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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Member Since: Posts: Comments:
Quoting WeatherNerdPR:

Call me crazy, but it seems to have slowed down.


Nope, you aren't crazy.
Member Since: Posts: Comments:
‎Today, ‎August ‎21, ‎2011, ‏‎4 minutes ago
August 21, 2011 7:00 pm ADT
Location: 18.251N 64.763W
Wind Direction: ENE (70°)
Wind Speed: 33.0 knots
Wind Gust: 40.8 knots
Significant Wave Height: 10.5 ft
Dominant Wave Period: 10 sec
Atmospheric Pressure: 29.62 in (1003.1 mb)
Pressure Tendency: -0.07 in (-2.4 mb)
Air Temperature: 78.1°F (25.6°C)
Water Temperature: 84.2°F (29.0°C)

Member Since: Posts: Comments:
Quoting Bluestorm5:
931 mb at 90 hr. Little farther to east from last run.




how about posting some maps huh?
Member Since: May 21, 2006 Posts: 5091 Comments: 114765
Quoting Patrap:
..no mo speed speed Im almost there..



img src="http://radblast-mi.wunderground.com/cgi-bin/r adar/WUNIDS_map?station=JUA&brand=wui&num= 30&delay=5&type=N0Z&frame=0&scale= 0.750&noclutter=0&t=1313968015&lat=0&a mp;lon=0&label=you&showstorms=&map.x=4 00&map.y=240&centerx=323&centery=163&a mp;transx=-77&transy=-
77&showlabels=1&severe=0&rainsnow=&am p;ligh


tning=&smooth=1" style="max-width: 501px; ">



One more radar lovers gone......
Member Since: September 26, 2010 Posts: 0 Comments: 637
have the new model runs come out yet , and if they have have we seen any changes
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Quoting alvarig1263:


Just like Hurricane Alex last year. Pressures were lowering dramatically and if it had had a little bit more time over water, Alex would have rapidly intensified right before landfall. Good that didn't happen though. Let's see what happens with Irene...


That was different though - Alex was of monsoon origins, like Western Pacific systems. Irene is a genuine system, and so the winds and pressure should stay close together in tandem.
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3616. WxLogic
HWRF want to go out to sea from the looks of it

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931 mb at 90 hr. Little farther to east from last run.
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Looks like Irene is slowing down a bit.
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Quoting wunderkidcayman:
guys guys just comin back from a swim looking at thr PR radar you can see the eye clearly moving over St. Croix and is movin SSW look

Link
I believe it is just a tightening up of the center giving the appearance of a southerly component to the track whereas I believe the actual track is still true West.
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Quoting jennT:

actually, we're sitting in a weird serene place. it's quiet and not very rainy. I might rather a crazy thunderstorm...
Maybe because you are in the Eye?
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3611. xcool
Seflhurricane welcome...
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That dry air spot is getting smaller..Think this means there is an actual EYE forming now.
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Coffee ready and made for a late night as strengthening Irene passes over my home in PR while I am in NYC.

Hoping all is well while watching the updates. Stay safe and hunker down if you are in PR.
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Quoting TropicalAnalystwx13:


Somewhere between due west and west-northwest.

Call me crazy, but it seems to have slowed down.
Member Since: July 7, 2010 Posts: 0 Comments: 5630
Quoting CosmicEvents:
That's what I think as well. What effect if any do you see from the wind flow down the mountains into the cyclone?


If you mean the mountains in PR no effect IMO as PR is too small an island to do much damage to the circulation which is pretty well established now. Sinking air warms and dries as it sinks and that would not be good for a tropical system but I don't see that as an issue here.

Hispaniola is a different story altogether. Several issues there with very high terrain near 10,000 feet. Passage over that island for any appreciable period of time could decouple the storm. Even a close pass near the coast could disrupt the circulation on that one side due to interaction with land and friction.
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Think it's time for a new entry considering there are ~3575 comments.
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Quoting TropicalAnalystwx13:


Recon found a minimum central pressure so far of 995.4 mb. This means that the winds are likely around 60 mph, from what they have found so far. However, that is still a little low given the pressure, and further strengthening should occur tonight. Given its current heading, a direct landfall on Puerto Rico my mid-morning tomorrow is likely. After that, it seems that Irene will only scrape the northern coast of Hispaniola rather than cross the entire length. This means that we could be dealing with a stronger system in the long run.

Another thing to note is that, since Irene is farther north than originally predicted, the models have shifted more towards South Carolina and North Carolina.


Just like Hurricane Alex last year. Pressures were lowering dramatically and if it had had a little bit more time over water, Alex would have rapidly intensified right before landfall. Good that didn't happen though. Let's see what happens with Irene...
Member Since: September 2, 2008 Posts: 0 Comments: 744
Quoting charlottefl:


NHC knows what they're doing, if they need to adjust the track they will, but as long as your in the cone it's best to keep an eye on it. After all a storm is not a point on a map, and 200 miles is a lot of room for error.


Right, and the fact that there is already a south side error to the track from the last model consensus at T+6hours should be a reminder she could easily end up at either extreme end of the 5 day cone come end of week.
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3603. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting xcool:
Seflhurricane mail
Thanks:):):)
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Quoting WeatherNerdPR:
At what direction is this moving?


Somewhere between due west and west-northwest.
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938 mb storm on eastern side of Bahamas.
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Quoting jennT:

actually, we're sitting in a weird serene place. it's quiet and not very rainy. I might rather a crazy thunderstorm...


Your in St. Croix?
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one of the callers said about a hr ago that because of a deep trench around the island of st croix storms like to develop a eye right over the island.
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Quoting WeatherNerdPR:
At what direction is this moving?




is it moveing backwords?
Member Since: May 21, 2006 Posts: 5091 Comments: 114765
3595. KEEPEROFTHEGATE (Mod)
left she goes
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Quoting HurricaneIrene:


Mike, is she moving southwest on this satellite? 0_0.


I think its just the ragged eye changing shape and size.
But since mid afternoon, Irenes been on a more westerly (W to WNW) track.
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3593. KEEPEROFTHEGATE (Mod)
looks like she is chosing right
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Quoting Patrap:
..no mo speed speed Im almost there..





...Gotta be cool now gotta take care...
Member Since: October 26, 2003 Posts: 0 Comments: 363
At what direction is this moving?
Member Since: July 7, 2010 Posts: 0 Comments: 5630
Quoting Levi32:
A short-term due west jog does look to be ensuing on radar. It will be interesting to see if it stays that way and doesn't actually make landfall in PR. Regardless, Puerto Rico will get the worst of Irene, either way.


I am going to go offline as for sure power will be turned off by sections in PR as it occured in past events of landfall here.I am safe in my house with shutters. See you and the rest when power is back.
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Eyewall looks to be about half way complete NE, E, and SE Sides.
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Guys, the system isn't moving SW.. That's the dry slot being rotated counter-clockwise around the center. Irene is moving due W to WNW atm.
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Quoting charlottefl:


NHC knows what they're doing, if they need to adjust the track they will, but as long as your in the cone it's best to keep an eye on it. After all a storm is not a point on a map, and 200 miles is a lot of room for error.


Good advice.
Member Since: October 26, 2003 Posts: 0 Comments: 363
A lot of us saying she was moving west all afternoon, and took the heat for saying that.

Weather Channel just said she's building an eye wall?!
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3584. xcool
Seflhurricane mail
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The dry spot is starting to fill in.
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3582. Patrap
..no mo speed speed Im almost there..



Member Since: July 3, 2005 Posts: 421 Comments: 127636
3581. jennT
Quoting Seflhurricane:
st croix is taking a beating

actually, we're sitting in a weird serene place. it's quiet and not very rainy. I might rather a crazy thunderstorm...
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Quoting hurricanehunter27:
That dry air pocket actully helped set a format for the eye, you can tell cause its getting smaller.


Looks like it is just to the south of the western tip of St. Croix.
Member Since: October 9, 2008 Posts: 0 Comments: 8278
Station CHSV3 - 9751364 –
Christiansted Harbor, Virgin Islands
Pressure just went up slightly after bottoming
out at 996.5 mb

6:30 PM 996.7 mb
6:24 PM 996.6 mb
6:18 PM 996.5 mb
6:12 PM 996.5 mb
6:06 PM 996.6 mb

wind now SSW
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Quoting Levi32:
A short-term due west jog does look to be ensuing on radar. It will be interesting to see if it stays that way and doesn't actually make landfall in PR. Regardless, Puerto Rico will get the worst of Irene, either way.
and that is irregardless of a direct landfall or not ? :)

from merriam-webster.com
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3576. Ryuujin
Quoting Patrap:
Zoomed into the Vortex



But isn't that just a dry slot being thrown out or is that the actual enter of circulation? I just got home so I'm kind of lost
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Quoting TropicalAnalystwx13:


Do Not!

There is still a very high chance that Irene makes landfall in South Florida, and you need to prepare for Irene now!


Yeah you are right.....come to think of it, we are talking 50 miles here. It turns north 50 miles east, we don't get anything, it stays the coarse we get slammed. I can always put the gas in the cars if it misses, but it is better to be prepared ahead of time.
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3574. WxLogic
Quoting wpb:
thanks for the hmrf spots. ?does the gfdl start there runs later?


Yes after...
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Quoting Bluestorm5:
Hit the very tip of Hispaniola.


The run is out to 78 hours lol. You're a little behind.
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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.