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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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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Quoting HurricaneSwirl:


They usually don't because they round the knots and then convert them, and then round them again. Let's say they found 48 knots. They would round that to 50 knots, convert it to 57.6 mph, and round that up to 60 mph. If they found 44 knots, they would round it to 45 knots, convert it to 51.8 mph, and then round that to 50 mph.

Although they do use it if they feel 50mph or 60 mph are too low or high respectively. Link



thank you
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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


In Wilmington, our kids dont start school until Thursday..they might be delayed though..stay safe down there and use your own judgement..
Member Since: August 19, 2006 Posts: 13 Comments: 15706
Quoting Drakoen:


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


Indeed... which forces her on that WNW track for a while longer.
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Dropsonde finds 1007mb at the surface....


...55 miles from the center.
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518. wpb
can our model guy post hmrf 12z postions

thanks
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63 hrs...

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Quoting TropicalAnalystwx13:


Yay!


Wooohooo.....

By the way...I have made a couple of notes with latest visible. This storm indeed continues to have a broadly organized center elongated N to S. If Irene does not tighten up to the north before getting to Hispaniola...it will get disrupted and stay broad/weak and take a track something like the GFDL....graze SW FL and enter the GOM...

....However...if Irene does tighten up to the north before Hispaniola...then this will take solutions like the Euro or GFS (east FL and east coast storm)....

...the next hours are critical...I am looking for a solid convective burst in the organized comma that comprises Irene's north side for a once-and-for-all consolidation of Irene's center toward the north. If this doesn't happen before Hispaniola...weaker and more south track likely....


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Quoting InTheCone:
Right on the north coast....



Irene is going to die an honorable death over the luxurious community of Port Au Prince...
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Looks like trough is a bit further east along with ridge than in previous runs of GFS.
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Quoting Pensa2woodtx:
...So will the winds be at hurricane force when it gets to Ames,Iowa...LOL


There is so much hot air being thrown around there, it wouldn't surprise me if it generated its own Hurricane...
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Quoting Tazmanian:



they dont do 55mph winds any more i dont think can any one help me out on this part plzs


i think they go with 60mph


They usually don't because they round the knots and then convert them, and then round them again. Let's say they found 48 knots. They would round that to 50 knots, convert it to 57.6 mph, and round that up to 60 mph. If they found 44 knots, they would round it to 45 knots, convert it to 51.8 mph, and then round that to 50 mph.

Although they do use it if they feel 50mph or 60 mph are too low or high respectively. Link
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Irene should continue north of the forecast points as we progress through today...Puerto Rico, you may have a hurricane to contend with soon.
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Quoting WxLogic:
@54HR Bridge trying to get going, but should have a hard time at it:



The 500mb heights are increasing to the north of Irene as she is just north of Hispaniola. Dangerous setup.
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Quoting barotropic:
12z gfs still running...big shift...brings irene wnw barely going thru haiti...and exiting central N coast.
where are our model image posters...slacking :)
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Quoting ncstorm:


Have they cancelled school yet..I would think they should have done that yesterday..

It's quite possible they did or will, we're in a Hurricane Warning for Pete's sake! lol
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Quoting stormpetrol:
Irene moving due west again imo , lets see if the new center fix confirms


I believe so by looking at the MIMIC
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Quoting coffeecrusader:
What time does Levi wake up. It would be nice to get an analysis from someone who is educated and not a wishcaster. Its amazing watching this board....

Its going to Miami (guess what their from Miami)
Its going to North Carolina (from NC)
Its going to the Panhandle (from Pensacola)
Its going to Texas (from Texas)

get the picture
...So will the winds be at hurricane force when it gets to Ames,Iowa...LOL
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@54HR Bridge trying to get going, but should have a hard time at it:

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Right on the north coast....

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Quoting scottsvb:
Its right on my forecast path from yesterday...the models initialized this too far south over the past few days and it did a jog WNW this morning.

This is why I always tell people that us METS dont look at long range models... Florida isn't out of the woods yet as its still 5 days off.. but the pattern shows more of a bahamas-Carolinas threat.



this is my forecast track, the one that counts
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Quoting scottsvb:
Its right on my forecast path from yesterday...the models initialized this too far south over the past few days and it did a jog WNW this morning.

This is why I always tell people that us METS dont look at long range models... Florida isn't out of the woods yet as its still 5 days off.. but the pattern shows more of a bahamas-Carolinas threat.
I don't think they initialized wrong, the center kept relocating/reorganizing further north
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Quoting WxLogic:
45HR:



Bermuda High starting to build back W as the TROF lifts.
Is there a reason you look at the 500 vort chart as opposed to the 850? Is it because of the strength of the storm? Because the 850v and 500v depict the high and the trof differently.
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Quoting Drakoen:
Looks like much less interaction with Hispaniola on this GFS run.


Might end up east of the 06z Run.
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TS IRENE on Guidance, on centerline

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Quoting Abacosurf:
thank you. Even the south end of models...


Some of the people on here need to take some Valium... they seem to try to keep second guessing the experts based on their 5 minute observations.

So far the Vortex plots are right on the forecast track.
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Quoting GainesvilleGator:
Irene is the only system that can travel West & end up WNW or NW or where it was. It looks to be pulling more north from LLC relocations. Does anyone really think that Irene will transverse the Island of Hispaniola?


See post 489
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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!


Have they cancelled school yet..I would think they should have done that yesterday..
Member Since: August 19, 2006 Posts: 13 Comments: 15706
Quoting VAbeachhurricanes:
Sooo southwest winds NW of the center fix? that doesn't make any sense.


That's what I was saying- S and SW winds that far north of the vortex don't make sense. Could be multiple vortexes in a broader circulation. Seems like a bad center fix.
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Quoting scottsvb:
Its right on my forecast path from yesterday...the models initialized this too far south over the past few days and it did a jog WNW this morning.

This is why I always tell people that us METS dont look at long range models... Florida isn't out of the woods yet as its still 5 days off.. but the pattern shows more of a bahamas-Carolinas threat.
Met? Last year you were telling me that ASCAT doesn't measure winds at the surface, but at the 925mb level.
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good news for haiti
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Irene is the only system that can travel West & end up WNW or NW or where it was. It looks to be pulling more north from LLC relocations. Does anyone really think that Irene will transverse the Island of Hispaniola?
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12z gfs still running...big shift...brings irene wnw barely going thru haiti...and exiting central N coast.
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Looks like she is back to moving due west again, for now.
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Looks like much less interaction with Hispaniola on this GFS run.
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Its right on my forecast path from yesterday...the models initialized this too far south over the past few days and it did a jog WNW this morning.

This is why I always tell people that us METS dont look at long range models... Florida isn't out of the woods yet as its still 5 days off.. but the pattern shows more of a bahamas-Carolinas threat.
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Quoting ncstorm:
tweet from Jim --thats a lot of rain for those folks
JimCantore Jim Cantore
#PuertoRico expect 40-60mph winds and 6-12 inches of rain tonight. Given how wet it's been flooding risk HIGH
9 minutes ago

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!
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Quoting TampaCat5:

What do the white dots mean?


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

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Quoting Amnesobel:
Jinkies lots to catch up on. I may or may not be present in a bit. Lots and lots to read

Feel free to ask as many question you want, we wont bite.
Member Since: September 30, 2007 Posts: 9 Comments: 15940
New tropical wave approaching the eastern atlantic
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Sooo southwest winds NW of the center fix? that doesn't make any sense.
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Moving W to WNW (at times).
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Is it still to soon to get concerned for NE (St. Augustine) Fl? Tested my generator, keep window protection pre made in the shed. Which is more likley to blow over, Big pine or big oak trees
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Quoting WxLogic:
45HR:



Bermuda High starting to build back W as the TROF lifts.


Interesting.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
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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. Would the high from the east build back in to push it west into the East Coast or something?

Questions aside, looks like I'm on the east side of the storm according to the latest models. Drought might have to stick around a little longer.
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Quoting coffeecrusader:
What time does Levi wake up. It would be nice to get an analysis from someone who is educated and not a wishcaster. Its amazing watching this board....

Its going to Miami (guess what their from Miami)
Its going to North Carolina (from NC)
Its going to the Panhandle (from Pensacola)
Its going to Texas (from Texas)

get the picture
Then don't add to the confusion and enjoy today.
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Quoting Orcasystems:




On track
thank you. Even the south end of models...
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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.