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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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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1172. 7544
hmmmm

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* SOUTHEASTERN BAHAMAS AND THE TURKS AND CAICOS ISLANDS
Member Since: May 6, 2007 Posts: 0 Comments: 6618
Quoting MiamiHurricanes09:
Damn, looks like we've been tracking the incorrect circulation.



so where would that put the center at 17N?
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Wow...hadnt seens the 12z CMC...dont put much weight on it but it to keeps the center of Irene going along N coast of DR. Irene entirely misses the NW Bahamas well off florida and skirts NC Banks and New England area. I am feeling much better about my area (SE FlA), feel bad if this becomes a problem for those to our north.
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999mb? OMG
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The center jumped...Recon found both the mid-level and low-level centers aligned, and they just found 999 mb.

Irene the terrible is strengthening.
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1166. aquak9
Quoting Bluestorm5:
Dunno... but Jax is under great threat of hurricane. Not sure as a major or low level hurricane yet. Florida to Virginia show be watching this storm carefully. Listen to what's NHC is saying.


thanks Blue. I appreciate the response.

carry on ya'll.
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still 50
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1164. SXMFL
Quoting LovetoaMuse:
Irene is right below us here on St. Maarten. From villa Ever Summer you can see the surf is up! Otherwise, rain with intermittent gusts.


Hey neighbor! Where are you on the island? We're in OB, surf isn't that bad over here, we've seen worse. Even seeing a little sun trying to poke through!
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1163. Levi32
Quoting MiamiHurricanes09:
Damn, looks like we've been tracking the incorrect circulation.


No, it just jumped under the mid-level center as of the latest recon pass. This was expected based on obs in earlier passes.
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Quoting MississippiWx:
I guess I'm making rookie mistakes... sorry, still learning the tropics. One thing I know for sure is that people in Florida to Virginia need to watch this carefully. This may be the long waited monster East Coast storm.
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Quoting P451:
Make of it what you will. Again, you cannot focus on wobbles especially that of an elongated center. Satellite imagery and center fix to center fix will NOT give you a proper heading (as many have been fixated on what appears to be a due west motion, which is not a true storm motion).

Use PR Radar, long range, long loop. Soon enough of the center will be in place for you to see what is happening.


And, this is what is happening:









We aren't worried about wobbles or absolute motion at the present time. The center has been or is in the process of relocating and that is what has caused the odd movement.
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Quoting cyclonelover1:
im just asking, I live in miami and Im just wanting to know if I shoulod get ready or not

IMO yes you should always expect the worst
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Dropspnde hit a pressure of 999mbs

No wonder they had all those weak readings.
Member Since: June 9, 2007 Posts: 4 Comments: 15718
Levi, how dare you say a major hurricane may be paying me a visit.

How dare you!

LOL!
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That 999mb is impressive; did not expect that.
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Pressure down to 999mb! Big drop in the last hour...
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1155. 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.
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1154. JGreco
Quoting midnightstorm:
I am just a bit happier seeing the GOM out of the equation!NOLA is still in dis repair! Glad we are out of the picture! though we are so very hot! and need rain!


Are friend the Texas Death Ridge is shielding us for now. May even the rest of the season. I do feel bad for all the East Coasters. All the long range models seem to make them a bullseye for more events to come.:o
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Quoting Bretts9112:

dumb comment of corse it is a likely target
im just asking, I live in miami and Im just wanting to know if I shoulod get ready or not
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Dad's checking to see if the generator works, Mom's moving all the potted plants, tables and chairs outside into the garage. I'm praying for this to dissipate XD
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Quoting Levi32:
999mb

000
URNT12 KNHC 211727
VORTEX DATA MESSAGE AL092011
A. 21/17:02:00Z
B. 17 deg 23 min N
063 deg 33 min W
C. 850 mb 1412 m
D. 43 kt
E. 251 deg 8 nm
F. 033 deg 40 kt
G. 301 deg 36 nm
H. 999 mb
I. 15 C / 1530 m
J. 21 C / 1519 m
K. NA / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 3 nm
P. AF300 0209A IRENE OB 17
MAX FL WIND 56 KT NE QUAD 15:44:20Z
MAX FL TEMP 21 C 194 / 6 NM FROM FL CNTR
;
Damn, looks like we've been tracking the incorrect circulation.
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Hey Junky...Took residence back here yesterday. Good to see ya.
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NHC adjusted to 17.5
Member Since: June 9, 2007 Posts: 4 Comments: 15718
1148. ncstorm
can someone post the link for the RI flag on?
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Quoting connie1976:
newportrinative,

I'm sorry....but I'm an adult....I can do what I want to do... just hide me if you don't like my questions... I like coming to this blog and getting peoples opinions...

very lucky you!! for a comment like that the Admon banned me for 24 hrs!!
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uh-oh

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Quoting Levi32:


In terms of a direct hit or passage of the center overhead, I think it's unlikely there, but you shouldn't ignore a storm that could hit the east coast of Florida, as it could easily spread the outer portion of itself over the Tampa area.


No Tampa, just keep chanting, No Tampa!!
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anyone got levis video?
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Quoting aquak9:
Blue- so next saturday, either I'm gonna be hunkered down, or I'm gonna be at the beach looking for fossils and sharkteeth, right? I'm in Jax.
Dunno... but Jax is under great threat of hurricane. Not sure as a major or low level hurricane yet. Florida to Virginia show be watching this storm carefully. Listen to what's NHC is saying.
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1142. ncstorm
Quoting NICycloneChaser:
WOW, Vortex messages have a drop from 1007mb to 999mb in 90 mins. Looks like Irene is about to really get going.


RI going on?
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Quoting Bluestorm5:
Well, HWRF was suggusting Category 4 landfall on Charleston... unless Irene get her acts together now, I don't see Category 4 happening. However, track is still possible. Stay tuned, folks.
A Cat 4 with the track the HWRF is showing is very possible.
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Hang tight.....by tonight its going to be much clearer where the storm is headed.
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P451, you are a person of great logic and observation.... agree with you... don't get caught up in the wobbles... take the sum average of all points and you have true direction. Radar is showing west motion (general) to me.

Quoting P451:
Make of it what you will. Again, you cannot focus on wobbles especially that of an elongated center. Satellite imagery and center fix to center fix will NOT give you a proper heading (as many have been fixated on what appears to be a due west motion, which is not a true storm motion).

Use PR Radar, long range, long loop. Soon enough of the center will be in place for you to see what is happening.


And, this is what is happening:







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1138. Levi32
999mb

000
URNT12 KNHC 211727
VORTEX DATA MESSAGE AL092011
A. 21/17:02:00Z
B. 17 deg 23 min N
063 deg 33 min W
C. 850 mb 1412 m
D. 43 kt
E. 251 deg 8 nm
F. 033 deg 40 kt
G. 301 deg 36 nm
H. 999 mb
I. 15 C / 1530 m
J. 21 C / 1519 m
K. NA / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 3 nm
P. AF300 0209A IRENE OB 17
MAX FL WIND 56 KT NE QUAD 15:44:20Z
MAX FL TEMP 21 C 194 / 6 NM FROM FL CNTR
;
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so with a llc that is not well defined,everyones completely taken the eastern gom out as a option,seems a littlè beligerant considering wevcould see a good amount t of land interaction weakening /disturbing any llc and could lead to a more westward track imo
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WOW, Vortex messages have a drop from 1007mb to 999mb in 90 mins. Looks like Irene is about to really get going.
Member Since: August 10, 2010 Posts: 2 Comments: 1970
Quoting cyclonelover1:
So is Miami an unlikely target for Irene then?

dumb comment of corse it is a likely target
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I am just a bit happier seeing the GOM out of the equation!NOLA is still in dis repair! Glad we are out of the picture! though we are so very hot! and need rain!
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Quoting CCSoFLA79:
Hello all! I enjoy reading all your posts and they are very helpful! So thank you.
My questions is. I live in Fort Lauderdale. Is this something I need to start preparing for? I have seen some chatter saying it is going up the coast. I know it is too early to tell but it just scares the bagebeez outa me.
Do early preps. [Early preps are the things that can be done without major disruption to daily life, like stocking up on non-perishables.] Listen for further info. A lot is going to depend on where this storm travels in the next 48 hours as to what you have to prepare for.

Quoting CaicosRetiredSailor:
...Still at. 9-0-0
LOL... I like the optimism of this.... can we dream??? lol

Quoting scottsvb:
NHC has Florida in the cone for now.. but it will adjust to the bahamas. Florida isnt 100% not going to be hit.. but chances are like 20% only.

I wouldnt be suprised to see this go even more East than the 12Z GFS run Long range 5day outlook showing a threat to Carolinas.. but it's too far out to say yet.
Uh... look at the cone again, dude... the Bahamas is ALREADY in the cone... sheesh...

Quoting Skyepony:
Oceansat of 98L
That looks closed... how come we never get good passes like this over the Caribbean???? lol

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1131. sngalla
2 pm is out.
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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.
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Quoting WeatherNerdPR:

Depends. Earl and Igor were 927mb and 924mb and " only" reached 145 and 155, respectively. Not all of them are Cat 5s.



so ture
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1127. WxLogic
12Z CMC US is almost completely spare.
Member Since: August 14, 2008 Posts: 4 Comments: 4881
1126. ncstorm
12Z CMC


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Quoting Cotillion:


not quite. Solid Cat 4.



oh ok
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Quoting Stormchaser2007:
Obvious MLC visible



Are those outflow boundaries in the SW part of the storm?
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1123. Walshy
Quoting Tazmanian:
932mb is a cat 5 lol


Was that suppose to make me laugh too? : /
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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.