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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1123. Walshy
Quoting Tazmanian:
932mb is a cat 5 lol


Was that suppose to make me laugh too? : /
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where is the high and is it building back in?
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Quoting Bluestorm5:
Very close to Charleston at 120 hr out. 933 mb. Again, people should not pay attention to this run.


People should pay attention to every run and never fixate on one run or one model at this stage of tracking.

Quoting Joshfsu123:



If it is stacked, once it cycles out the dry air, I would expect to see some intensification later tonight into tomorrow morning. System seems ready to go.


I would not be surprised if it starts intensifying even a little sooner then that. Yesterday convection really started to build around this time so she may not even wait for the diurnal cooling to start. Will just have to watch and see how this plays out with mountain interaction...
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Quoting HurricaneDean07:
Irene, Bum bum bum BUM


Looky what we got here, GFS 12Z Jose coming...
You just summarized downtown Miami, lol.
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1117. nigel20
Quoting Levi32:


Part of it was the strength of the winds coming into it from the east, which ramped up vorticity in the northern part of the wave. Notice though that it hasn't strengthened a whole lot since last night, and it is only now beginning to move into the area where the global models had it starting to deepen in earnest.

Yea thanks
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1116. aquak9
Blue- so next saturday, either I'm gonna be hunkered down, or I'm gonna be at the beach looking for fossils and sharkteeth, right? I'm in Jax.
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I have a horrible feeling this will be a new Katrina. Charleston, or Savannah. Unprepared, due for a Hurricane, getting hit by a Cat 3 storm with strong storm surge, and a whole bunch of rain.
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Quoting Tazmanian:
932mb is a cat 5 lol

Depends. Earl and Igor were 927mb and 924mb and " only" reached 145 and 155, respectively. Not all of them are Cat 5s.
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Well, HWRF was suggusting Category 4 landfall on Charleston... unless Irene get her acts together now, I don't see Category 4 happening. However, track is still possible. Stay tuned, folks.
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Quoting Tazmanian:
932mb is a cat 5 lol


not quite. Solid Cat 4.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting LovetoaMuse:
Irene is right below us here on St. Maarten. From villa Ever Summer you can see the surf is up! Otherwise, rain with intermittent gusts.



Very pretty pic!
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So is Miami an unlikely target for Irene then?
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1109. Levi32
Quoting nigel20:

Why did Irene developed so rapidly?


Part of it was the strength of the winds coming into it from the east, which ramped up vorticity in the northern part of the wave. Notice though that it hasn't strengthened a whole lot since last night, and it is only now beginning to move into the area where the global models had it starting to deepen in earnest.
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Obvious MLC visible

Member Since: June 9, 2007 Posts: 4 Comments: 15946
1107. nigel20
Quoting HurricaneDean07:
Irene, Bum bum bum BUM


Looky what we got here, GFS 12Z Jose coming...

My word!
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Quoting aquak9:
Was really hoping to see a more eastward shift, Bluestorm keeps telling me to ignore it.
trackwise, it's possible. Strengthwise, ignores it.
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Quoting StormJunkie:
Now see, that center makes much more sense. Around 17.35N 63.5W per HH obs.


Holy cow! An SJ siting...what up dude??
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932mb is a cat 5 lol
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Irene is right below us here on St. Maarten. From villa Ever Summer you can see the surf is up! Otherwise, rain with intermittent gusts.

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1102. Levi32
Quoting barotropic:


What do U think of the significant east trend of the 12Z HWRF and GFS. The HWrF now has the storm barely clipping the xtreme NW bahamas at its closes point to FLorida (appx 225 miles). HWrF brings dtorm into S Carolina.


I think they are simply adjusting for where the center now is, much farther north than the models anticipated. That's all I did this morning as well with the new track.
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Irene, Bum bum bum BUM


Looky what we got here, GFS 12Z Jose coming...
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where is the high and is it building back in?
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Even if the HWRF is greatly exaggerating the strength, still a Cat 3 hitting Charleston head on people........
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Quoting InTheCone:


Yesterdays run


No, check for yourself. Yesterday the HWRF wasn't nearly far this east, it was still pointing at FL.
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1097. aquak9
Was really hoping to see a more eastward shift, Bluestorm keeps telling me to ignore it.
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At 126 hr (final image), 933 mb storm is on brink of direct hit on Charleston. I would say at 132 hr, it'll be direct hit for Charleston as 935 mb storm, but I'm throwing this into ocean even though I'm in Raleigh.
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.
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Quoting MiamiHurricanes09:
Lol, 2nd gen.

So do I :P
So, Irene's centers have been aligned?
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South Carolina gets it...bad.


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Quoting StormJunkie:


Yeah, it's been working hard to get that done all morning...Finally pulled through. Think the midlevel was north of the low level and they had some disagreement about where to meet until the past couple hours.



If it is stacked, once it cycles out the dry air, I would expect to see some intensification later tonight into tomorrow morning. System seems ready to go.
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HWRF @ 120

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1090. JGreco
My sister in Charleston is not going to be happy about this. It seems no matter where you adjust the cone now Charleston seems to be a bulls eye. Though I think its fascinating that the Gulf could avoid again any direct hit from storms with the protection of the Texas death ridge. Its forcefield is still strong in our region of the World, even here in Northwest Florida.
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And the end of the 12Z HWRF run.
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Quoting Drakoen:


Finally aligned with the mid level center.




????
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1087. Drakoen
Quoting MiamiHurricanes09:
Lol, 2nd gen.


I got the 2nd gen one a couple weeks ago. I don't think they make the 1st gen anymore.
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Very close to Charleston at 120 hr out. 933 mb. Again, people should not pay attention to this run.
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1085. nigel20
Quoting Levi32:


Actually my Google Earth Satellite overlay lied to me. It is stacked which is why the center looks so tight now. The coordinates put it right under the mid-level center.

Why did Irene developed so rapidly?
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looking at vis sat and HH recon looks like irene is moving straight W maybe even a S of due W
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Quoting Levi32:


In terms of a direct hit or passage of the center overhead, I think it's unlikely there, but you shouldn't ignore a storm that could hit the east coast of Florida, as it could easily spread the outer portion of itself over the Tampa area.


What do U think of the significant east trend of the 12Z HWRF and GFS. The HWrF now has the storm barely clipping the xtreme NW bahamas at its closes point to FLorida (appx 225 miles). HWrF brings dtorm into S Carolina.
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Quoting WeatherNerdPR:

You have an iPad? 1st or 2nd Generation?
I must ask LoL
Lol, 2nd gen.
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HWRF @ 114

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Quoting StormJunkie:


It's still 5 days out...OBX & NC will take it for us like they always do ;~) Thanks fellow Carolinians to the N.

I've always hear the running joke that all Atlantic coast storms are attracted by Frying Pan Shoals.
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Quoting WxLogic:
Track wise for HWRF I have to discounted as I don't see such a track with minimal land interaction happening... specially since Irene is having a hard time.


Agreed.
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Quoting MiamiHurricanes09:
Nope, actually the other way around. GFS shifted northwards, resulting in less interaction with Hispañola, and thus a more intense cyclone. I'm sure Drak or Levi will give you a more in-depth explanation. I'm off an iPad and typing is a hassle, lol.

You have an iPad? 1st or 2nd Generation?
I must ask LoL
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Preparing for direct hit on Charleston at 114 hr out as 933 mb storm.
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Quoting Levi32:


Actually my Google Earth Satellite overlay lied to me. It is stacked which is why the center looks so tight now. The coordinates put it right under the mid-level center.


Yeah, it's been working hard to get that done all morning...Finally pulled through. Think the midlevel was north of the low level and they had some disagreement about where to meet until the past couple hours.
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HWRF @ 108

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Center is definitely farther north.

Seems more defined now.

Member Since: June 9, 2007 Posts: 4 Comments: 15946
1073. Drakoen
Quoting Stormchaser2007:


Indeed.



Finally aligned with the mid level center.
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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.