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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4222. amd
Quoting USAFwxguy:


no clue, but I like it better if it were to come in line with the rest. It is supposed to be a top performer. In fact, if you bad mouth it you can get banned. True story.


maybe it has something to do with the interaction of the Hispaniola mountains. My theory, for what it's worth, is that when it interacts with the mountains of Hispanola, a new center forms further south along a potential southern inflow channel (a la Gustav in 2008 after its landfall in Haiti)
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Quoting P451:
17.85N, 65W - Center located below. (green)






The dry feature (circled purple) that was followed on radar imagery the past 3 hours which had an apparent wsw motion was rotating around the circulation center.

The true surface circulation has continued on a WNW motion.

PR is in a bit of trouble with this one now.

Large wind field, intensifying system, hot towers exploding over the center.



Thankfully, but unfortunately for the people who live there, Puerto Rico should limit Irene's intensity for the time being.
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Massive tornado has destroyed the town of Goderich, Ontario.
">


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4219. ncstorm
Quoting presslord:


yup....and remember" mandatory doesn't mean mandatory....you're welcome to stay put....


...the Gullah people here refer to "binyahs' (those who're from here...and 'comyahs'...(those who have come from off)...

binyahs leave...comyahs stay...


it never fails but there is ALWAYS someone that stays on the beach when there is a CAT 3 or more heading their way..I remember the images from GUSTAV with the big waves hitting their sea wall and people were just standing there watching as if they had nothing else to do..and please dont get me started on the surfers..it tones down the seriousness of the storm and people watching think.."oh well, they out there so I dont need to leave" (I'm only talking about the beaches)
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About to get ugly for PR.

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Levi,

Is dry air prohibiting the West side from closing off its eye completely?

If so

Do you think it will pull the convection from the North down over the west and cut the dry air off?
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The worst thing right now for PR, is that Irene is strengthening pretty nice now, and she's coming in at night which could put things at risk much more(flash flooding), PR wich you luck, AND STAY INFORMED AT ALL TIMES
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4215. JLPR2
Quoting TropicalAnalystwx13:


See, I told you that you needed to prepare for a tropical storm :P


Yeah, got the windows open, waiting for Irene to show up. XD
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Quoting Levi32:


I noted a bit ago that she had slowed down on radar, and as I said then, I think the reason is the center trying to organize around the stronger convective bands that are developing to the east and north. That can lead to slowing.


Good evening Levi hope you're doing well! She has definitely slowed some from earlier today. Just got back from work and I see from the San Juan radar that she has about 40-50% of an eyewall complete, RECON finding plenty of 60-65 mph winds too. I'd say a Category 1 hurricane is becoming likely by the time she reaches the SE-ern coast of PR. Do you agree?
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Does anybody know if Irene's going N or S of Hispiaonla?
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4212. HCW
Radar with model data reload for updates

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Quoting tornadolarkin:

Dude buckle up for this storm!

I'm ready. We barely prepared for Jeanne, and we got no structural damage. I doubt it'll be any different with Irene.
P.S. I didn't mean to offend you Irene, so don't get ticked off and destroy the island.
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Quoting Torgen:


I think you should go ahead and bake those muffins, then ship them over here to Tampa for safekeeping. You're gonna be up watching the blog anyhow! :D


god u made me munchy grr and im already holed up for irene >:@
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Models coming back west a tad, TVCN slightly west.

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Quoting Bretts9112:

is that new or is that old?
thats old looks like to me
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4206. scott39
I think after Irene had the N center relocation early this morning, the models had no choice but to shift E. the NHC KNOWS that anything can change, especially out after 3 days. Thats why thier not out in the SE Atlantic with the middle track yet. Thats why the cone is in the Eastern GOM and in the SE Atlantic. They leave that room for a very good reason....Mother Nature
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4204. snotly
mountains inhibiting convection to the west
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4203. JRRP
definitivamente looks like hurricane..
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Quoting ProgressivePulse:
Weather is going to start going downhill quickly in PR.It already is
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4201. Levi32
Quoting FISHHEAD4UFl:
Can someone answer me please lol..... why is nhc shooting through florida still when most models are east of florida


They tend to avoid flinging their long-term track in the direction of a sudden model swing, in case the models just flip back the other way. They may also have a reason or two for staying west of the models. If the 0z models stay east of Florida, chances are their track will shift farther east, closer in line with them.
Member Since: November 24, 2005 Posts: 635 Comments: 26701
Quoting tropicfreak:


Noticed that you just joined, welcome to WU.


It's the three-lettered person who loves to come back, JSYK.
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Quoting JrWeathermanFL:
Post 4010. I was one of the folks that excpected a TS in the BOC.


Yes, I recall that. Well played, sir!
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4198. Thrawst
Is the northward bias of most forecasts by the models still valid? Or do they actually have a good grasp of the trough over Jersey?
Member Since: July 18, 2010 Posts: 50 Comments: 1909
Quoting FISHHEAD4UFl:
Can someone answer me please lol..... why is nhc shooting through florida still when most models are east of florida



NHC won't flop around as quickly as the models do.
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Haven't the models depicted this trough to move out rather quickly? It doesn't look like it is going to keep diving directly south. When you watch the WV loop it looks like it is already starting to level out, let alone moving extremely fast. By the looks of it, this trough will be gone before we know it. Pay attention to Michigan in particular, it is retreating. I'm no expert and this is just my own opinion. But I recall stating last night that Irene was an imminent threat to PR and would have trouble avoiding a direct hit with the island. That's not even taking into account what the effects of a direct hit would cause...weakening, decoupling, reorganizing in a different area? Idk, JMO.

Edit: Didn't the models trending East also say that Irene would be a hurricane south of DR?
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4195. Torgen
Quoting aquak9:
Hush up, scooster. Gonna be a sorry sad shame if I lose power and lose 13 lbs of frozen blueberries.

Irene will go east of me. WAY east. I hope.


I think you should go ahead and bake those muffins, then ship them over here to Tampa for safekeeping. You're gonna be up watching the blog anyhow! :D
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Quoting MiamiHurricanes09:
994.9mb.

000400 1751N 06504W 8434 01452 9949 +199 +180 006015 016 018 001 00


I am estimating that the central pressure was already 992mb a couple of hours ago. Why?

The Salt River Bay station in the northern part of St. Croix just released its 6pm to 7pm data a few minutes ago. It was down but just came back online. see data here: Link

They recorded a wind shift at 6:24pm with calm winds, but pressure continued to drop to a low of 994.91mb (29.38in), at 6:48pm as the COC moved away and intensified.

So if the storm was moving at ~14mph and it moved for 24 minutes, then 994.91 was the pressure about 6 miles from the center...

So the center pressure at 6:48pm could be 2 or 3mb lower. I am basing that on the fact that the station 6 miles in the opposite direction, Christiansted Harbor, had a 3mb higher pressure at 6:48pm (998mb).
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Quoting FISHHEAD4UFl:
Can someone answer me please lol..... why is nhc shooting through florida still when most models are east of florida


bro, that's a little far out still honestly

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Quoting JLPR2:
NHC has Irene at 17.8N.
PR starts at 17.9N, landfall seems inevitable.


See, I told you that you needed to prepare for a tropical storm :P
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4190. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129904
Quoting TStormSC:


They'd have to evacuate everything east of Charlotte.


yup....and remember" mandatory doesn't mean mandatory....you're welcome to stay put....


...the Gullah people here refer to "binyahs' (those who're from here...and 'comyahs'...(those who have come from off)...

binyahs leave...comyahs stay...
Member Since: August 13, 2007 Posts: 0 Comments: 10492
Can someone answer me please lol..... why is nhc shooting through florida still when most models are east of florida
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repost

Does everyone know how most of Irene's TS winds were to the North of her? well think again, recon finding TS winds to the south of the Center now, and you know all the large amount of Convection expanded to the North and East? its dissipating into Outflow and New Convection firing near the core, Irene is getting her self together... my Last question is WHO THE HELL TICKED HER OFF?!?
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4186. bappit
Quoting Patrap:
TS IRENE Building a SOlid core slowly but confidently tonight in Warm SST's and low Shear.


Confidently?
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Quoting iamtheman99:

yes


Irene's coming to pay a visit to Florida? I mean she in the Hebert Box,throw away the rest of the forecasting tools.
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4184. JLPR2
NHC has Irene at 17.8N.
PR starts at 17.9N, landfall seems inevitable.
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I just came back in... looks like Tropical Storm Irene is poised to hit Puerto Rico dead on: Prepare for Hurricane!

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Quoting chrisdscane:
dont new models come out at 8 anyone got thoose



SFWMD still hasn't updated Irene yet, others have though, coming soon.
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Quoting zparkie:
Thats funny , no birds here in south florida, must be knowing something we dont, my cat is acting funny too, keeps looking outside at the sky.


it's hungry
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.
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4176. Levi32
Quoting CaneAddict:


How would a sudden slow down affect the future track in your eyes?


Some slowing is expected as the ridge breaks down to the northwest. Hurricanes don't just go racing around the edges of ridges, just as cars don't fly around turns as fast as straight lanes. The short-term forward speed would have to persist for several hours to be a significant slowing.
Member Since: November 24, 2005 Posts: 635 Comments: 26701
dont new models come out at 8 anyone got thoose
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Quoting zparkie:
Charleston? that would mean the NHC would be about 800 miles off, I dont think they make that big of mistakes.


They specifically say that 5 days out the error can be off by 700-750 miles either way.

And it's not a "mistake" on their part. It's that things can and do change.
Member Since: June 1, 2007 Posts: 0 Comments: 888
Quoting HCW:
Thoughts on the latest model runs ?

The main difference is what happens towards the end of the runs...some recurve to the N and some straighten out or curve slightly back to the NW. Depends on how fast the trough pulls out and how fast the high builds in.
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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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