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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7772. wxhatt
Quoting DaytonaBeachWatcher:
Actually it's quite amusing here. Every time we have a storm to watch people sit and stare at the radar or satellite and talk about how it is north or south of the forcast points and how the NHC is going to be wrong again. In the end the NHC is usually very close if not right on with their forcasts. I expect a small shift to the right since the TVCN has moved east however with the UKMET and GFDL still way west I wouldnt expect the move to be very far east. In the end i expect the NHC to be very close within the 3 day cone.


Thank You.

Always follow the NHC forcast...
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7770. divdog
Quoting TampaBayWX:
How is it that many expert weather scientists across many countries, combined years and years of experience, hundreds of powerful computer systems, and access to all the data from hurricane hunters, satellites, buoys, and ship vessels since the 1800's DO NOT know where the hurricane is going....

Yet people sitting online at home on their couch eating cereal in their PJ's KNOW exactly where the hurricane will make land fall?

How does that add up?

I don’t understand.
What r u trying to say
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ok, will give it a few hours to percolate.
l8r
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7768. RickWPB
Quoting CothranRoss:
So as a Wilmingtonian, would it be wise to start really warning about a possible threat here or is it too early?

Too early I'd say. But... I sure would tell folks to pay attention to what is going on.
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7767. Patrap
2km Storm Relative IR Imagery with BD Enhancement Curve


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Quoting P451:





Yup. Due West. 270.




LOL ;)
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Quoting TampaBayWX:
How is it that many expert weather scientists across many countries, combined years and years of experience, hundreds of powerful computer systems, and access to all the data from hurricane hunters, satellites, buoys, and ship vessels since the 1800's DO NOT know where the hurricane is going....

Yet people sitting online at home on their couch eating cereal in their PJ's KNOW exactly where the hurricane will make land fall?

How does that add up?

I don’t understand.


lmao
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7763. wxhatt
We definitely have a strengthing hurricane on our there...

Here is the latest dropsonde data:

Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KNHC)
Transmitted: 22nd day of the month at 14:04Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Storm Number: 09
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 4
Observation Number: 09

Part A...

Date: Near the closest hour of 14Z on the 22nd day of the month
Highest Mandatory Level For Which Wind Was Reported: 700mb
Coordinates: 19.2N 67.1W
Location: 87 miles (140 km) to the NW (309°) from San Juan, Puerto Rico (USA).
Marsden Square: 043 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
996mb (29.41 inHg) Sea Level (Surface) 25.0°C (77.0°F) 25.0°C (77.0°F) 95° (from the E) 69 knots (79 mph)
1000mb -36m (-118 ft) Other data not available.
925mb 648m (2,126 ft) 21.8°C (71.2°F) 21.7°C (71.1°F) 130° (from the SE) 81 knots (93 mph)
850mb 1,382m (4,534 ft) 18.2°C (64.8°F) 18.0°C (64.4°F) 145° (from the SE) 73 knots (84 mph)
700mb 3,031m (9,944 ft) 10.4°C (50.7°F) 10.3°C (50.5°F) 160° (from the SSE) 59 knots (68 mph)

Information About Radiosonde:
- Launch Time: 13:46Z
- About Sonde: A descending radiosonde tracked automatically by satellite navigation with no solar or infrared correction.

Remarks Section...

Dropsonde Location: Dropped in eyewall 045° (NE) from the eye center.

Splash Location: 19.23N 67.21W
Splash Time: 13:51Z

Release Location: 19.16N 67.14W
Release Time: 13:46:43Z

Splash Location: 19.23N 67.21W
Splash Time: 13:51:25Z

Mean Boundary Level Wind (mean wind in the lowest 500 geopotential meters of the sounding):
- Wind Direction: 105° (from the ESE)
- Wind Speed: 85 knots (98 mph)

Deep Layer Mean Wind (average wind over the depth of the sounding):
- Wind Direction: 135° (from the SE)
- Wind Speed: 71 knots (82 mph)
- Depth of Sounding: From 696mb to 995mb

Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 159 gpm - 9 gpm (522 geo. feet - 30 geo. feet)
- Wind Direction: 95° (from the E)
- Wind Speed: 81 knots (93 mph)

Sounding Software Version: AEV 20802

Part B: Data For Significant Levels...

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point
996mb (Surface) 25.0°C (77.0°F) 25.0°C (77.0°F)
850mb 18.2°C (64.8°F) 18.0°C (64.4°F)
748mb 14.0°C (57.2°F) 13.6°C (56.5°F)
740mb 12.0°C (53.6°F) 11.5°C (52.7°F)
710mb 11.6°C (52.9°F) 11.4°C (52.5°F)
696mb 10.0°C (50.0°F) 10.0°C (50.0°F)

Significant Wind Levels...
Level Wind Direction Wind Speed
996mb (Surface) 95° (from the E) 69 knots (79 mph)
982mb 100° (from the E) 88 knots (101 mph)
953mb 115° (from the ESE) 86 knots (99 mph)
947mb 120° (from the ESE) 92 knots (106 mph)
935mb 130° (from the SE) 78 knots (90 mph)
917mb 130° (from the SE) 83 knots (96 mph)
907mb 130° (from the SE) 78 knots (90 mph)
893mb 135° (from the SE) 82 knots (94 mph)
885mb 135° (from the SE) 81 knots (93 mph)
874mb 135° (from the SE) 73 knots (84 mph)
850mb 145° (from the SE) 73 knots (84 mph)
696mb 160° (from the SSE) 59 knots (68 mph)
The highest wind observed in the "Significant Wind Levels" section is noted in bold.
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7762. 7544
nam is running
Member Since: May 6, 2007 Posts: 0 Comments: 6618
models shifting east FL might be safe
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Actually it's quite amusing here. Every time we have a storm to watch people sit and stare at the radar or satellite and talk about how it is north or south of the forcast points and how the NHC is going to be wrong again. In the end the NHC is usually very close if not right on with their forcasts. I expect a small shift to the right since the TVCN has moved east however with the UKMET and GFDL still way west I wouldnt expect the move to be very far east. In the end i expect the NHC to be very close within the 3 day cone.
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7758. Patrap
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Irene headed into dry air.
The next few hours should be interesting.


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How is it that many expert weather scientists across many countries, combined years and years of experience, hundreds of powerful computer systems, and access to all the data from hurricane hunters, satellites, buoys, and ship vessels since the 1800's DO NOT know where the hurricane is going....

Yet people sitting online at home on their couch eating cereal in their PJ's KNOW exactly where the hurricane will make land fall?

How does that add up?

I don’t understand.
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Quoting SPLbeater:


I have close friends in Wilmington, and i think you outta wait until late Tuesday. My Opinion anyways, lol


Yeah, I'd assume if it turns out it hits Florida/Georgia people would think I was crying wolf.
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Quoting reedzone:
Once again for the fishcasters.. Irene is NOT going to recurve out to sea!


Be careful saying that, the chance of it curving out sea actually appears more likely at this point than a hit on the west coast of Florida. Look at the steering, that ridge over Texas has built eastward, if Irene becomes say a major hurricane and that trough really digs in, it could pull it northeast away from the U.S.

I'm not calling for it to miss the U.S. right now, but it is not wise to say that with out a doubt it will not happen. That a no-no in meteorology 101.
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7751. Jax82
Anyone in the cone is still in danger of Irene. Spread on a 5 day forecast can be up to 300 miles. Models are going to move east and west on every run, and the fact that 2 reliable models still show a landfall in FL means there is still a lot of uncertainty. The 11am update is not too far away, but i would assume a slight easterly shift in the tracks.
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I really think we should have some watches up in Fl, This is going to be a florida storm imo Just carnt see the trof affecting Irene as much as i first thought.
Hope yall is well
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Dropsonde Location: Dropped in eyewall 045° (NE) from the eye center (it is possible this value is in radians and that our site decoded it wrong).

Splash Location: 19.23N 67.21W
Splash Time: 13:51Z



Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 159 gpm - 9 gpm (522 geo. feet - 30 geo. feet)
- Wind Direction: 95° (from the E)
- Wind Speed: 81 knots (93 mph)



996mb (Surface) 95° (from the E) 69 knots (79 mph)
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7747. ncstorm
Quoting USAFwxguy:
The real player is the second trough, the short wave foercast to come in and weaken the ridge... that will really be the factor to help determine a CONUS hit or recurve.



Dr. Masters said the best model for predicting troughs is the ECWMF and right now its not seeing an out to sea option, in fact the NHC has this storm right at GA in its forecast points, it would have to make a hard right turn to avoid the conus
Member Since: August 19, 2006 Posts: 13 Comments: 13462
Ladies and Gentlemen, the 2011 hurricane season has now been canceled. Due to the behavior on the blog we will now take down Irene and remove the storm from the Atlantic. Please return for the 2012 season, have a nice day.
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Quoting P451:


Absolutely!

lol.



WU geography: P.R is due west of St Croix. If you keep going west you get to the Bahamas. Continue west to Bermuda.
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Also important to not focus on where the center goes since tropical storm force winds will likely be felt over 100 miles from where the storm is.

NWS advises to get your hurricane supplies June 1st, yet few people actually do. Always better to be safe than sorry. And if a hurricane never hits that season, at least you have supplies in case of a Zombie Apocalypse. ;)
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Quoting Patrap:






You are getting close to having a website here on this blog...
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Quoting kwgirl:
Good morning everyone. Alright, who wished up this storm? LOL After reading through the comments, and for all the newbies in Florida or coastal areas, this comment is for you. This is a wait and see time for us. BE PREPARED to batten down or evacuate. As much as our modern technology has helped with forcast accuracies, there is still a large margin of error. No one can say for sure where this storm is going to hit, just that it will... somewhere. I have always believed that you are a target for a storm as long as it is south of your position and it is moving northerly. But as everyone knows, the storms can turn suddenly (as in Charlie) and rapidly intensify. I thought the Keys were safe from Betsy after it had passed our latitude on the East Coast. Then it did a loop and came right down the keys. The NHC is getting better in their forcasts and they even admit there is a lot of uncertainty. Decide what you are going to do NOW if the storm is threatening your area and be prepared to implement your plan at a moments notice. Welcome to the height of the season. This storm will be the first of many I believe.
You are right,they need to find out what pushed/pulled Irene farther north than expected! How are things in Key West,I lived there in 1972 and 3,Wow where has the time gone?
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12Z NAM while not a tropical model is finally showing that ridge breaking down.
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Quoting BobinTampa:


Wow. Puerto Rico drifted a lot further south than i expected!


It didn't drift, Wishcasters put sails over the mountains and steered the island south so Irene instead of passing south made a direct landfall. I think they pulled it off. Now, if Florida whishcasters could just find a bigger sail huh!
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Quoting Patrap:






shes getting larger.
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7738. 7544
irene forcast to be a cat two that close to so fla . this could go either way imo if she bulids more on the south side thing are going to happen fast isnt a watch 48 hour notice and so fla could feel the effects on weds night into thursday with the closest shell be is 2 am firday morning they have to decide this soon as we seen with all the others storms this season they have a mind of their own and gone whre no one had expected stay tuned
Member Since: May 6, 2007 Posts: 0 Comments: 6618
Quoting CothranRoss:
So as a Wilmingtonian, would it be wise to start really warning about a possible threat here or is it too early?


I have close friends in Wilmington, and i think you outta wait until late Tuesday. My Opinion anyways, lol
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Quoting Thaale:

P541, would you really call that due W? Looks more WSW. I ask because yesterday a commenter called the motion SSW and that seemed reasonable to most.


Actually I thought it was going SSE into Brazil to be honest.
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7735. Patrap




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Good morning.

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Quoting USAFwxguy:
With a strengthening cyclone and the steering flow depicted below, it could be entirely possible to get Irene to recurve and avoid CONUS (landfall) altogether



That weakness is already beginning to impart a vector to the north of 290.

Unless the high build in quick and strong, CONUS may avoid this Irene lady.


What do the steering maps look like for tomorrow and the next day? I'm pretty sure that low lifts out pretty quick and then the High builds back in and that's why the NHC has kept FL in Irene's path.
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7729. Thaale
Quoting P451:
Last night's motion:





:p



P541, would you really call that due W? Looks more WSW. I ask because yesterday a commenter called the motion SSW and that seemed reasonable to most.
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Quoting interstatelover7165:
haS anybody found a cuban radar yet? i cant find one.


It's too far away to see it yet, but here is a site when she gets closer. http://www.insmet.cu/asp/genesis.asp?TB0=PLANTILL AS&TB1=RADARES
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Wind down from 80 t o75... but pressure now 987 mb
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Quoting P451:
Last night's motion:





:p




Wow. Puerto Rico drifted a lot further south than i expected!
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7724. kwgirl
Good morning everyone. Alright, who wished up this storm? LOL After reading through the comments, and for all the newbies in Florida or coastal areas, this comment is for you. This is a wait and see time for us. BE PREPARED to batten down or evacuate. As much as our modern technology has helped with forcast accuracies, there is still a large margin of error. No one can say for sure where this storm is going to hit, just that it will... somewhere. I have always believed that you are a target for a storm as long as it is south of your position and it is moving northerly. But as everyone knows, the storms can turn suddenly (as in Charlie) and rapidly intensify. I thought the Keys were safe from Betsy after it had passed our latitude on the East Coast. Then it did a loop and came right down the keys. The NHC is getting better in their forcasts and they even admit there is a lot of uncertainty. Decide what you are going to do NOW if the storm is threatening your area and be prepared to implement your plan at a moments notice. Welcome to the height of the season. This storm will be the first of many I believe.
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Quoting BobinTampa:


them's fightin' words!


What a strange thing to say...
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About JeffMasters

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