Irene roars into life; may become the season's first hurricane

By: Dr. Jeff Masters , 12:03 AM GMT on August 21, 2011

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Tropical Storm Irene roared into life this evening, transitioning from a tropical wave to a 50 mph tropical storm in just a few short hours. An Air Force hurricane hunter aircraft in the storm was finishing up its mission when it suddenly came across a region with intense thunderstorms and surface winds of 50 mph. The aircraft found that a center of circulation had barely closed off on the southwest edge of this region, though the plane found almost no winds from the west around the circulation center. The 6:10pm EDT center fix found a central pressure of 1007mb, which is quite high for the observed 50 mph winds. Dry air to the north and west is slowing development, as well as moderate wind shear of 10 - 20 knots, as analyzed by the University of Wisconsin CIMSS group. Infrared satellite loops and radar out of Martinique show the storm is poorly organized, with no evidence of spiral bands. The center of Irene is expected to cross over the Caribbean island of Dominica early Sunday morning, but the heaviest thunderstorms lie to the north of the center, and will affect Guadeloupe, Antigua, and St. Kitts and Nevis.


Figure 1. Evening satellite image of Irene.

The computer models have shifted southwards since yesterday, and now take Irene south of Puerto Rico on Monday, and along the south shore of the Dominican Republic on Tuesday. On Wednesday, Irene should pass near or over southern Haiti, Eastern Cuba, and Jamaica. On Wednesday and Thursday, the models agree that a trough of low pressure will dip down over the Eastern U.S., which is likely to turn Irene to the north. The exact 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. We can expect that Irene will impact Central Cuba, the Bahamas, and the Florida Keys on Thursday, but it is uncertain whether Irene's turn to the north will take the storm into the Gulf of Mexico or not. Irene most reminds me of Tropical Storm Fay of 2008. 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.

Irene will be battling dry air and moderate wind shear of 10 - 20 knots through Sunday, and it will take the storm 1 - 3 days to build up an eyewall and intensify into a hurricane. Irene is more of a threat than Tropical Storm Emily of early August was, since Irene has closed off a center farther east than Emily did and has more time to organize before encountering Hispaniola. I don't think passage over Hispaniola will destroy Irene, since it is a fairly large storm, and is likely to be a hurricane by then. However, if Irene follows the NHC forecast, it will have an extended encounter with Hispaniola and Cuba on Tuesday through Wednesday that will probably weaken the storm below hurricane force. Keep in mind that the average error for an official 5-day forecast from NHC for a developed storm is 200 - 250 miles. Irene could easily miss Florida and move up the East Coast and hit North or South Carolina, or pass through the Florida Keys and into Gulf of Mexico, ending up who knows where. Given the uncertainties, this weekend would be a good time to go over your hurricane preparedness if you live anywhere in the Caribbean, Bahamas, or U.S. coast, since Irene could well be paying you a visit as a tropical storm or hurricane sometime in the next week.

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 northern Guatemala, Belize, and portions of Mexico's Yucatan Peninsula as the storm tracks westwards at 12 mph. Dissipation is expected Sunday 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.

An exceptionally active early part of hurricane season
It's been a strangely hyperactive season for weak storms in the Atlantic so far this year. Tropical Storm Irene is the 9th named storm this year, and its formation date of August 20 ties 2011 with 1936 as the 2nd earliest date for formation of the season's 9th storm. Only 2005 had an earlier date. The first eight storms this year have stayed below hurricane strength, making 2011 the first hurricane season since record keeping began in 1851 to have more than six consecutive tropical storms that did not reach hurricane strength. As I discussed in Friday's post, a major reason for this is the lack of vertical instability over the tropical Atlantic so far this year. We've had a large amount of dry, sinking air over the tropical Atlantic, and the usual amount of dry, dusty air from the Sahara, both helping to keep the atmosphere stable and stop this year's storms from intensifying into hurricanes. Hurricane activity typically ramps up big-time by August 20, with more than 80% of all the hurricanes and 65% of all the tropical storms occurring after that date. At our current pace, 2011 will become the second busiest Atlantic hurricane season on record, with 24 - 27 named storms. There are only 21 names in the list of names for a hurricane season, so we may have to break out the Greek alphabet again in late October this year, as occurred in 2005. Ironically, this was the last time the current set of names was used in the Atlantic, so 16 of this year's 21 names are repeats of 2005. I'm not too happy about seeing another hurricane season challenge the Hurricane Season of 2005 in any way, and let's hope we don't retire another five names this year, like occurred in 2005! With vertical instability much lower this year than in 2005, and that year having already seen one storm (Dennis) retired by this point in the season, I doubt that will happen, though.


Figure 2. The annual cycle of average hurricane frequency in the Atlantic. Historically, about 35% of all the tropical storms and 15% of all the hurricanes will have occurred by August 20.

Invest 98L near the Cape Verde Islands
A tropical wave near Cape Verde Islands off the coast of Africa, Invest 98L, is spreading heavy rains and strong gusty winds to those islands today. So far this morning, top sustained winds measured in the Cape Verde Islands were 23 mph at Mindelo. 98L has a long stretch of ocean to cross before it could affect any land areas. Approximately 70 - 80% of all tropical cyclones that pass this close to the Cape Verde Islands end up curving out to sea and not affecting any other land areas, according to Dr. Bob Hart's excellent historical probability of landfall charts. The latest set of long-range model runs go along with this idea, and I'd be surprised if 98L threatens any land areas.

Jeff Masters

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GFS Initialization:

Member Since: July 15, 2006 Posts: 17 Comments: 10244
1270. gugi182
users from this blog that are from Puerto Rico should prepare yourself tomorrow morning.

IN SPANISH:

Si algunos de los blogueros son de Puerto Rico sabran que las condiciones del tiempo se van a deteriorar al paso de la Tormenta Tropical Irene pasando su centro a unas 80 millas al sur de la isla. Se sentiran vientos de fuerza de tormenta tropical en toda la isla. daco congelo los precios para que se vayan preparandose.

HAVE A GOOD NIGHT TOMORROW IT WILL BE AN UGLY DAY. GO HOME IRENE GO AWAY!!!!!!
Member Since: Posts: Comments:
Quoting Grothar:
Anbody remember the Hurricane of 1906? That hit Miamia and Fort Lauderdale. I sure would like to reminisce with somebody about it.


Psst….Some of our grandmothers weren't even born then. ;)
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1268. Patrap
Member Since: July 3, 2005 Posts: 424 Comments: 128261
1267. angiest
Quoting MississippiWx:
00z GFS should be initializing shortly.


Wont this be the first full run since naming? GFS didnt seem to show a TS for another day or two previously. May have big changes if initialization is correct.
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Quoting HoustonTxGal:
If Irene does go to the more western track, and splits the uprights between Cuba and the Yukatan and hits the GOM as a Cat 4.. It will be a nightmare. She will hit that hot water in the gulf and explode just like Katrina did.. Been there, done that..ugh!


I keep seeing posts like this and wonder what are y'all seeing that indicates this? I am in south MS so have a vested interest.
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Link to GFS 00z models? I found it and it does show same maps y'all had been posting on NOAA.
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1264. Skyepony (Mod)
Irene has pulled together & come so far north since last night. She seems to be really moistening the environment. Looking where she's really pulling together I think she'll end up north of her current forecast points.
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My family is prepared for anything that Irene may bring here in San Juan,PR.I didn't liked that sentence of a possible hurricane watch for PR.

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1262. Grothar
Anbody remember the Hurricane of 1906? That hit Miamia and Fort Lauderdale. I sure would like to reminisce with somebody about it.
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Quoting Grothar:


Geez, I didn't write the dam thing, I just posted a model.
Lol i know im just stating it about the model.
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1260. beell
A HURRICANE WATCH COULD BE REQUIRED FOR PUERTO RICO TOMORROW IFTHERE IS A SIGNIFICANT NORTHWARD ADJUSTMENT TO THE TRACK FORECAST.

Guess it depends on your definition of "if" and "significant".

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Quoting Grothar:


Geez, I didn't write the dam thing, I just posted a model.


+1
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Quoting jonelu:
I experienced Irene in 1999...which caught us all of guard. Literally putting shutters on during horizontal rain...no a good idea BTW...Looks like Irene 2011 may pull a spinal attack of FL as a nod to her predecessor. We shall see.

lost my truck in the flooding from that one and replaced it with one i'm still driving today. if 2011 Irene comes my way, I'm getting home early and staying there. Can't afford to replace another vehicle for another Irene.
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Quoting Bluestorm5:
Fran and Floyd hit SC in late 90's. Hurricane Earl came close last year as major hurricane.
Fran and Floyd made landfall in NC. Don't forget Bertha before Fran in 1996, and then Bonnie(borderline 2/3) in 1998. We also had Isabel in 2003 as a category two hurricane.
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quick question after listening and reading quite a lot of posts over the years gennerally the stronger systems move north faster because they feel the troughs more than weaker systems...

if this is the case then why are the models that have a much stronger storm showing it moving further south and west than the models that turn the weaker system north?

other than it will intensify because of less land interaction but then as it does should it not be turned north towards the weakness??
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Quoting NCHurricane2009:


I see it now....

LOL...is it just me....or is the NHC contradicting themselves at the 11 PM discussion?....first they lean more west with their cone...yet make this statement about a further north reformation and Puerto Rico maybe needing a hurricane watch...this isn't making sense....
They didn't say they EXPECT a reform, just that it was possible. It's called hedging the bets, AKA known as CYA...
Member Since: October 25, 2005 Posts: 19 Comments: 22087
1253. Grothar
Quoting hurricanehunter27:
Thats how perfect conditions are. But i dont think it takes in account of landmasses.


Geez, I didn't write the dam thing, I just posted a model.
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1252. Patrap


Member Since: July 3, 2005 Posts: 424 Comments: 128261
Quoting Clearwater1:


I'm hooked. I've been a member here for going on 6 years. There are times I can't tear myself from the screen. My latest obsession is the damn gfs model runs. I have to stay up to at least watch the late night screening lol . . . and certainly when it looks like a decent shot at affecting my neck of the woods.
You got that right, this year especially I have been on all day and night, posting images, sharing my thoughts, and learning a lot from all others on here, and like you I have been eye- balling the GFS model.
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Quoting jonelu:
I experienced Irene in 1999...which caught us all of guard. Literally putting shutters on during horizontal rain...no a good idea BTW...Looks like Irene 2011 may pull a spinal attack of FL as a nod to her predecessor. We shall see.


I was in Hollywood Beach taking a vacation on the beach for Irene. The forecast wasn't very accurate. Miami ran busses in the morning and thousands of people were caught in the storm with no way home when they cancelled all transportation.

It wasn't very pleasant being on the beach either - I thought the waves might go right over my little hotel and flood my room. And that wasn't much of a storm.
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Quoting StormJunkie:


The 00z GFS initialized at 8:00pm EST (aka 00z); we should start getting output from that 00z initialization soon though.



Lol...Which is what I meant...
Member Since: July 15, 2006 Posts: 17 Comments: 10244
1248. gugi182
The local news from Puerto Rico said that an eye is going to form 80 miles south of the town of LAJAS,PUERTO RICO. It going to be a ruff day tomorrow. We are expecting winds gusts 45-70 MPH, 5-18 inches of rain, high waves and possibles water spouts in the coast. I will be experiencing Tropical Storm winds tomorrow night wow!!!!.
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Quoting PalmBeachWeatherBoy:


Deja vu?? not track wise exactly, but anyone remember hurricane irene of 1999, this was the first storm i can remember, i was 9 years old. (very sorry if this pic comes out too big, will remove if needed)


I remember Irene (1999), I was in the ninth grade. Here in Orlando, it was extremely muggy the day before, then frequent rain and breezy that night. The day of, it was overcast with hardly any rain, but it was very gusty (peaked at sustained 38 gust 48 here)for the whole day as it hugged the coast.
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Quoting hurricane23:


In terms of the HWRF? Way to much land interaction.


No, the westward shift in the models.
Member Since: July 15, 2006 Posts: 17 Comments: 10244
Quoting hurricane23:


In terms of the HWRF? Way to much land interaction.


Conditions are perfect after land interaction is over for rapid intensification..There is a really good chance it occurs, but then again, forecasting rapid intensification is very hard.
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Quoting Grothar:
My the storm is over, do you think they will call it "Irene Dunne"


stop it
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Quoting HoustonTxGal:
If Irene does go to the more western track, and splits the uprights between Cuba and the Yukatan and hits the GOM as a Cat 4.. It will be a nightmare. She will hit that hot water in the gulf and explode just like Katrina did.. Been there, done that..ugh!
Not Katrina it will blow up like Irene, we cold not even compair it to anything.
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Quoting MississippiWx:
00z GFS should be initializing shortly.


The 00z GFS initialized at 8:00pm EST (aka 00z); we should start getting output from that 00z initialization soon though.

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Quoting chsstormgirl:


For the record, SC hasn't been hit in the past 21 years. The East Coast hasn't been hit in the past five years... things that make you go hmm...


I just hope Irene doesn't change our east coast break...we are "overdue" though....whatever "overdue" means....

What worries me here is Irene may lean more NE in its projected path if she makes more reformation toward the convection....
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1238. Grothar
When the storm is over, do you think they will call it "Irene Dunne"
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Quoting MississippiWx:


What's your reasoning?


In terms of the HWRF? Way to much land interaction.
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Quoting CanesfanatUT:


YES! We need a poll:
Where will Cantore be stationed in the US?


Wouldn't he almost have to be down on one of the Keys?
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I don't think we should be so quick to jump onto the GFDL/UKMET/CMC west bandwagon just yet. I'd wait and see what the GFS, and more importantly the ECMWF does over the next few runs.

Frankly, I don't buy GOM until the Euro starts shifting that way.
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Quoting SXMFL:
Hey all, it's 11pm here in St. Martin, it was raining for a while but its calm now. We are on alerted orange, when do you all think we will see the worst, during the night or tomorrow, I want to enjoy a little of the storm! :)
Probably tomorrow more than tonight, though you will likely have some rain / wind tonight.
Member Since: October 25, 2005 Posts: 19 Comments: 22087
1233. scCane
Quoting chsstormgirl:


For the record, SC hasn't been hit in the past 21 years. The East Coast hasn't been hit in the past five years... things that make you go hmm...
Correction; we haven't been hit by a major hurricane in 21 years. The last hurricane to hit here was Gaston back in 2004 as a weak cat 1. That's actually pretty normal for South Carolina as far as hurricane hits go.
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1232. jonelu
Quoting PalmBeachWeatherBoy:


Deja vu?? not track wise exactly, but anyone remember hurricane irene of 1999, this was the first storm i can remember, i was 9 years old. (very sorry if this pic comes out too big, will remove if needed)
I just comment on that...she did catch us with our pants down. My Mom was driving to a Bette Midler concert and got caught in the middle of it all trying to get home once the concert got canceled.
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Quoting chsstormgirl:


For the record, SC hasn't been hit in the past 21 years. The East Coast hasn't been hit in the past five years... things that make you go hmm...
Fran and Floyd hit SC in late 90's. Hurricane Earl came close last year as major hurricane.
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If Irene does go to the more western track, and splits the uprights between Cuba and the Yukatan and hits the GOM as a Cat 4.. It will be a nightmare. She will hit that hot water in the gulf and explode just like Katrina did.. Been there, done that..ugh!
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1229. Grothar
Quoting floodzonenc:
Even more useless piece of info...  Irene was Archie's liberal neighbor in "All in the Family". 





There was also a famous play and movie, called "My Sister Irene" think it was written by Harvey,
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1228. ncstorm
Quoting MississippiWx:
00z GFS should be initializing shortly.


make sure your seat belts are buckled..this one will be a doozy..
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Quoting GTcooliebai:
Hurricane Alma 1966 came close, pretty much paralleled the coast. But yeah that's a long time ago. 2004 was a bad year for us, but could've been a lot worse had Charley not taken that early right hand turn. I'm looking at some of the latest models and it's not looking too good for us.
I was around for Donna, 1960, 10 years old at the time. Very exciting for a kid.
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00z GFS should be initializing shortly.
Member Since: July 15, 2006 Posts: 17 Comments: 10244
When do the "Me, Myself, and Irene" Jim Carrey jokes start?
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1224. GoWVU
Quoting chsstormgirl:


For the record, SC hasn't been hit in the past 21 years. The East Coast hasn't been hit in the past five years... things that make you go hmm...


I know I was here for the last big one "HUGO" and never wanna do it again!!
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Quoting P451:
GFS 18Z (moe, again, only up to 18z)



See...the GFS is already a bit off at the beginning of the loop with its central position of Irene...it needed to have start the run further NE...so I suspect that run is too far to the west with Irene by the end.....
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1222. jonelu
I experienced Irene in 1999...which caught us all of guard. Literally putting shutters on during horizontal rain...no a good idea BTW...Looks like Irene 2011 may pull a spinal attack of FL as a nod to her predecessor. We shall see.
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1221. ncstorm
Quoting NCHurricane2009:


I see it now....

LOL...is it just me....or is the NHC contradicting themselves at the 11 PM discussion?....first they lean more west with their cone...yet make this statement about a further north reformation and Puerto Rico maybe needing a hurricane watch...this isn't making sense....


I saw the same contradiction..not bashing the NHC of course but I think they are covering their behinds in putting in that "however"
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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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