and some more Guidance info will help solute a better Track in round 30-36 Hours.

Member Since: July 3, 2005 Posts: 428 Comments: 129814
Quoting InTheCone:
63 hrs...

63 hours. Trough lifting out fast!! Yikes.
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@72HR looks like Bermuda High is winning some ground as the C CONUS high backs away to make way to the next TROF which should make Irene have a more northerly component.

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Based on the new 12Z GFS looks like track on north side of DR. I expect major Hurricane to affect the Bahamas and far eastern Florida up to Savanna area maybe Cat 3 or stronger. The new 12Z data is now in better agreement with the HWF & ECMWF path for the last three days. Both these model bring Irene to a very dangerous high end cat 4 as it approaches SE Florida.
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Quoting osuwxguynew:
Appears that the GFS and other recent models are prefering an eastern FL or SC/GA/NC landfall. However, the models can just as easily switch back west or continue further east. I'm interested to see after the G-IV research mission goes out and gets upper air data this evening. Tonights models will probably be a bit more accurate.


That data wont help much till Weds when its near Cuba-Bahamas cause of the trough moving out.. we need to see how much ridging builds back in over the bahamas
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Quoting Dakster:


Stay safe and let us know how things go.


A similar experience to then TS Jeanne of 04 is what I'm expecting. Wind, rain, no power. And a lot of lightning.
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GFS basically depicting the worst case scenario. Little land interaction with bridged high pressure towards the north.
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Member Since: June 29, 2009 Posts: 13 Comments: 5315
Quoting Drakoen:
Looks like much less interaction with Hispaniola on this GFS run.


Not likely. Moving more NW, ever since center relocation to the north. This could even miss Hispaniola if it jogs further north.
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Quoting JRRP:



Right. Less interaction compared to dragging across almost the entire length of Hispaniola.
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545. JRRP
Quoting emcf30:


I believe so by looking at the MIMIC

looks like a bit more west
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Quoting WxLogic:
45HR:



Bermuda High starting to build back W as the TROF lifts.
excuse my weather ignorance, but does that mean that irene will be pushed towards the west? and if so, do you have any idea when that high pressure will build back in and how far it will build to the west? tia!
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Quoting HurricaneSwirl:
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 21 AUG 2011 Time : 144500 UTC
Lat : 16:59:03 N Lon : 63:08:00 W


CI# /Pressure/ Vmax
3.1 / 999.1mb/ 47.0kt


Final T# Adj T# Raw T#
2.7 2.5 2.5

Center Temp : -31.4C Cloud Region Temp : -45.3C

Scene Type : CURVED BAND with 0.33 ARC in LT GRAY
Maximum CURVED BAND with 0.88 ARC in LT GRAY
at Lat: 17:46:48 N Lon: 63:07:48 W

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : FLAG


C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 105km
- Environmental MSLP : 1012mb

Satellite Viewing Angle : 24.1 degrees
------------------------------------------------- ----------

Silly CIMSS. And that's why you don't completely rely on CIMSS and their products.


LOL.
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Quoting TropicalAnalystwx13:
Irene should continue north of the forecast points as we progress through today...Puerto Rico, you may have a hurricane to contend with soon.


It looks like the broad center is heading straight to Puerto Rico...but Irene hasn't been able to strengthen and is running out of time to become a hurricane before Puerto Rico. If convective bursting doesn't consolidate this center tonight...I don't see this becoming a hurricane before Puerto Rico....
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Quoting wxhatt:


It's going to move EAST of Florida now, so you should be just fine with now effects.


What makes you so certain Irene will miss Florida? That is, aside from living in North Carolina? ;-)
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UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 21 AUG 2011 Time : 144500 UTC
Lat : 16:59:03 N Lon : 63:08:00 W


CI# /Pressure/ Vmax
3.1 / 999.1mb/ 47.0kt


Final T# Adj T# Raw T#
2.7 2.5 2.5

Center Temp : -31.4C Cloud Region Temp : -45.3C

Scene Type : CURVED BAND with 0.33 ARC in LT GRAY
Maximum CURVED BAND with 0.88 ARC in LT GRAY
at Lat: 17:46:48 N Lon: 63:07:48 W

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : FLAG


C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 105km
- Environmental MSLP : 1012mb

Satellite Viewing Angle : 24.1 degrees
------------------------------------------------- ----------

Silly CIMSS. And that's why you don't completely rely on CIMSS and their products.
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72 hrs...

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538. wpb
Quoting InTheCone:


Not running for awhile yet.
please post when you start recieving them

thanks
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Quoting WeatherNerdPR:

Rain scale:
1 inch- Why is it raining so much?
3 inches- OMG is the street flooded?
5 inches- The river's CRAZY!
7 inches- Gotta get the hell outta here!
9 inches- THE STREET IS COLLAPSING! OMFG!
11+ inches- MY HOUSE IS FLOODED!


Rain Scale:
1 inch - Grass is turning greener.
3 inches - Hefty downpours.
5 inches - Creek flooded.
7 inches - Basement flooded.
11+ inches - Raging rivers.
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Appears that the GFS and other recent models are prefering an eastern FL or SC/GA/NC landfall. However, the models can just as easily switch back west or continue further east. I'm interested to see after the G-IV research mission goes out and gets upper air data this evening. Tonights models will probably be a bit more accurate.
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Quoting LongIslandXpress38:


Irene is going to die an honorable death over the luxurious community of Port Au Prince...


Very cold , ain't funny!
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533. JRRP
Quoting Drakoen:
Looks like much less interaction with Hispaniola on this GFS run.

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Quoting Patrap:
Floater - Rainbow Color Infrared Loop

Thanks so much to those of you, like Patrap here, who post only links to animations (and links to You Tube) and do not insert the actual clips in the blog. Those of us with slow internet speeds (cost or lack of availability of high speed) are very grateful. When the blog is cooking during times like today, it makes the "refresh" actually possibly. Even multiple still images in a single post are problematical. We, of the internet underclass, do salute you. (And hope others take note!)
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IRENE IR Loop
Member Since: July 3, 2005 Posts: 428 Comments: 129814
Quoting TropicalAnalystwx13:
Irene should continue north of the forecast points as we progress through today...Puerto Rico, you may have a hurricane to contend with soon.

I'm pretty sure she's gonna be 70-75mph when she makes her closest approach.
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529. MZT
Quoting HurricaneSwirl:
So, if it goes north of the islands, is it possible that it recurves before hitting the East Coast? I know a lot of experts were saying yesterday that there was almost no chance of it.
Pfftt.. Cones get moved, especially 5 days out. Nothing is set in concrete. We really need to see this clear Hispanolia and get down to 3 day forecasts to have a decent idea where it goes.

Odds of an east coast landing somewhere do look pretty good though. Hopefully it'll bring rain where needed and not flood places too badly.
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Quoting WeatherNerdPR:

It's quite possible they did or will, we're in a Hurricane Warning for Pete's sake! lol


Stay safe and let us know how things go.

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Quoting wpb:
can our model guy post hmrf 12z postions

thanks


Not running for awhile yet.
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Quoting Floodman:


Are we about to go to work?


I am still working from the last round, but the well will run dry very soon if it doesn't get replenished. To say we have been sweating hard since '08 is an understatement.

I hope you are about to go back to work in a big way. Do me a favor, adjust 'em low. ;-D
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Quoting Drakoen:


The 500mb heights are increasing to the north of Irene as she is just north of Hispaniola. Dangerous setup.

yes it is.

gonna be interesting how far west it takes it. S. FL could be looking at a major with that setup. anywhere on the east coast as well.
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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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