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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12Z HWRF is way to the east.. Looks to be heading to SC/NC.
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Quoting winter123:
In other news... remember Lisa last year? I thought 98L might pull something like this. Now it looks unlikely. Too much sarahan dust. Is the african wave train over for the year, or what??


I was thinking more of a Julia track.
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Quoting MZT:
Very good blog update by Lev32... the fast disappearance of the weakness and the rebuilding ridge pushing on the storm late next week is not something that has been discussed much so far.

Agree with all the main points in his video.


I like Levi's work, but its far from clear where and if the storm is going...the Carolinas solution appears to be a greater possibility than yesterday, but yesterday we were talking about the center relocating well south of where it is now and toward the west.

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Time: 17:02:00Z
Coordinates: 17.3833N 63.55W
Acft. Static Air Press: 842.9 mb (~ 24.89 inHg)
Acft. Geopotential Hgt: 1,483 meters (~ 4,865 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 240° at 3 knots (From the WSW at ~ 3.4 mph)
Air Temp: 20.1°C* (~ 68.2°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 7 knots (~ 8.0 mph)
SFMR Peak (10s) Sfc. Wind: 22 knots* (~ 25.3 mph*)
SFMR Rain Rate: 0 mm/hr* (~ 0 in/hr*)
(*) Denotes suspect data

looks like this might be the new center fix
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Very obvious downdrafts coming from Irene's circulation.


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1018. Levi32
Quoting cchsweatherman:
Irene's core seems weak to me.


That is correct. She is struggling with dry air, as evidenced by outflow boundaries in the SW quadrant and weak convective tops.
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Quoting Levi32:


Oh please Press...an A- would take my GPA below 3.0...have mercy!


I'm off to go flyin'....over the Carolinas...you let me know when to pack up and leave town...and I'll count it as extra credit ;-)
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Now I can upload again. Waiting for next image... going to be ugly...
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Quoting cchsweatherman:
I'm really not seeing a WNW motion with Tropical Storm Irene as some have advertised. Based upon Hurricane Hunter fixes and satellite imagery, Irene appears to be on a due west course.


Next center fix will be near 17.3833N 63.55W as recon just found.

That is over 40 miles NNW of the last (suspect) center fix.
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HWRF for August 25 00Z: Same strength, but to the NE.
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Quoting SavannahStorm:
Recon found a MUCH tighter, closed circulation @ 17.3833N 63.55W


they just watched levis tidbit showed em where to go
LOL jk
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Is Harvey's COC moving into the Bay of Campeche?
Link
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Prepare for one helluve doomcast on the 12z HWRF for South and North Carolina (for Pressy).
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I know that Andrew came ashore on the 26th and all, but this is not Like Andrew. or is it? Andrew was headed north towards the upper us coast or even out to sea, but an area of High pressure built back and push him towards the coast. Is that a possibility here. Should Irene get into the Bahamas. Just asking anyone here who may have an opinion. I know that will be hard to find. lol
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1008. Levi32
Quoting Abacosurf:
Thanks Levi.

Brave statement to say that west Florida has been taken out of the equation.

Hope your not eating those words in a day or two....

Why is the NHC showing such a NW track through day 5.

Because the AB high is building back to the west???


The NHC is showing a NW track because that's what the models showed. Their reaction time to model shifts is slow because they know about the wagging that they do, so thus the Day 5 forecast point is to the west of the consensus.

The models show a northwest to NNW track because of what you said, the Bermuda High building westward as the New England trough runs away.
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1006. ncstorm
Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video


Thanks Levi..I think..LOL!
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Quoting connie1976:
Levi,
Do you think that at the 5 pm update that parts of south florida will be out of the cone?



Connie
I'm sorry but seems to me you are only here to try and find out the forecast for a storm since you live in FL. No one knows where this is going and your best bet is to watch your local news for the latest updates.
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1004. gugi182
my 5th storm in PUERTO RICO

1989 HUGO
1996 HORTENSE
1998 GEORGES
2004 JEANNE
2011 IRENE
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Thanks Levi,I believe the storm could be a monster once it's nearing the coast of the Carolinas. I will definitely keep a watch here in N.e. North Carolina!!!
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Recon. revealed a much tighter circulation well NW of the previous fix:
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948 mb over Grand Bahamas at 84 hr. This page is messed up, and image uploader is hidden...
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Irene's core seems weak to me.
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Yep, Recon needs to be landed by the air police and put on a breathilizer, going everywhere trying to find the center... LOL
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The new Euro out yet?
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Quoting amd:


And, yes, a new center has formed. Recon just updated, and expect the location of the new center to be around 17.367 N 63.525 W.

seems that would be accurate.
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We've reached what I like to call the Rorschach test portion of a tropical cyclone's life.

This is when the individual observer sees something that the other observer simply DOESN'T. For example, one poster sees, in a radar loop, the storm moving more north, whereas I see it moving more westerly and someone else could see it moving even WSW. Several frame loops are very bad for judging actual motion in my experience. Sometimes you're seeing the movement of storms within the system, or the expansion of the system in particular directions.

And as for the model runs, there are always things to consider in each run. The first and foremost is initialization; if that's wrong, then you might as well toss the entire model out. The second thing to consider is if the run is actually doing something that makes sense within the weather pattern forecast BY the model. The third thing to consider is that, over three days out, even the best model is saying "this is an educated guess at best." With Irene, you're dealing with a storm that is still organizing, with a possible path that could either carry it over warm waters or disruptive mountains, and depending on the strength of troughs a few days down the line for track. Don't become married to the notion that a couple of runs for the GFS means Florida is out of the clear, or that South Carolina isn't in play.

Remember always to observe the actual conditions, not a few frames on a loop. I can't count how many times the more over excitable here have thought a storm was moving in a direction it actually wasn't because of a loop. The NHC goes with general motion over several hours for a reason; these things aren't riding rails on the water out there after all.

Good luck to anyone in the path of Irene!
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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video
Thanks Levi.

Brave statement to say that west Florida has been taken out of the equation.

Hope your not eating those words in a day or two....

Why is the NHC showing such a NW track through day 5.

Because the AB high is building back to the west???
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Quoting presslord:
Levi...that was just outstanding...would be a 100...but I'm afraid I'm gonna have to clip you 5 points for the "Carolinas" reference....


Give 'em hell Paul! LOL
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Recon found a MUCH tighter, closed circulation @ 17.3833N 63.55W
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If Irene hugged the SE coast =, there could be substantial flooding as shown by the QPF.
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Quoting presslord:
Levi...that was just outstanding...would be a 100...but I'm afraid I'm gonna have to clip you 5 points for the "Carolinas" reference....


Oh please Press...an A- would take my GPA below 3.0...have mercy!
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Someone is doing the picture pasting, but if they don't paste is often, I'll do it. Waiting for 84 hr, but it won't be pretty.
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"to clip you 5 points for the "Carolinas" reference"....



Did press jus tell Levi that the Clip 5 is taking it to the Carolina's ?

Tap, Tap


Is this thing on.......?
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988. amd
Quoting keisa90:




Exactly.


And, yes, a new center has formed. Recon just updated, and expect the location of the new center to be around 17.367 N 63.525 W.
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Thanks Levi! I am really hoping for us to be out of the cone soon.. I really like my power and roof tiles!!
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Still at 9-0-0

The question is...

will we still be at 9-0-0 in 48 hours?
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HWRF @ 78 hrs, for taz!...

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Next Vortex message will be WELLLLL north of the last one...
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Warm waters ahead for sure.

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Unfortunately, and not meaning to cause alarm, Irene may be pretty well-intact if she only scrapes the northern part of Hispaniola, and if she moves towards the Carolinas instead of Florida, the amount of time allotted over water could allow a major hurricane. We will have to see. A storm into Florida would likely be weaker than that.
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Hello to everyone on the blog. member since last year but lurker since 2005. My wife & I went through 6 hurricanes in Florida from 2004 - 2005 including Jeanne & Wilma - the one thing we learned thru every storm was to stay calm and be prepared...we were newbies having lived in Mississippi all our lives until we moved. This is my first, and probably only comment, but to all those trying to predict any sort of catastrophy anywhere...don't....you may get that which you do not want. Everyone should stay prepared and hope for the best.
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Quoting Bluestorm5:
oh boy... 961 mb storm coming closer to Bamhamas at 72 hr out (3 full days from now)

pic or link?
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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Sunday, August 21st, with Video


Excellent video update. Thanks and keep up the good work!
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Quoting InTheCone:
HWRF @ 72 hrs...





there we go
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Quoting divdog:
moving north , moving south, moving east, moving west. Its north of the track, wait its now south of the track. Its gonna hit the mountains, wait, no its not. The nhc track is goofy, wait, nah it looks pretty good. When r the models gonna run again. Its gonna hit south florida, wait maybe it will hit south florida. will it pump the ridge or wont it. I love this place what a great source of cheap entertainment.


True dat. Patience.....
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LOL @ Recon trying to do a center fix, but looking like they need a DUI.
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975. MZT
Very good blog update by Lev32... the fast disappearance of the weakness and the rebuilding ridge pushing on the storm late next week is not something that has been discussed much so far.

Agree with all the main points in his video.
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Irene is a large system, so storm surge might be equivalent to say a cat 1 cane. Not sure how one would determine that though.
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Don't start freaking out... 951 mb over Bahamas
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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.