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 Tazmanian:



so is this good news now for Hispaniola. i hop?


Well, yes and no. It is good because some parts that would have gotten winds if Irene took a more southern path will not get winds. The bad news is, they will still get A LOT of rain.
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Quoting HurricaneDean07:
but she is strengthening now...

2:00 PM AST Sun Aug 21
Location: 17.5°N 63.7°W
Max sustained: 50 mph
Moving: WNW at 18 mph
Min pressure: 999 mb

No disussion yet





the disussion will come out at 5pm
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Hi all! thanks for all the great information over the years I've been lurking. I have a question. Is there any OFFICIAL KML or KMZ files that are available that are not specifically storm related? I know the NHC site has GIS and other files but they are all storm specific. I would like to add a layer to my application that would always show the latest tracks/cones etc. Currently, I would have link to different files based on the active storms. What I am looking for is a single KML or KMZ that is updated to show current activity.

Thanks!
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Quoting Stormchaser2007:
A storm not even Cantore could weather.


Looks a wee bit annular.
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Quoting AllStar17:
999mb vortex. 8 mb drop.




Dont forget the center appeared to be over St Kitts hours ago. ANd they had a 1002 mb press at the time at 11am this morning. St Kitts is at 17.2 or 3
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Quoting Hurricanes12:
Can anyone post a pic of the new updated spaghetti model runs? The most recent ones, please.


12z models from FSU (for a bigger perspective, click here):


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O_o

999 mb pressure....the only news I see the very last few frames is she is jogging more westward than WNW right now...which increases its chances to be disrupted over the DR rather than graze the DR north coast...

...this is very fingernail biting right now...these are the critical hours that decide how Irene turns out in the end....
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Not rapid RI, but still impressive. I guess East Coast is under one huge tank gun.
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A storm not even Cantore could weather.

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but she is strengthening now...

2:00 PM AST Sun Aug 21
Location: 17.5°N 63.7°W
Max sustained: 50 mph
Moving: WNW at 18 mph
Min pressure: 999 mb

No disussion yet
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Quoting TropicalAnalystwx13:


Yep...And then the very northern part of Hispaniola.



so is this good news now for Hispaniola. i hop?
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Quoting MiamiHurricanes09:
Damn, looks like we've been tracking the incorrect circulation.
Been right on NHC track all along.
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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video


OMG...this has doomcast written all over it for me if this comes into fruition...this is very...very bad for me if this happens....
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HWRF

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1209. 900MB
Hurricane by 8pm. This is as good as it has looked. Filling in completely.
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Quoting AussieStorm:
Product: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 21st day of the month at 17:29Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 300)
Storm Number: 09
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 19

Mandatory Data...

Observation Time: Sunday, 17:26Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 17.5N 64.8W
Location: 104 miles (168 km) to the SE (127°) from San Juan, Puerto Rico (USA).
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 950 meters
Flight Level Wind: From 40° at 42 knots (From the NE at ~ 48.3 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 19°C
Flight Level Dew Point: Not available, probably because the dew point hygrometer was not working.
Weather (within 30 nautical miles): Thunderstorm(s)
925 mb Surface Altitude: 761 geopotential meters

Optional Data...

Estimated Surface Wind: From 50° at 30 knots (From the NE at ~ 34.5 mph)

Remarks Section...

Surface Wind Speed (likely by SFMR): 29 knots (~ 33.4mph)
Mission Status: Concluded (Last Report)

Thanks for the great work, safe trip home.




i oder them too go back in
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I felt like part of me just died XD
Also if you write 999 on a piece of paper and then flip 180 degrees it says 666. :O
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Well, Category 4 in Charleston = Category 1/2 in Raleigh? Uh-oh. Also, my school is one of few shelters inland NC for people that lives on coast of NC. And just in time for first day of my junior year on Thursday...
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Quoting Clearwater1:
Boy, it's moveing fast, 18 mph, per 2pm report

it actually slowed a bit if im not mistaken i think it was moving west at 22 mph this moring
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1204. Dirtleg
Does anyone have cyclone oz's live web cam site? I notice he's not on StormJunkie.com. I know he bought a ticket to florida.
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Quoting ecflweatherfan:
IDK... based on what I see from radar and satellite pics, the true location is right where the vortex message shows it to be, and I see no indication of a NNW or NW motion in the satellite or radar. Relocation of the LLC, yes, however not moving NW or NNW at this time. And deepening very quickly down to 999 mb is impressive.


well if its true that 1002mb were found a couple of hours ago, and it was a tropical storm 50mph with a depression mb of 1006-7 (that was weird enough)
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Quoting P451:


Heading right for PR.



Yep...And then the very northern part of Hispaniola.
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1201. amd
Quoting Bluestorm5:
Well, wasn't expecting 999 mb pressure. I guess that weather station in St. Kitts is right after all with 1002 mb pressure.


absolutely. Looks like I need some more crow for saying that reading was erroneous.
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Quoting HurricaneDean07:
Irene is not rapidly Intensifying, Recon was putting the center fix on the dying off Center, and didnt find the new center's pressure until just a bit ago...


The center we were tracking a while ago WAS the center, it just jumped and aligned itself with the MLC.
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Can anyone post a pic of the new updated spaghetti model runs? The most recent ones, please.
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Boy, it's moveing fast, 18 mph, per 2pm report
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It should be noted that any land interaction that disrupts Irene and weakens it will lead to a storm headed more westward and missing the trough. In other words it would be headed up the eastern gulf.
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Quoting P451:


Going right for PR. WNW.



i know bro, im finishing up on the gas stove, last minute battery and flashlights, picking up stuff, topping gas off, checking the inverter etc.

thank god its gonna be only a cat1 at the most when it gets here, folks really need to watch this one
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Quoting K8eCane:
This sucks a wad. Reason? I am in the process of switching homeowner policies. I have a 9000 deductible for windstorm currently. My new policy with 2000 deductible takes effect the 30th

I feel your pain! I live in Charleston and it looks like my insurance policy, along with everything else might be put to the test a little later on this week.
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IDK... based on what I see from radar and satellite pics, the true location is right where the vortex message shows it to be, and I see no indication of a NNW or NW motion in the satellite or radar. Relocation of the LLC, yes, however not moving NW or NNW at this time. And deepening very quickly down to 999 mb is impressive.
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Irene is not rapidly Intensifying, Recon was putting the center fix on the dying off Center, and didnt find the new center's pressure until just a bit ago...
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999mb? Maybe HWRF is right after all.........hurricane before PR? Which model predicted that.....
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1190. JLPR2
Quoting Stormchaser2007:
I hope PR is prepared.

FULL SIZE



Eh.. More or less. XD
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Quoting StormJunkie:


17.35N



so where would that put the track
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2:00 pm out.

Irene pressure down 8 mb and it has also slowed a tad.
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Product: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 21st day of the month at 17:29Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 300)
Storm Number: 09
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 19

Mandatory Data...

Observation Time: Sunday, 17:26Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 17.5N 64.8W
Location: 104 miles (168 km) to the SE (127°) from San Juan, Puerto Rico (USA).
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 950 meters
Flight Level Wind: From 40° at 42 knots (From the NE at ~ 48.3 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 19°C
Flight Level Dew Point: Not available, probably because the dew point hygrometer was not working.
Weather (within 30 nautical miles): Thunderstorm(s)
925 mb Surface Altitude: 761 geopotential meters

Optional Data...

Estimated Surface Wind: From 50° at 30 knots (From the NE at ~ 34.5 mph)

Remarks Section...

Surface Wind Speed (likely by SFMR): 29 knots (~ 33.4mph)
Mission Status: Concluded (Last Report)

Thanks for the great work, safe trip home.
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i'd bet irenes llc goes just south of pr or skirts the southern coast,look for a due westbor slight ly south of west track thru 24hrs imo
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Well, wasn't expecting 999 mb pressure. I guess that weather station in St. Kitts is right after all with 1002 mb pressure.
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i sure hop that drop from 1007mb too 999mb is not a start of a RI
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Quoting ncstorm:


RI going on?


Hard to say, but averaging a 1mb drop every 10 minutes is pretty impressive.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
999

Coordinates: 17.4N 63.5W
Location: 182 miles (294 km) to the ESE (113) from San Juan, Puerto Rico (USA).
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Quoting Tazmanian:



so where would that put the center at 17N?


17.35N
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Quoting Levi32:
The pressure drop is further evidence that Irene is now stacked and has begun the strengthening process. Next step is to get deeper convection in the core. Puerto Rico may disrupt that processes, along with some mid-level dry air, but Irene looks like she wants to strengthen.


Great...
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I hope PR is prepared.

FULL SIZE

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999mb vortex. 8 mb drop.
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1176. WxLogic
Quoting Drakoen:
Healthy shift to the east on the 12z models. Will have to see if the trend continues in future runs. The location of Irene's center favors the right side of the NHC's track.


With that new fix... most definitely.
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Quoting AussieStorm:
It's 3:30am and I'm off to bed for about 4hrs sleep. Got my son's zone athletics carnival to go to at 8am. To everyone here from PR, please please please be safe. If your unsure if your house is not able to handle High TS/Low Cat 1 winds, secure your home and evac to a shelter or to a friends or neighbours home. I will be checking in from my mobile phone during tomorrow, will try to comment. Goodnight and Stay safe.
thanks!
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Worth noting:

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* SOUTHEASTERN BAHAMAS AND THE TURKS AND CAICOS ISLANDS
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1173. Levi32
The pressure drop is further evidence that Irene is now stacked and has begun the strengthening process. Next step is to get deeper convection in the core. Puerto Rico may disrupt that processes, along with some mid-level dry air, but Irene looks like she wants to strengthen.
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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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