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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moving north , moving south, moving east, moving west. Its north of the track, wait its now south of the track. Its gonna hit the mountains, wait, no its not. The nhc track is goofy, wait, nah it looks pretty good. When r the models gonna run again. Its gonna hit south florida, wait maybe it will hit south florida. will it pump the ridge or wont it. I love this place what a great source of cheap entertainment.
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I keep seeing all this "hype" about major storm in the Bahamas on this run, etc, etc. I only want to remind pple here that well, this run is practically identical to runs that were seen repeatedly 4-5 days ago. Yesterday P451 mentioned 3 possible options, with good accompanying graphics, and this was one of them. I'm also pretty sure the NHC cone includes this option, and that it has since the storm was initiated. Let's not act "shocked" by what has been an obvious possibility from the get-go. It's a bit too disingenuous.
Member Since: October 25, 2005 Posts: 19 Comments: 22101
Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video


Thank you very much! Ominous news.
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Quoting barotropic:


12ZHWRF still running...Keeps Irene on N coast of DR and never goes near north coast of cuba goes directly into SE bahamas....seems like big shift east coming on this run.


Agree.
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919. Skyepony (Mod)
Looking at the average model error for Irene so far... Some of these models have been in the race longer than others. TVCN & HWRF is showing some skill..

Average Position Error (in nautical miles)

Model Name 0hr 24hr 48hr 72hr
AEMN 50.7 100.3 81.1 67.8
AVNO 50.9 133.2 79.6 70.1
BAMD - 135.8 237.2 253.8
BAMM - 121.8 187.6 158.8
BAMS - 113.8 159.3 129.4
CMC 59.3 - - -
GFDL 17.5 - - -
GFDN 12.3 - - -
HWRF 12.1 75.9 127.2 -
LBAR 0 118.8 226.5 364.0
LGEM 0 112.1 187.6 158.8
MRFO 52.0 83.2 80.0 -
NAM 32.2 - - -
NGPS 64.1 69.0 63.5
TVCN 0 61.6 90.2 -
XTRP 0 132.5 305.0 623.5
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Quoting presslord:


great graphic,,,thanks

press, at the top you can change it to wave height, period swell, etc.
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Dont forget... GFS had this started around 14N and 63W.. its already 3dg further N
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THANK YOU LEVI!
glad your here, now the actual forecasting can begin(And the questions)
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Quoting Drakoen:


Out of the 2z suite so far yes.


12ZHWRF still running...Keeps Irene on N coast of DR and never goes near north coast of cuba goes directly into SE bahamas....seems like big shift east coming on this run.
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When she becomes more symmetric, could should she grow to be quite a large storm? It looks like she has that capability and is trying to grow larger.
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Quoting leftlink:


I am thinking it will be closest to the path of Tropical Storm Chris (Link) -- however the intensity when it approaches the mainland is anybody's guess.

Chris dissipated on the day i was born... ha! So I'm 23 very soon, where does the time go?

Ironically, Irene formed around the same time too and looks very similar to the image on wikipedia of Chris.
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Quoting cchsweatherman:
Just in looking at satellite imagery, Tropical Storm Irene seems to be struggling some as the circulation seems to not be very well defined and the core has been struggling to establish itself. This is evident by the widespread below normal pressure readings in the region displaced from the mean wind center. I don't see any significant strengthening for at least the next 12 hours.


Yep...that is what I gather too...I think we can call it strengthening until a great convective burst goes off in the center of that broad comma head of clouds...
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910. JRRP
Quoting cchsweatherman:
Tropical Storm Irene appears to be resuming a more westward course as indicated by the past few Hurricane Hunter fixes.

+1
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Quoting UPRM1CIMA:
Thank you, Taz.




your welcome
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Pretty strong surface trough coming down from Canada. Double barreled front! We may not even see the storm go near Florida if it gets picked up quick enough.

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Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video
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Thank you, Taz.

Quoting Tazmanian:
whats not forget that PR is a part is the USA
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Quoting AussieStorm:
Villa IntimaSea - St. John, USVI, Saint John Island

beautiful!
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Quoting NCHurricane2009:


Using that same radar image...I see the broad center moving into the SE corner of Puerto Rico....
Agree, most likely will cross the island of PR from the SE to NW, towards NE Dominican Republic.
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HH on an inbound leg again
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Quoting aquak9:
gust loop

Link


great graphic,,,thanks
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Quoting WeatherNerdPR:
BEHOLD
Irene's Center
that is some really poor resolution...
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting AllStar17:


That scenario appears to be becoming a little more likely. Is that 2 models now that indicate that?


Out of the 2z suite so far yes.
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TROPICAL STORM 09L
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 21 AUG 2011 Time : 154500 UTC
Lat : 17:02:44 N Lon : 63:23:55 W


CI# /Pressure/ Vmax
3.1 / 999.1mb/ 47.0kt


Final T# Adj T# Raw T#
2.8 3.2 3.3

Center Temp : -53.2C Cloud Region Temp : -43.9C

Scene Type : CURVED BAND with 0.67 ARC in LT GRAY

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.5T/hour
Weakening Flag : ON
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 105km
- Environmental MSLP : 1012mb
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Quoting overwash12:
Depends on the environment,we had Bonnie in 1998 intensify back to a hurricane while right on the coast of N.E. North Carolina,That was quite a surprise! Dennis upwelled the waters off the coast ,so when Floyd slowed, it did not have the heat content to feed off of.


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.
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I think the models picked up on the northerly movement over the past 12 hours. But over the past few hours, Irene has resumed a more Westerly movement.
If this continues, we could see a slight shift back to the West later today or tonight.

It will be very interesting to see Irene's movement during the day and tonight. The center of Irene will most likely move right along the South Coast of P.R.
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Quoting FLdewey:
PR Emergency Management says no school, no college, and government will be closed tomorrow.


Thats good to hear, people can concentrate on preparing for the storm
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Quoting Drakoen:
HWRF 12z shows very little interaction with Hispaniola keeping it just to the north.


That scenario appears to be becoming a little more likely. Is that 2 models now that indicate that?
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893. wpb
does anyone have the flying schedule for noaa gulfstream jet. that data will help give the models more consistency....
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Any thoughts on when, or if, the dry air entrainment will subside?
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We have to realize though with Irene avoiding most of Hispanoila and only mainly impacting NE DR, and PR. could sadly see a stronger system, with it only temporarily over land for about 36 hours intead of Several days that was forecasted yesturday
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Quoting sullivanweather:


Yup. And once Earl moved from 30-36°N, where it passed over the Gulf Stream off the coast of North Carolina, it went from Cat4 down to strong Cat1 because it ingested dry air from the continent and got swept up into the westerlies. But this storm was on the move. I was referring to the stalled storm scenario.


Oh..okay...gotcha...
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Just in looking at satellite imagery, Tropical Storm Irene seems to be struggling some as the circulation seems to not be very well defined and the core has been struggling to establish itself. This is evident by the widespread below normal pressure readings in the region displaced from the mean wind center. I don't see any significant strengthening for at least the next 12 hours.
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gust loop

Link
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Word of advice to everyone..watch the 3 day cone...the only fairly reliable cone IMHO....watch for trolls and alarmists....they are everywhere on here...No one in their right mind wants a hurricane of any way shape or form. Most of us in Florida remember 2004, and 2005. Don't want to go through that again!
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is stalled Irene?...barely moving on radar...
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HWRF 12z shows very little interaction with Hispaniola keeping it just to the north.
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Quoting KEEPEROFTHEGATE:



That's not much of a trough to lift her out.
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Quoting WeatherNerdPR:
BEHOLD
Irene's Center


Kind of fuzzy...but is that a bit of a green ring right at the center?
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HWRF 12z - 36 hrs....

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Quoting aasmith26:


F5.....F5.....F5....lol



What browser are you using? There is an auto page refresh for chrome and IE
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Villa IntimaSea - St. John, USVI, Saint John Island



St Croix Live Harbour Cam.

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whats not forget that PR is a part is the USA
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Recon. heading in for another center fix.
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Quoting NCHurricane2009:


You have a point here....only rarely does it help to strengthen a storm....like last year's Earl...which went to cat. 4 off the SE US because it wasn't in an unfavorable atmosphere like these others you cited...


Yup. And once Earl moved from 30-36°N, where it passed over the Gulf Stream off the coast of North Carolina, it went from Cat4 down to strong Cat1 because it ingested dry air from the continent and got swept up into the westerlies. But this storm was on the move. I was referring to the stalled storm scenario.
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Is that a 41MPH gust i'm seeing in St Croix?
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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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