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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Good morning from West Palm Beach, FL. Starting to appear that we'll be experiencing Irene's first U.S. landfall. Guess it's time to fill the propane tank . . .
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I think once Irene passes/skirts Hispaniola, we should have a better view as to where she is heading... IMO
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Quoting BenBIogger:
A direct hit for SFL seems unlikely at the moment.

JMO
too early to tel,l SFL to NC should pay attention.
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Quoting charlottefl:



I think barring any major shifts of the models again, this will be very close to the E Coast, assuming it clears Hispanola to the N...



Based on what I see, data feeding into models doesn't suggest a big shift back over the West Coast of Florida anytime soon, that high over Texas was underestimated again early on, the high over Texas is wanting to hold strong. So, as of now, I don't see how Irene will head any further west than the NHC center point right now unless the trough comes down weaker than expected, or unless the ridge in the Atlantic strengthens and squeezes the path of least resistance farther west.
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6869. oakland
Quoting Hurricanes12:


9-1-0

It counts as both a tropical storm and a hurricane.


You are correct.
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A direct hit for SFL seems unlikely at the moment.

JMO
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Quoting StarnzMet:
06Z GFS rolling.



It initializes Irene a tad south of PR
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I got up to read the 5am discussion. Heh
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Well Irene is now back over water. Maybe not officially, but according to radar imagery, she definitely is and has been for some time now. The resulting track has allowed Irene to spend less time over land than expected and will also push her east/right of previous forecasts. This will allow Irene to either just graze the Dominican Republic coast line, or possibly even miss it altogether. Irene will need to work on her lopsided convection and beat up core, but beyond that minimal land interaction and a very conducive upper level and oceanic environment will allow her to continue to strengthen. A major hurricane is looking quite likely at the moment. South East and Mid Atlantic states need to start preparing now, as well as the Bahamas and the Dominican Republic.

anyway, enough bad news

Quoting odinslightning:
quaddafi has fled and there are parties in the streets of Tripoli.
that's great news!

And with that I'm off to bed.
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6863. breald
It looks like Jville is right smack dab in the bulls eye for a hurricane.
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06Z GFS rolling.
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Quoting TomTaylor:
yea interesting stuff. Not sure how significant of an effect this will have on steering, but given the large ulac and resulting outflow over Irene it makes sense that this would have an effect worth mentioning in the discussion.


The GFS especially keeps forecasting the overhead ULH to expand further which would really make such a scenario a little more plausible. It hasn't happened very often but considering the uncertainty in the exact timing of the upper trough and the storm's large size it's worth considering for sure.
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Quoting Hurricanes12:
So does this pattern look better or worse for a Florida based landfall? Models trended a tad bit west last night and now then they trended back to the east. Very confusing. Lol.


Not a lot has changed in that regard. What was mentioned in the 5AM discussion is that the storm's own outflow could actually prevent the subtropical ridge from being eroded as much as the E-ern models are suggesting. That isn't specifically likely but it is something that has been seen before, whereby a strong storm actually stays on a more W-ward track rather than poleward. Hurrcane Georges in 1998 managed to do this.
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cant wait to go out to folly in 2-3 days to see the surf oh wait we might not have folly beach if this thing hits close beach erosion is gonna be a huge problem regardless
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Quoting bigwes6844:
8-1-0


9-1-0

It counts as both a tropical storm and a hurricane.
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I follow the blog all the time but I don't know enough to post much. However...since I'm up early I thought maybe I could be the first to claim Irene is annular....

(Just Kidding)
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Quoting TomTaylor:
would that be pumping the ridge?

Where is storm when you need him? Lol. interesting point indeed, though
they also mentioned the high pressure not weakening. You can see the trough digging down now on wator vapor and a low moving across the northeast. If that trough moves out quick the ridge builds back in and the storm cant recurve. Looks to be a matter of timing now but a SE coast landfall looks certain. Scary storm.
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Quoting atmosweather:


Yes that would be a case of the storm's own environment creating a confluence and maintaining mid level ridging longer than the lareg scale pattern would suggest.
yea interesting stuff. Not sure how significant of an effect this will have on steering, but given the large ulac and resulting outflow over Irene it makes sense that this would have an effect worth mentioning in the discussion.
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Quoting Hurricanes12:
So does this pattern look better or worse for a Florida based landfall? Models trended a tad bit west last night and now then they trended back to the east. Very confusing. Lol.



I think barring any major shifts of the models again, this will be very close to the E Coast, assuming it clears Hispanola to the N...
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Quoting NICycloneChaser:
9-1-0
8-1-0
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Quoting Stormchaser2007:
Irene continues WNW still...

At this heading, it would have little interaction with DR.


Yep the possibility of there being no landfall at all along Hispanola is increasing.
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Morning all.

So, the tropical storm streak is ended. What a shame. Unfortunately, intensity estimates keep rising.

Seems sort of north of PR. I think it was P451 who mentioned this possibility first (and he's made a lot of good posts on Irene, kudos his way).

Btw, oil prices down further due to Libya reaching (hopefully) the conclusion. Good news for... well, everyone.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
So does this pattern look better or worse for a Florida based landfall? Models trended a tad bit west last night and now then they trended back to the east. Very confusing. Lol.
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They're using TDWR out of San Juan, the regular radar site is down..
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Quoting TomTaylor:
yea I know. I was referring to the color enhancement used to display the radar features. I usually go to wunderground for radar, over the NWS. Not just because there are more options, but the color enhancement makes it easier to identify features on the radar itself.

So I was just wondering if that could have a little something to do with it. I doubt it, but it was just a slight possibility I was considering


They do have access to many more enhancements and special radar features than we do so yes that could be the issue.
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Quoting atmosweather:


They are using the FAA Doppler radar site at San Juan which is the same one we are using I believe. I don't think they are looking at anything different than us.
yea I know. I was referring to the color enhancement used to display the radar features. I usually go to wunderground for radar, over the NWS. Not just because there are more options, but the color enhancement makes it easier to identify features on the radar itself.

So I was just wondering if that could have a little something to do with it. I doubt it, but it was just a slight possibility I was considering
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9-1-0 folks.

The blog will literally explode in the morning (for you guys... it's already 5:32 pm here).

And Irene being a hurricane caught me by surprise too.
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like i said yesterday, shes gonna ride up the whole east coast!!
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Quoting TomTaylor:
would that be pumping the ridge?

Where is storm when you need him? Lol. interesting point indeed, though


Yes that would be a case of the storm's own environment creating a confluence and maintaining mid level ridging longer than the lareg scale pattern would suggest.
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6843. WxLogic
Good Morning...
Member Since: August 14, 2008 Posts: 4 Comments: 4927
Irene continues WNW still...

At this heading, it would have little interaction with DR.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting interstatelover7165:
I woke up 30 minutes ago and the first thing I did was check the NHC. :)


Same here. :D
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Quoting wxgeek723:
The blog will go mad once everyone starts waking up and seeing this...
I woke up 30 minutes ago and the first thing I did was check the NHC. :)
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Quoting atmosweather:
WHAT IS NOTEWORTHY IS
THAT ALL OF THE GLOBAL AND REGIONAL MODELS AGREE THAT THE OUTFLOW
OF IRENE WILL CONVERGE WITH WESTERLY TO NORTHWESTERLY UPPER-LEVEL
MID-LATITUDE FLOW OVER THE MID-ATLANTIC STATES BY 96 HOURS AND
BEYOND. THIS UPPER-LEVEL MASS CONFLUENCE COULD MAINTAIN THE MID- TO
LOW-LEVEL RIDGE A LITTLE BIT STRONGER AND LONGER THAN WHAT NOGAPS
AND THE ECMWF ARE FORECASTING...WHICH WOULD IN TURN KEEP IRENE A
LITTLE CLOSER TO THE FLORIDA EAST COAST.


Very interesting point, that's not out of the realm of possibility considering the expansive outflow that Irene will likely maintain or even grow through the forecast period.
pumping the ridge? Hmm

Where is storm when you need him? Lol. interesting point indeed, though
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Quoting TomTaylor:
That makes sense I guess. I mean that's the only logical reason I could see them positioning the storm there.

yep, that radar image is quite telling...just like the rest.

I wonder what radar site the NHC uses...I would hope they don't use the ones at the NWS. Those one's are pretty poor as far as making out features on the radar.


They are using the FAA Doppler radar site at San Juan which is the same one we are using I believe. I don't think they are looking at anything different than us.
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6837. drj27
why is the panhandle still in the cone jus asking
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Quoting atmosweather:


As you said, they do this quite often. A lot of the time its because they do not want to make members of the public or emergency management officials overreact because of a situation that occurred quicker or differently than expected. I agree with you, the whole of the center is over water now, unless the radar is not picking up on the whole surface center properly for some reason (could be possible).
That makes sense I guess. I mean that's the only logical reason I could see them positioning the storm there.

Quoting Stormchaser2007:


Have to agree with you.

yep, that radar image is quite telling...just like the rest.

I wonder what radar site the NHC uses...I would hope they don't use the ones at the NWS. Those one's are pretty poor as far as making out features on the radar.
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6835. nymore
It looks like the coc is 25 miles nnw of where NHC says on their 5 am update
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Quoting Stormchaser2007:


Have to agree with you.



See that is about as clear as daylight, at least 15 miles offshore. Both that radar and the TDWR are showing this. So I don't really have a good answer to why the NHC put the center on the coastline without any satellite or RECON confirmation.
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Also I see Puerto Rico did nothing to slow down Irene. If the extent of the interaction with Hispaniola is the NE, relatively low elevation part, there is nothing else to slow her down until landfall.
Member Since: Posts: Comments:
WHAT IS NOTEWORTHY IS
THAT ALL OF THE GLOBAL AND REGIONAL MODELS AGREE THAT THE OUTFLOW
OF IRENE WILL CONVERGE WITH WESTERLY TO NORTHWESTERLY UPPER-LEVEL
MID-LATITUDE FLOW OVER THE MID-ATLANTIC STATES BY 96 HOURS AND
BEYOND. THIS UPPER-LEVEL MASS CONFLUENCE COULD MAINTAIN THE MID- TO
LOW-LEVEL RIDGE A LITTLE BIT STRONGER AND LONGER THAN WHAT NOGAPS
AND THE ECMWF ARE FORECASTING...WHICH WOULD IN TURN KEEP IRENE A
LITTLE CLOSER TO THE FLORIDA EAST COAST.


Very interesting point, that's not out of the realm of possibility considering the expansive outflow that Irene will likely maintain or even grow through the forecast period.
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Quoting SCwannabe:


Really...duhhh




Well thats not nice
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Quoting TomTaylor:
I will admit I was premature in calling it over water, but I am still amazed at the NHC's 5am update position. There is nothing to suggest this storm is not over water. The simple fact that they have upgraded it to a hurricane should warrant the center no longer being overland. Just another example of the NHC taking the conservative route I guess.
Based off the 5am they used radar to determine the position...maybe I just don't know how to look at a radar image then?

I suppose the NHC could be seeing something I'm not
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Quoting TomTaylor:
I will admit I was premature in calling it over water, but I am still amazed at the NHC's 5am update position. There is nothing to suggest this storm is not over water. The simple fact that they have upgraded it to a hurricane should warrant the center no longer being overland. Just another example of the NHC taking the conservative route I guess.



i think we may see some bouncing around of the eyewall like we usually see at this point when stuff gets ramped up and goes through the first eyewall replacement basically.

however that being said, the funktop, rainbow, and jsl all showed a small jump offshore of the coc....but same ol same ol bounces around until it gets well defined :)
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Quoting TomTaylor:
I will admit I was premature in calling it over water, but I am still amazed at the NHC's 5am update position. There is nothing to suggest this storm is not over water. The simple fact that they have upgraded it to a hurricane should warrant the center no longer being overland. Just another example of the NHC taking the conservative route I guess.


Have to agree with you.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
Thanks everyone for your dedication,
I've been absent for a while, but I'm back, keep all of us informed.

Trunkmonkey
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Ouch, if this track holds up, this is a horrible situation for most of th GA and SC coast, and most of the E coast of FL will endure strong weather as well. It has been too long for GA to see something like this. I pray the models keep going right.
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Quoting TomTaylor:
I will admit I was premature in calling it over water, but I am still amazed at the NHC's 5am update position. There is nothing to suggest this storm is not over water. The simple fact that they have upgraded it to a hurricane should warrant the center no longer being overland. Just another example of the NHC taking the conservative route I guess.


As you said, they do this quite often. A lot of the time its because they do not want to make members of the public or emergency management officials overreact because of a situation that occurred quicker or differently than expected. I agree with you, the whole of the center is over water now, unless the radar is not picking up on the whole surface center properly for some reason (could be possible).
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Quoting wxgeek723:
The blog will go mad once everyone starts waking up and seeing this...


+100

10-12000 comments and wishcasting from Texas to Maine..lol
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the weather channel is so full of crap on this storm....


why even watch em anymore.....nbc has completely destroyed what TWC started as in 1982.....


r.i.p. TWC
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.