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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Quoting alvarig1263:


It's doing pretty good so far.... lol


Don't quote him, he's a troll.
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Lightning in a tropical system shows stronger convection. Radar kinda shows this to us. The colder cloud tops shows storms building in the system. Lightning is an indicator of instability and when you see this, it means the system is getting stronger.
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Quoting kmanislander:


They've been up for 3 hours. Not sure how long each mission runs but 6 hours seems a little long.


They can stay longer than 3, especially since they are so close to base. Although, I'm not sure if they will be able to land in St. Croix right now.
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Quoting P451:


Yep if anything there is maybe what.. a 1/4 of an eyewall on the northern circulation side right now?



To answer that...we need to take a gander at the radar out of PR...that shows the internal structure of Irene better than anything right now...
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5168. nigel20
Hey guys

Irene is looking pretty good tonight.
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Quoting kmanislander:


They've been up for 3 hours. Not sure how long each mission runs but 6 hours seems a little long.


They can probably of longer since they are based out of the USVI.
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What people mean when they say Recon and radar don't match, its called denial!!!
Member Since: April 29, 2007 Posts: 0 Comments: 7930
re post 5143 radar now it looks like the scream mask
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Time: 01:54:30Z
Coordinates: 18.1N 65.2333W
Acft. Static Air Press: 844.6 mb (~ 24.94 inHg)
Acft. Geopotential Hgt: 1,465 meters (~ 4,806 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 113° at 60 knots (From the ESE at ~ 69.0 mph)
Air Temp: 14.2°C* (~ 57.6°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 62 knots (~ 71.3 mph)
SFMR Peak (10s) Sfc. Wind: 66 knots (~ 75.9 mph)
SFMR Rain Rate: 40 mm/hr (~ 1.57 in/hr)
(*) Denotes suspect data
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Quoting Hurricanes101:


they only got there at like 7, I though the missions went close to 6 hours, plus they did not have to go far at all, so they may stay out there until the next recon is ready to go at 2am


They've been up for 3 hours. Not sure how long each mission runs but 6 hours seems a little long.
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Quoting atmosweather:


Lightning in a tropical system usually indicates an intense and strengthening storm.
thank you for da explanation
Member Since: August 18, 2011 Posts: 0 Comments: 994
Quoting P451:


HAS BEEN SINCE 8AM MAYBE EARLIER. ITS OVER 100 MILES SOUTH OF PUERTO RICO AND HEADING DUE WEST. THIS WONT BE A PROBLEM UNTIL IT REACHES THE WESTERN CARIBBEAN. I DONT KNOW WHAT PUERTO RICO IS SO WORRIED ABOUT.


how is it 100 miles south? if PR is like 40 miles from north to south, and you can see that the eyeish feature is less than half that distance...just askin
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Raining heavily...
Member Since: July 7, 2010 Posts: 0 Comments: 5690
Quoting Grothar:
If it isn't a minimal hurricane, it is the best looking tropical storm, I've seen yet.

Same here. Never seen this good of shape from Tropical Storm (unless it's Hurricane now)
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Guys I dont think it will be a hurricane. I think it will have winds up to 70 mph. Thats it!
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Quoting MrstormX:
If I recall the (*) flag is always used during heavy rainfall, but shouldn't it be raining in a storms eyewall. Seems strange to me...
The flag is mostly used in places where the plane is moving from heavy rainfall to less heavy, or vice versa...where the rainfall rate is changing by a great deal along their track.
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Quoting lucreto:
Looks like the system will not survive Hispanola.
LOL
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Quoting atmosweather:


6 hour motion is 285...12 hour is 290.


Juding where the CDO is now and where St. Kitts is (Irene passed over St. Kitts this morning)...this has definetly been WNW...and if it continues...this center will only graze the N coast of DR instead of going deep into Hispaniola...not good news at all for Bahamas or US east coast right now...
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Quoting P451:


vary well.

:)






yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115234
5148. MZT
I think this will be upgraded to a hurricane at 11PM. It's so close to land, has fairly good presentation, is organizing by the hour.
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Quoting SirCane:
UKMET and GFDL still calling for Irene to head into the Gulf towards FL panhandle...


Can you post spagetti plots, please? The most recent...thanks.
Member Since: July 17, 2008 Posts: 0 Comments: 1242
Quoting kmanislander:
Recon will soon have to return to base. I would not expect much more from this mission. Maybe one more center pass in an hour


they only got there at like 7, I though the missions went close to 6 hours, plus they did not have to go far at all, so they may stay out there until the next recon is ready to go at 2am
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Wouldn't surprise me to see the NHC keep at it WNW or even 70 mph!just saying....., if they upgrade to hurricane 75mph with movement West would surprise the hell out of me , just been watching them too long.....
Member Since: April 29, 2007 Posts: 0 Comments: 7930
Quoting SirCane:
UKMET and GFDL still calling for Irene to head into the Gulf towards FL panhandle...



Those are 2 very good models......NHC won't move too much right until they too start to move right more.
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5143. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128632
Quoting P451:


HAS BEEN SINCE 8AM MAYBE EARLIER. ITS OVER 100 MILES SOUTH OF PUERTO RICO AND HEADING DUE WEST. THIS WONT BE A PROBLEM UNTIL IT REACHES THE WESTERN CARIBBEAN. I DONT KNOW WHAT PUERTO RICO IS SO WORRIED ABOUT.

SARCASM FLAG: DEFINITELY ON
Member Since: July 7, 2010 Posts: 0 Comments: 5690
Unless the turn around and do a quick run on the Centre... the next run could be contaminated with rock filled clouds.
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5140. Grothar
Does anyone remember the name of the storm that was approaching the east coast and the NHC and the incorrect data sets and they had to redo all their models. It had to be a while ago.
Member Since: July 17, 2009 Posts: 71 Comments: 26452
5139. KEEPEROFTHEGATE (Mod)
STORM WARNING...HURRICANE...STORM WARNING
Member Since: July 15, 2006 Posts: 173 Comments: 54320
It appears that Hurricane Hunters are now finding our first Hurricane of the Season, Irene. Poses a major threat to Florida Thursday/Friday. 11 p.m. should confirm what the vortex reading shows, 75 mph. Hurricane Irene.
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5136. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Clearwater1:
What? Does lighting mean during a ts?


Lightning in a tropical system usually indicates an intense and strengthening storm.
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Quoting TropicalWeatherGrl88:


At the rate it is going it will probably not have much interaction with Hispanola.




good
Member Since: May 21, 2006 Posts: 5091 Comments: 115234
5132. Patrap
San Juan
NEXRAD Radar
Velocity Azimuth Display Wind Profile

Member Since: July 3, 2005 Posts: 426 Comments: 128632
Recon will soon have to return to base. I would not expect much more from this mission. Maybe one more center pass in an hour
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Quoting JLPR2:
While I was on my room, my family saw lightning and you know what lightning in a TS means.
um... what does lightning means in TS? Is it bad?
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Quoting weatherman410:
Looks like GFDL has it's sites set on the Florida panhandle.
Lets not go there.
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5128. lennit
from info i have they will have it at 26.3 and 79.8 in 96 hrs moving nw to nnw.. for some reason can't post it
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5127. msphar
Fajardo 28 Kts. NE gusting 38 Kts.
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Quoting lucreto:
Looks like the system will not survive Hispanola.


At the rate it is going it will probably not have much interaction with Hispanola.
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5125. SirCane
UKMET and GFDL still calling for Irene to head into the Gulf towards FL panhandle...
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Quoting TropicalAnalystwx13:


I doubt it will be a continuous motion, will rather just a wobble. General motion of still be WNW.


6 hour motion is 285...12 hour is 290.
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Quoting NCHurricane2009:


What does it mean...intensification?
What? Does lighting mean during a ts?
My upstanding is that during a warm core storm, there is lack of ice, therefore inhibiting lighting discharge. That is why one does not see much lighting during major hurricanes. At least in near the core
Member Since: August 26, 2006 Posts: 0 Comments: 1548

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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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