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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1073. Drakoen
Quoting Stormchaser2007:


Indeed.



Finally aligned with the mid level center.
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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.

LOL
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Quoting Stormchaser2007:
Been working outside all day.

Does it seem more likely that Irene will impact Hispaniola and weaken significantly?
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.
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1070. ncstorm
12Z NOGAPS has landfall in NC

Link
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1069. WxLogic
Track wise for HWRF I have to discount it as I don't see such a track with minimal land interaction happening... specially since Irene is having a hard time.
Member Since: August 14, 2008 Posts: 4 Comments: 4965
1068. Levi32
Quoting cchsweatherman:


Interaction with Puerto Rico won't help that effort.


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.
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After that accomplishment of finding tighter, closer stacked circulation Recon heading to st croix(Likely one more, mission into Irene before getting grounded in St croix to wait her out)
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932 mb storm toward SC Coast between Charleston/Mrytle Beach at 108 mb. I would throw this model away in term of strength. Too extreme IMO.
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1065. wpb
gfdl 12z run should change also. it started well south the last two runs
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Quoting barotropic:
Georgia, SC......need to watch this.


It's still 5 days out...OBX & NC will take it for us like they always do ;~) Thanks fellow Carolinians to the N.
Member Since: August 17, 2005 Posts: 26 Comments: 16317
1063. JRRP
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Quoting cchsweatherman:


Interaction with Puerto Rico won't help that effort.


It won't. But if it crosses over Puerto Rico, it likely would not have to go over Hispaniola, offering it much more time to organize and intensify.
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Quoting StormJunkie:
Now see, that center makes much more sense. Around 17.35N 63.5W per HH obs.


Indeed.

Member Since: June 9, 2007 Posts: 4 Comments: 15877
newportrinative,

I'm sorry....but I'm an adult....I can do what I want to do... just hide me if you don't like my questions... I like coming to this blog and getting peoples opinions...
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1059. Levi32
Quoting coffeecrusader:
Nice job Levi. So am I safe in ignoring this storm now (I live in Tampa) based on your statement that said the Eastern Gulf is completely out of the picture? Thanks.


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.
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You can see irene's formation, 98L's rise and fall, and a pretty nice wave traversing africa, about to come off now. I'm out for about 12 hours now :( I'm betting irene will still be a 50mph storm.
Link
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Quoting Stormchaser2007:
Been working outside all day.

Does it seem more likely that Irene will impact Hispaniola and weaken significantly?


No, I think it seems less likely - more like a track grazing the northern part of the island.
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Quoting HurricaneDean07:
Yep, it appears Harvey is wanting to head into the BOC, circulation heading right in there

Whatever's left of it:
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I realize that the "science guy" in everyone wants a big storm to watch ... (always been fascinated by weather phenomena myself, as it happens). But really, it looks like Irene is going to smack right into PR and that should give it a good punch, and then it has H/DR to deal with and that probably will bring back to a wreck of TD. Maybe just some nice soaking rains for Florida then afterall!

Off Topic: Up here in Montana, the geese are already flocking south!
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Can't post image... someone really mess up the comments page... 935 mb toward Charleston, SC at 102 hr. Anyone buying this HWRF model? Way too strong IMO.
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Georgia, SC......need to watch this.
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting Levi32:
Irene should eventually become vertically stacked with her mid-level center, which is what is easily visible on satellite imagery. The weird recon winds observed earlier were evidence for this. A tighter center has shown up on the most recent pass, but still just west of the mid-level.


Interaction with Puerto Rico won't help that effort.
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Been working outside all day.

Does it seem more likely that Irene will impact Hispaniola and weaken significantly?
Member Since: June 9, 2007 Posts: 4 Comments: 15877
Quoting Levi32:


The NHC is showing a NW track because that's what the models showed. Their reaction time to model shifts is slow because they know about the wagging that they do, so thus the Day 5 forecast point is to the west of the consensus.

The models show a northwest to NNW track because of what you said, the Bermuda High building westward as the New England trough runs away.

Levi, are you watch the HH'ers? Maybe they have found that new center you said, they just did a weird loop de loop. Or they decided to head home, refuel and head back to Biloxi.
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What's happening? It went through the Hebert Box as a TS.

We all know what is supposed to happen.

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1048. ncstorm
Quoting K8eCane:
This sucks a wad. Reason? I am in the process of switching homeowner policies. I have a 9000 deductible for windstorm currently. My new policy with 2000 deductible takes effect the 30th


Wow...K8, that couldnt be the worst timing..
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Yep, it appears Harvey is wanting to head into the BOC, circulation heading right in there
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Quoting Bluestorm5:
Moving to NW again... 937 mb? I'm not buying this.


I agree, plus the HWRF has been overestimating intensity with every storm this year. Was doing the same with Emily.
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Nice job Levi. So am I safe in ignoring this storm now (I live in Tampa) based on your statement that said the Eastern Gulf is completely out of the picture? Thanks.
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1044. Bielle
Quoting spathy:
#531 & #532 Great timing.


Made me laugh.
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1043. nigel20
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Hwrf Shifts east significantly on 12Z run. Now shows major hurricane passing 225 miles to east of South florida and barely skirts xtreme NW bahamas (abacos) to their east.
Member Since: August 22, 2010 Posts: 0 Comments: 652
1041. TheMom
Quoting Ineluki:
We've reached what I like to call the Rorschach test portion of a tropical cyclone's life.

This is when the individual observer sees something that the other observer simply DOESN'T. For example, one poster sees, in a radar loop, the storm moving more north, whereas I see it moving more westerly and someone else could see it moving even WSW. Several frame loops are very bad for judging actual motion in my experience. Sometimes you're seeing the movement of storms within the system, or the expansion of the system in particular directions.

And as for the model runs, there are always things to consider in each run. The first and foremost is initialization; if that's wrong, then you might as well toss the entire model out. The second thing to consider is if the run is actually doing something that makes sense within the weather pattern forecast BY the model. The third thing to consider is that, over three days out, even the best model is saying "this is an educated guess at best." With Irene, you're dealing with a storm that is still organizing, with a possible path that could either carry it over warm waters or disruptive mountains, and depending on the strength of troughs a few days down the line for track. Don't become married to the notion that a couple of runs for the GFS means Florida is out of the clear, or that South Carolina isn't in play.

Remember always to observe the actual conditions, not a few frames on a loop. I can't count how many times the more over excitable here have thought a storm was moving in a direction it actually wasn't because of a loop. The NHC goes with general motion over several hours for a reason; these things aren't riding rails on the water out there after all.

Good luck to anyone in the path of Irene!
Nicely put
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Now see, that center makes much more sense. Around 17.35N 63.5W per HH obs.
Member Since: August 17, 2005 Posts: 26 Comments: 16317
Someone messed up the comments page...
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Quoting sullivanweather:


Bonnie went back to a hurricane cause it moved off land, losing the land's frictional component which cut a good 30% of the winds aloft reflected at the surface. So, naturally, once back over water and without that land friction winds were able to crank back up to 75 at the surface. In terms of pressure Bonnie was weakening the entire time.
We had 115 mph wind gusts here on Knotts Island. Also,there is alot of sound water and swamps with warm water to contribute,I get what point you are making though.
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I found this sat image of Irene the mean:

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1036. K8eCane
This sucks a wad. Reason? I am in the process of switching homeowner policies. I have a 9000 deductible for windstorm currently. My new policy with 2000 deductible takes effect the 30th
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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video


Thanks, Levi! This storm is bad news.
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Looks like the ONLY thing really holding Irene back is the dry air entrainment and doing quite a bit of damage at that.
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1033. Levi32
Irene should eventually become vertically stacked with her mid-level center, which is what is easily visible on satellite imagery. The weird recon winds observed earlier were evidence for this. A tighter center has shown up on the most recent pass, but still just west of the mid-level.
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Moving to NW again... 937 mb? I'm not buying this.
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1031. divdog
NHC TS points look right on the money at this point
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Quoting Levi32:


The NHC is showing a NW track because that's what the models showed. Their reaction time to model shifts is slow because they know about the wagging that they do, so thus the Day 5 forecast point is to the west of the consensus.

The models show a northwest to NNW track because of what you said, the Bermuda High building westward as the New England trough runs away.
What are the chances of a shove to the west when the high really builds back to the west??
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Quoting Levi32:


That is correct. She is struggling with dry air, as evidenced by outflow boundaries in the SW quadrant and weak convective tops.


Given this weak core and elongated circulation center, its hard to believe this will strengthen much, if at all, before impacting Puerto Rico and Hispanola.
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NW, and NE quad of Irene are her strongest, a lot of uncontaminated dropsondes found 50 Mph+
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Looking at visible I would estimate the direction of travel to be 275 maybe 280 atm. IMO, a reform N could be rather insignificant if it's corrected a few hours later by a more westward movement.
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1026. K8eCane
Quoting weathergeek5:
Levi32 has his video up:



Action:
Quote
| Ignore User


Member Since: December 25, 2005 Posts: 0 Comments: 1578






Levi...Why did you draw your pink line right into Wilmington? Damn
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1025. robj144
Everyone is talking about the track and probable intensity, but does anyone have any idea on how large it has the potential of being when it really gets going?
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Seem to be stalling... 944 mb now. Is this model too extreme all the time? 90 hr out. DON'T PANIC!

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12Z HWRF is way to the east.. Looks to be heading to SC/NC.
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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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