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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Right when the models were starting to be consistent a day or 2 ago, now they cant seem to make up their mind, well, resume the waiting game.
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Quoting traumaboyy:
Hopes and prayers for our friends in PR!!! Hope they have a safe night!!


Thanks, looks like it's not a big strike, for the moment.... Just called my sister in Ponce (SW of the eye) and they are still waiting for the rain and the wind... Don't know if anyone here in Ponce can asure that......

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6421. 7544
anyone seen the gfdl or can post worth a check tia
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6420. NCSCguy
Quoting Levi32:
0z GFDL:

Is it just me or did the GFDL move further east?
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Quoting Seawall:
This storm is hitting PR at wind speeds of over 140 mph? Is that what you guys are saying? Am I reading this wrong?


You're reading it wrong, that is a model depiction of Irene as she nears SC for landfall over open waters, over PR right now she is at 70mph.
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Quoting Bluestorm5:
um... HWRF model are for 500 mb level, not surface.

Not true, that is SLP. Sea Level Pressure.
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6417. msphar
Its over for me, with the wind dropping off in Vieques and Fajardo I am ready to crash and call it a night. I hope you all fare as well as I think my boat did, a few waves and a bit of wind and then a relaxing rest of the night. I won't get out to the boat for a few weeks. I hope nothing else comes along in the meantime.
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6416. emguy
Quoting Levi32:


The central hills of PR are only 1500 feet high, and the island is small enough that it usually is no more than a speed-bump for storms. Irene shouldn't weaken significantly, but given that her core is still fragile, she probably won't strengthen until she's moving away from the island again. Of course, Hispaniola may be waiting right there afterwards.


Levi, you touched on it, and I'm gonna finish it as people are commenting on it. Correct me if you think I am incorrect. Everyone is talking about the Puerto Rico shortcut over land, you mentioned wobbles around islands. Folks, the east side of the circulation is largely over water with winds out of the south. The western side is over land with slowing northerly winds due to friction. Mean time, those southerly winds turn to easterlies over water north of the island. It an effect of angular momentum. The jog northwest over land would not surprise, but a return to WNW once back over water north of Puerto Rico should be expected. In fact, when it clears the coaast, some might say it's moving west, it's moving west due to the faster wind speeds on the north side of the storm at that time...
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GFDL:

Member Since: July 15, 2006 Posts: 17 Comments: 10244
Radar shows banding becoming more organized and intensifying.
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6413. Levi32
0z GFDL:

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Quoting hurricane23:
00z GFDL into SFL..Strong cane


It's slowing shifting east each run... probably be in the bahamas and stay east of 79W by the 12z run.
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6411. Levi32
Quoting Bluestorm5:
IMO, since Irene is moving NW over PR; longer she's travels that direction, the more likely it'll miss Hispaniola.


Correct, but we'll have to see. Often NW wobbles around an island mass like this are short-lived. Obviously any kind of northward jumps right now are bad news for those hoping Irene will weaken over Hispaniola.
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Quoting Bluestorm5:
IMO, since Irene is moving NW over PR; longer she's travels that direction, the more likely it'll miss Hispaniola.


Eye looks to be traveling to the west of El Yunque in PR headed towards an exit near Canovanas
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Quoting thedawnawakening3:


I know if that was at the surface, but 900mb is not at the surface, likely 1000-2000 feet above the surface. 1000mb is the surface. Therefore a 10-20% reduction would give an estimate of 155-165mph winds.
sigh, I've never heard any hurricanes going that strong near East Coast since Andrew.
Member Since: August 1, 2011 Posts: 28 Comments: 8007
Irene is a easy storm to forecast..hardest part is the near term of her moving more WNW with NW wobbles staying east of the initial model runs.

Nothing has changed in the future track as the models have a short term westward bias due to weak initialization of the system and too much ridging to the north of Irene. She will bend more W but still this is a Bahamas-Carolinas system. Chance of this making a "Landfall" in florida south of Daytona is around 10% right now
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Quoting Stormchaser2007:
Irene might exit in NE PR...


Looks more like in the Dorado or Arecibo area...
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Hopes and prayers for our friends in PR!!! Hope they have a safe night!!
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00z GFDL into SFL..Strong cane
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6404. Seawall
.
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A Irene made landfall her circulation has begun to fill in some, but her spiral bands are becoming more intense and are organizing more and wrapping around her center more. I don't think PR will do much to stop her intensification, maybe temporarily impede strengthening, but not overall weaken her, also her large circulation will do anything it can to minimize the impacts land will have on her circulation. I think Irene will miss Hispaniola to the northeast as well.
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Quoting 7544:
time for the eruo will it agree with gfs or the cmc ? place yourbets now
texas........lol
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Member Since: June 9, 2007 Posts: 4 Comments: 15889
Quoting 1million:


Nice radar... but will be over land for a long time


Not according to radar. It's on a NW heading and moving at a fairly fast pace. It will be offshore in a couple of hours at the most.
Member Since: July 15, 2006 Posts: 17 Comments: 10244
Quoting Levi32:


The central hills of PR are only 1500 feet high, and the island is small enough that it usually is no more than a speed-bump for storms. Irene shouldn't weaken significantly, but given that her core is still fragile, she probably won't strengthen until she's moving away from the island again. Of course, Hispaniola may be waiting right there afterwards.


But won't the way she is moving north cause her to be north of Hispaniola, or just graze it at best?
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Quoting Bluestorm5:
thanks... still high end Category 4 for Charleston. Another Hugo?


Remains to be seen...I'm still not convinced that Florida won't receive the direct hit.
Member Since: July 15, 2006 Posts: 17 Comments: 10244
Quoting Levi32:


The central hills of PR are only 1500 feet high, and the island is small enough that it usually is no more than a speed-bump for storms. Irene shouldn't weaken significantly, but given that her core is still fragile, she probably won't strengthen until she's moving away from the island again. Of course, Hispaniola may be waiting right there afterwards.
IMO, since Irene is moving NW over PR; longer she's travels that direction, the more likely it'll miss Hispaniola.
Member Since: August 1, 2011 Posts: 28 Comments: 8007
Center sure has not relocated.
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Quoting MississippiWx:


Good find. It appears that they are going to keep giving position updates while she's over or near land.


They always give 1 hr position updates while an area is under a hurricane warning.
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Quoting ProgressivePulse:



Well, currently Irene is in the NE Caribbean Sea. Once Irene goes N of the islands she'll be in the Western Atlantic.....To be specific :-/



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I still think Irene is a hurricane. Anyway, not much weakening is occurring at the moment.

Member Since: July 15, 2006 Posts: 17 Comments: 10244
Quoting MississippiWx:


No, those winds are off the surface. Would probably be around 150mph.
thanks... still high end Category 4 for Charleston. Another Hugo?
Member Since: August 1, 2011 Posts: 28 Comments: 8007
Levi any reason to think this NW motion might continue? And, do you think the storm is actually headed NW... or did the center possibly relocate N once again?
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Quoting Bluestorm5:
just posted that 154 knots = 178 MPH


I know if that was at the surface, but 900mb is not at the surface, likely 1000-2000 feet above the surface. 1000mb is the surface. Therefore a 10-20% reduction would give an estimate of 155-165mph winds.
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Quoting MississippiWx:
She's not going to stay over PR very long. She's pushing off Puerto Rico...



Nice radar... but will be over land for a long time
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Based on what you guys are seeing might the models keep shifting back and forth or is it getting pretty solidified toward the east?
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Winds have been from the N all night;

Soon they will turn from the S

The electricity is yelling.... Will be gone soon... So goodnite..

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PR REALLY getting blown up on...WOW, this storm is putting on a bit of a show...
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Quoting bayoubrotha:
TROPICAL STORM IRENE TROPICAL CYCLONE POSITION ESTIMATE
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
200 AM AST MON AUG 22 2011
New position

estimate
AT 200 AM AST...0600 UTC...THE CENTER OF TROPICAL STORM IRENE
WAS ESTIMATED BY FAA DOPPLER RADAR AND RECONNAISSANCE AIRCRAFT
TO BE NEAR LATITUDE 18.2 NORTH...LONGITUDE 65.9 WEST...OR ABOUT
15 MILES SOUTH-SOUTHEAST OF SAN JUAN PUERTO RICO.

SUMMARY OF 200 AM AST...0600 UTC...INFORMATION
------------------------------------------------- -
LOCATION...18.2N 65.9W
ABOUT 15 MI...25 KM SSE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...989 MB...29.20 INCHES

$$
FORECASTER STEWART


Good find. It appears that they are going to keep giving position updates while she's over or near land.
Member Since: July 15, 2006 Posts: 17 Comments: 10244
6383. Levi32
Quoting Bluestorm5:
okay. Guess I'll have to keep eye on it... do you think Puetro Rico will affect Irene, or it'll weaken just 5-10 mph? Sorry for annoying questions :\


The central hills of PR are only 1500 feet high, and the island is small enough that it usually is no more than a speed-bump for storms. Irene shouldn't weaken significantly, but given that her core is still fragile, she probably won't strengthen until she's moving away from the island again. Of course, Hispaniola may be waiting right there afterwards.
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Quoting Bluestorm5:
is these the strength of winds at surface? 154 knots = 178 mph?


No, those winds are off the surface. Would probably be around 150mph.
Member Since: July 15, 2006 Posts: 17 Comments: 10244
Irene might exit in NE PR...
Member Since: June 9, 2007 Posts: 4 Comments: 15889
Quoting thedawnawakening3:
Wow 00z HWRF peak intensity of 900mb 154 knot winds would likely equate to around a 165mph category five hurricane. Incredible. Irene I could see making a quick exit off of Puerto Rico heading north of Hispaniola and peak intensity of category 4/5 as she encounters warm waters and an indeal atmospheric environment for intensification.

BTW, my younger brother who's 18 has joined the NAVY ROTC program, wants to be a navy office, while I'm stationed in SC as an airman. Go figure.
just posted that 154 knots = 178 MPH
Member Since: August 1, 2011 Posts: 28 Comments: 8007
AT 200 AM AST...0600 UTC...THE CENTER OF TROPICAL STORM IRENE
WAS ESTIMATED BY FAA DOPPLER RADAR AND RECONNAISSANCE AIRCRAFT
TO BE NEAR LATITUDE 18.2 NORTH...LONGITUDE 65.9 WEST...OR ABOUT
15 MILES SOUTH-SOUTHEAST OF SAN JUAN PUERTO RICO.


11PM position was 17.9N 65.5W...therefore short term motion is closer to NW than WNW as radar has confirmed.
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Reports of more than 120K without electricity in PR with reports coming in of power transformers exploding.
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6377. msphar
Fajardo winds 31 Kts. E gusting to 53 Kts.
Esperanza winds 45 Kts. S gusting to 56 Kts.
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TROPICAL STORM IRENE TROPICAL CYCLONE POSITION ESTIMATE
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
200 AM AST MON AUG 22 2011
New position

estimate
AT 200 AM AST...0600 UTC...THE CENTER OF TROPICAL STORM IRENE
WAS ESTIMATED BY FAA DOPPLER RADAR AND RECONNAISSANCE AIRCRAFT
TO BE NEAR LATITUDE 18.2 NORTH...LONGITUDE 65.9 WEST...OR ABOUT
15 MILES SOUTH-SOUTHEAST OF SAN JUAN PUERTO RICO.

SUMMARY OF 200 AM AST...0600 UTC...INFORMATION
------------------------------------------------- -
LOCATION...18.2N 65.9W
ABOUT 15 MI...25 KM SSE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...989 MB...29.20 INCHES

$$
FORECASTER STEWART
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Wow 00z HWRF peak intensity of 900mb 154 knot winds would likely equate to around a 165mph category five hurricane. Incredible. Irene I could see making a quick exit off of Puerto Rico heading north of Hispaniola and peak intensity of category 4/5 as she encounters warm waters and an indeal atmospheric environment for intensification.

BTW, my younger brother who's 18 has joined the NAVY ROTC program, wants to be a navy office, while I'm stationed in SC as an airman. Go figure.
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That is a very healthy looking wave coming off of Africa just dipping its toes in the water.
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Quoting MississippiWx:
is these the strength of winds at surface? 154 knots = 178 mph?
Member Since: August 1, 2011 Posts: 28 Comments: 8007

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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.