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 NICycloneChaser:




As you can see on this radar loop, Irene is now emerging back over water. Moving WNW.
now if we can just get her going west she will slam into dominican republic and hopefully spend 12 hours there
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Quoting Relix:


The radar must be having issues. First it makes no sense because the NHC is reporting otherwise AND there are reports from Areas such as Arecibo in calm. It does make sense somewhat at the same time because Toa Alta is calling for "el virazon" so it could make sense.


I'm not sure that the NHC is really reporting it to still be over land. The last advisory said it was inland, and would continue to move over land this morning, which doesn't really give a time frame for it to be back over water. It looks to me that it may have taken a slight NW jump, which would bring it back over water much more quickly.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting TomTaylor:
got a link?


From the 4AM position update:

AT 400 AM AST...0800 UTC...THE CENTER OF TROPICAL STORM
IRENE WAS ESTIMATED BY FAA DOPPLER WEATHER RADAR TO BE
NEAR LATITUDE 18.3 NORTH...LONGITUDE 66.3 WEST...OR ABOUT
20 MILES WEST-SOUTHWEST OF SAN JUAN PUERTO RICO AND ABOUT
60 MILES EAST OF AGUADILLA PUERTO RICO.
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6720. Relix
http://www.wapa.tv/tiempo/#tab-10

Click Play. Live images of the TV Station Radar. Helpful!
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A buoy just off San Juan, PR supports the idea of the center passing back over water

Metric units



English units

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6718. Relix
http://www.wapa.tv/tiempo/

Select Doppler. There you have your COC.
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6717. Gearsts
Quoting NICycloneChaser:




As you can see on this radar loop, Irene is now emerging back over water. Moving WNW.
Link
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Quoting Relix:


Nope. NHC reporting its moving west over the north side of PR. Maybe the north part of the COC is overwater (unlikely) but the system is still inland. Land reports from users also help sustain this.
got a link?
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Quoting Relix:
Toa Alta is reporting also the sudden windshift (does this have a proper name? We just call it El Virazon). This leads me to believe that perhaps the North side of the COC is overwater. Or I just don't know. =P!


No you are correct, she is about 20 miles due W of San Juan a little E of Dorado.
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Quoting NICycloneChaser:




As you can see on this radar loop, Irene is now emerging back over water. Moving WNW.



People will still say its over land and going to be over land the whole way across
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6713. Relix
Quoting NICycloneChaser:


Irene is now emerging back over water. Moving WNW.


The radar must be having issues. First it makes no sense because the NHC is reporting otherwise AND there are reports from Areas such as Arecibo in calm. It does make sense somewhat at the same time because Toa Alta is calling for "el virazon" so it could make sense.
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Wow really? Talking dirty? WOW that doesn't belong on here with the potential that Irene has to be a monster. That needs to stop. This is purely meteorology talk.

Irene has the potential to be bigger and badder than Hugo for several reasons:

1.) if Irene were to miss any more land interaction which at this point I think is a tremendous likelihood than she can intensify rapidly up until landfall, say except for a potential EWRC. Hugo was a category four at landfall, Irene could be a category five and could be a further southwest landfall in which part could have a much greater impact on Charleston, SC.
2.) Oceanic and atmospheric conditions present are at the most ideal for a catastrophic hurricane. Upper level anticyclone present, well aligned mlc and llcs, oceanic temperatures above 84f and at great depths as well as little to any dry air, however the dry air is currently to the west and northwest, Irene is moistening her environment and is isolating her Core.

3.) biggest detriment is the restriction of appreciable convection in the southern semicircle outside of her inner core and this needs to develop to help ventilate her inner convection. Northern outflow channel is not restricted and this is helping her maintain her current organization and intensity, I give this process of developing a southern outflow channel about 12 to 24 hours to occur. If not she could end up like Hurricane Earl intensity wise and just miss category five intensity.

4.) presence of the atlantic gulf stream current will allow rapid intensification to continue to occur if an EWRC is not going to happen. This will catch a lot of residents of guard.

5.) complacency and a higher volume of residents now living in coastal SC compared to when hugo hit could increase the number of people who are potentially in harm's way, this includes my cousins, aunt and uncle as well as myself. My relatives live in Blufton, SC and I am currently in Sumter, SC.
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6711. Gearsts
Quoting Relix:


Yeah it decided to visit our north beaches :P
Jeanne had a similar track i think.
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Quoting Relix:


Nope. NHC reporting its moving west over the north side of PR. Maybe the north part of the COC is overwater (unlikely) but the system is still inland. Land reports from users also help sustain this.




As you can see on this radar loop, Irene is now emerging back over water. Moving WNW.
Member Since: August 10, 2010 Posts: 2 Comments: 1971


see the dry air coming into your eye?
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Quoting HurricaneHunterJoe:
looks like she will go east coast to west coast over land,


COC is about to or is just now emerging around San Juan into the atlantic
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6707. Relix
Quoting Gearsts:
from what i can see on radar, center is still over land moving west towards Arecibo.


Yeah it decided to visit our north beaches :P
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6706. Relix
Toa Alta is reporting also the sudden windshift (does this have a proper name? We just call it El Virazon). This leads me to believe that perhaps the North side of the COC is overwater. Or I just don't know. =P!
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6705. Gearsts
From what i can see on radar, center is still over land moving west towards Arecibo.
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6704. Relix
Rio Piedras/Guaynabo reporting the East Side. Arecibo reporting calm. Toa Baja still in calm.
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Courtesy Jonathan Vigh
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Quoting FrankZapper:
Hey Little Einstein, come down out of those clouds.


Ha ha, I probably should -- internet access is sporadic at best when you're all the way up here. And thanks for the complement (it was a complement, right?). Now to work my way to little Feynman...


Quoting TropicalWeatherGrl88:
I would say skirting would not have much of an effect. It may cause it to stop strenghtening, but I dont see how it would really hurt it too bad.


Right. In a brief burst of curiosity, I was just wondering if in certain circumstances, the terrain could aid in lifting moist flow from offshore into the circulation, which might mitigate the fact that flow from the onshore direction is cut off (and probably dry).
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6701. Relix
Quoting TomTaylor:
After spending a little more than 2 hours over Puerto Rico, Irene is already back over the warm tropical Atlantic


Nope. NHC reporting its moving west over the north side of PR. Maybe the north part of the COC is overwater (unlikely) but the system is still inland. Land reports from users also help sustain this.
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993 mb reported at Luis Munoz Marin Int'l Airport this hour...she definitely has not lost much strength if at all.

Watch the buoy just N of San Juan too, excellent observation point just E of the center. 991 mb pressure at the most recent report.
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But maybe that is just an illusion.
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6698. Relix
Bayamon reporting the east side. Its coming to get me soon!
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Quoting cycleranger:


6z Surface Winds Analysis.

Holding her own.
looks like she will go east coast to west coast over land,
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2011AUG22 061500 3.8 989.8/ +0.0 / 61.0 3.8 4.0 5.8 0.5T/hour OFF OFF -19.76 -64.26 EYE 24 IR 18.51 66.07 COMBO
2011AUG22 064500 3.8 989.9/ +0.1 / 61.0 3.8 4.1 5.7 0.5T/hour OFF OFF -12.06 -62.69 EYE 26 IR 18.55 66.30 COMBO
2011AUG22 071500 3.9 988.7/ +0.3 / 63.0 3.9 4.1 5.4 0.5T/hour OFF OFF -11.76 -60.28 EYE 29 IR 18.59 66.53 COMBO

Scene Type goes from UNIFRM to EYE...not sure what this means though. lol.
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Quoting OracleDeAtlantis:
Stop talking dirty ...


haha
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After spending a little more than 2 hours over Puerto Rico, Irene is already back over the warm tropical Atlantic




The core and surface/mid level circulations have been affected by the land interaction, however, a strong surface circulation under the mid level circulation, still remains present according to radar observations. It will take a bit for Irene to reorganize herself over the next day after crossing PR, however, once again Irene remains to the north/right of her projected path. Here's an image of the 6z consensus models with Irene's current position shown by the thumbtack.






Should the forecasted shape of Irene's track not change (which it really hasn't over the past few days - it's only shifted east), then Irene should actually miss Hispaniola all together. It still may briefly skirt the northern part of the island tomorrow, however, that part of the island is not very mountainous and I don't expect Irene to be significantly disrupted by this. Once again, the upper level environment and ocean environment are prime for intensification, so if you live on the Bahamas, SE US, or mid-Atlantic states, start preparing now. For now, Hispaniola and PR will have to watch for torrential rains.
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http://www.atmos.washington.edu/~ovens/loops/wxloop .cgi?wv_east_enhanced+12

In the end of this loop she looks more like a hurricane then ever.
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Quoting thedawnawakening3:


This means that her coc is tightening again and the convection in the northern semi circle is really intense.


Which also means she'll have plenty of moisture to try and wrap around her center when you moves out over the water.
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Quoting thedawnawakening3:


This means that her coc is tightening again and the convection in the northern semi circle is really intense.
Stop talking dirty ...
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6690. Relix
Arecibo in calm as well
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Quoting yonzabam:


How could Irene be a lot more intense than Hugo? Hugo was a cat 4 from the Antilles to landfall in S. Carolina, briefly reaching cat 5 status out at sea.



If it made landfall at the exact same strength as hugo did but 40 miles south of Charleston then it would be much worse.
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sheesh this forum is flying fast, have to refresh every 10 seconds haha and its 4 am.
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Quoting thedawnawakening3:
Dry air appears to be impacting mainly the western side of her COC, which tells me this is taking the biggest beating from dry air and land interaction.
yup
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6686. Relix
Hatillo is now reporting calm
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Quoting atmosweather:
Here you go:

AT 400 AM AST...0800 UTC...THE CENTER OF TROPICAL STORM
IRENE WAS ESTIMATED BY FAA DOPPLER WEATHER RADAR TO BE
NEAR LATITUDE 18.3 NORTH...LONGITUDE 66.3 WEST...OR ABOUT
20 MILES WEST-SOUTHWEST OF SAN JUAN PUERTO RICO AND ABOUT
60 MILES EAST OF AGUADILLA PUERTO RICO.


Since it was at 18.3N 66.1W an hour ago, it has been moving due west for the past hour with no northerly component.
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Quoting yesterway:


How is it that you are able to be online?


laptop computer and broadband internet
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Quoting atmosweather:
Here you go:

AT 400 AM AST...0800 UTC...THE CENTER OF TROPICAL STORM
IRENE WAS ESTIMATED BY FAA DOPPLER WEATHER RADAR TO BE
NEAR LATITUDE 18.3 NORTH...LONGITUDE 66.3 WEST...OR ABOUT
20 MILES WEST-SOUTHWEST OF SAN JUAN PUERTO RICO AND ABOUT
60 MILES EAST OF AGUADILLA PUERTO RICO.


This means that her coc is tightening again and the convection in the northern semi circle is really intense.
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The 6z early cycle models are more clustered taking a general track just east of FL up into SC
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Quoting Relix:


Perfect! Thank you This is why I am reporting. I am gonna take a bet and say its gonna escape through the Dorado/Manati/Vega Baja area in north PR. Right now still calm but widespread reports of "el virazon" (east side) are appearing all over social networks. Seems its very bad.


Yes I'd agree with that exit point, she is about 10 miles SE of there right now.

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6z Surface Winds Analysis.

Holding her own.
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Wow - Irene is still located over the Island traveling along route 22 west.
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Quoting 7544:


just north of pr in the water look

Link
looks like dry air coming a channel from the north,see the little dark line?
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Dry air appears to be impacting mainly the western side of her COC, which tells me this is taking the biggest beating from dry air and land interaction.
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Here you go:

AT 400 AM AST...0800 UTC...THE CENTER OF TROPICAL STORM
IRENE WAS ESTIMATED BY FAA DOPPLER WEATHER RADAR TO BE
NEAR LATITUDE 18.3 NORTH...LONGITUDE 66.3 WEST...OR ABOUT
20 MILES WEST-SOUTHWEST OF SAN JUAN PUERTO RICO AND ABOUT
60 MILES EAST OF AGUADILLA PUERTO RICO.
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Quoting QPhysFTW:


First of all, if the circulation is strong enough, it WOULD be completely disastrous if it were completely over populated land. But that aside, what I meant was disastrous in the context of maintaining a circulation, as I was in physics discussion mode. A poor choice of words, I'll admit.

And thanks to all (particulary dawnawakening) that have been so helpful in providing detailed information regarding land interaction, particularly in the context of what Irene is doing this very moment. Keep it up!
Hey Little Einstein, come down out of those clouds.
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6674. Relix
Quoting atmosweather:


Santurice gives the true location, watch the windshift from NNE to SE, meaning the storm is coming up from the SE and moving to its SW and W. It cannot possibly be over water. Also it is pretty calm and the pressure is 992 mb.


Perfect! Thank you This is why I am reporting. I am gonna take a bet and say its gonna escape through the Dorado/Manati/Vega Baja area in north PR. Right now still calm but widespread reports of "el virazon" (east side) are appearing all over social networks. Seems its very bad.
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Quoting 7544:


just north of pr in the water look

Link


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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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