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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1421. angiest
Quoting Patrap:
D will be fine. They jus worn out from 2 a days here in 96F Plus.

Ingrahm looked fine,


Sept 8th is in Lambeau at least


And you get to play us *again*!
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1420. j2008
Quoting Hurricanes12:


Are you honestly that ignorant?

Please don't feed the trolls. Back to the tropics.....and lurking.
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1419. Guysgal
Quoting Grothar:
When the storm is over, do you think they will call it "Irene Dunne"

I believe they will be singing "Irene Goodnight!"
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gom- 23n 87w. do you see that? look on unenhanced check out the spin going on.
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Quoting lucreto:


It has no closed circulation the NHC is just jumping at opportunities to scare people, Franklin was the only legit system (and maybe Harvey) this entire season.

Then why did you have people evacuating in NC for Emily?
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1416. Mucinex
I'm no expert but from the floater it looks like Irene is already north of it's next forecast point.
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36 hours still showing weak TS, i think.
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39 hours out center joggin to the w-wnw
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Quoting lucreto:


It has no closed circulation the NHC is just jumping at opportunities to scare people, Franklin was the only legit system (and maybe Harvey) this entire season.


he may not be, but apparently you are
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1411. SXMFL
Quoting Grothar:


Not a bad idea to post these in different languages spoken there. I speak Creole, but do not speak any French. I do not think people would mind on the blog due to the circumstances. Someone might read it and and least give some warning. Here is a quick one for my Haitian friends. I wish futuremet was on so he could correct it. I don't use it much anymore.

Li se tan pou prepare yo pou yon tanpèt posib ki ka pote gwo van ak gwo lapli. Eseye jwenn nan tè segondè nan yon buildling ki an sekirite. Sa a tanpèt ka trè danjere. Nou pral priye pou ou.



L'onde est classée tempête par le NHC c'est donc IRENE qui traverse l'arc Antillais ce weekend. Saint Barth, Saint Martin, Guadeloupe et Martinique en vigilance météo ORANGE (pluies abondantes et rafales de vent à 100kmh) Prudence dans les zones inondables ainsi qu'aux objets emportés par le vent !!!


Waiting for irene in ST Martin, for those of who who don't speak french, the last sentence warns you "to be careful in areas that flood and objects being carried around by the wind"..... wouldn't want to get hit by a cow!
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Quoting floodzonenc:
Speaking of weathermen, Florida can have Jim Cantore.  I have Brick transferring from San Diego to NC.




I like lamp.
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Quoting gugi182:
you guys think the center of circulation will come closer to Puerto Rico than expected by the computer models established already



Yes, I do.
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Wipeout!




The Surfaris - Wipeout

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Lets see if Irene will be pumping the ridge.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1406. SXMFL
Quoting Grothar:


Not a bad idea to post these in different languages spoken there. I speak Creole, but do not speak any French. I do not think people would mind on the blog due to the circumstances. Someone might read it and and least give some warning. Here is a quick one for my Haitian friends. I wish futuremet was on so he could correct it. I don't use it much anymore.

Li se tan pou prepare yo pou yon tanpèt posib ki ka pote gwo van ak gwo lapli. Eseye jwenn nan tè segondè nan yon buildling ki an sekirite. Sa a tanpèt ka trè danjere. Nou pral priye pou ou.



L'onde est classée tempête par le NHC c'est donc IRENE qui traverse l'arc Antillais ce weekend. Saint Barth, Saint Martin, Guadeloupe et Martinique en vigilance météo ORANGE (pluies abondantes et rafales de vent à 100kmh) Prudence dans les zones inondables ainsi qu'aux objets emportés par le vent !!!


Waiting for irene in ST Martin, for those of who who don't speak french, the last sentence warns you "to be careful in areas that flood and objects being carried around by the wind"..... wouldn't want to get hit by a cow!
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Quoting Gorty:
So... what about the wave off of Africa, anyone think that could develop? I been also watching the satellites on that too along with Irene.

I have been checking it out. Models say fish or Bermuda.
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Quoting Patrap:
D will be fine. They jus worn out from 2 a days here in 96F Plus.

Ingrahm looked fine,


Sept 8th is in Lambeau at least


They gonna do jus fine this year. Highly upset about the fight situation with LSU right now though. I heard Jordan Jefferson kicked a guy in the head while he was down.
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Quoting P451:
IMO, She's ready to intensify.

Watch her swallow up her surface circulation and draw it into the convection.



This action could cause a northerly jog as a result.

She already appears to be skipping north of the forecast points.



Classic prep work for a north jog. Very intrigued to see what the recon will find in the morning.
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Quoting hunkerdown:
you know where you are going for that comment, don't you :)


LMAO!!
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Quoting HoustonTxGal:


Tis the season to be jorry, fa ra ra ra ra ra ra ra ra :o)


hehe, ok good...

Hopefully you're safe from this one Houston, though I'm sure you could use the rain... My family's in Beaumont, so they've seen Rita and Humberto. They're hoping for a few more years in the clear.

I wasn't in Beaumont for Rita, but I was there before and after... The difference was staggering... About 50% of the trees were gone! Beautiful shady neighborhood was sun-drenched afterwards.
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1399. Gorty
Guys, I will have an update on the area off the coast of Africa tomorrow. Too late to do it now.
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Quoting aquak9:

He got appointed last night by the powers that be...so we're just gonna flow with it.
Well there is no reason for him to be a jerk to me. Did he really appointed himself, or someone did?
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Quoting Grothar:


Well it was a strange storm in its direction. We thought we were safe. The only thing in those days we didn't have to power about losing power, because no body had any.

Sounds like Guyana when I first went, although not complaining because the stars really illuminate the sky when you cross the rivers at night, since there is no light pollution and good air quality... I bet you knew when a storm was coming, and didn't even need know one telling you, because you used your gut feeling, felt a calmness to the air, and saw the animals running and knew something was up.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1396. angiest
Quoting Orcasystems:


Ummm I warned you about stepping on those spiders... you ummm might get some rain?



Click to enlarge


Those western outliers are "scary."
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Quoting chsstormgirl:


Floyd didn't hit us... I think it ended up in NC somewhere... Cleared the entire southeast coast for that one, from Miami to Myrtle Beach. Ugh. I had forgotten Gaston; I think it was the same as a thunderstorm.... I do remember having a jeep and driving it through areas that flooded... Man I miss that car...


I drove up to cape romaine for Gaston wanted to be in NE quad. There was a post office on 17. I got out of my car and took in the 50-60mph winds. It was not until I drove back down 17 to Charleston that all hell broke loose trees falling down 17 water coming over the hwy. Mt pleasant and about 15-20 miles north got the worst of that storm if it had one more day over water it would have been alot worse. IOP got a 83mph gust
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dont for get it olny takes one too make it a bad year
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Quoting Patrap:
D will be fine. They jus worn out from 2 a days here in 96F Plus.

Ingrahm looked fine,


Sept 8th is in Lambeau at least



yep i hear ya .....ingram might be a goodun
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33 hours p.r's getting pummeled by heavy rains at the very least...
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1388. gugi182
you guys think the center of circulation will come closer to Puerto Rico than expected by the computer models established already
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Quoting Orcasystems: "Ummm I warned you about stepping on those spiders... you ummm might get some rain?"


If that behavior actually got results, I would have done the quickstep all over Texas, lol!
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Quoting NCHurricane2009:
\


Hmmm...some of us are seeing this thing NE loaded and taking a jog more toward the N...so why is the GFS 00Z still putting well south of PR? I wonder....


The data was input to the GFS at 8:00pm EST; IF a reformation is taking place; then it was likely not accounted for in the 00z run. We won't know much for sure until recon gets in in the morning though.
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Quoting HoustonTxGal:


Tis the season to be jorry, fa ra ra ra ra ra ra ra ra :o)
you know where you are going for that comment, don't you :)
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Quoting lucreto:
This thing is done looks terrible tonight will probably be reclassified as an open wave tomorrow.


Are you honestly that ignorant?
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Quoting gugi182:

WTH!!!! bit old ain't it
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1382. aquak9
Quoting Bluestorm5:
jeez... I didn't know I was not supposed to do it.

He got appointed last night by the powers that be...so we're just gonna flow with it.
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Quoting StormJunkie:
If indeed there has been a reform to the N near or under the convection; then the GFS and likely all the other global 00z runs will be initialized too far south.



re need the recon too comfrom
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1379. Patrap
img 2km Storm Relative IR Imagery with BD Enhancement Curve


Member Since: July 3, 2005 Posts: 414 Comments: 125422
Quoting cat5hurricane:

LOL. Yeah, don't kill it.

sorry, I killed it with facts.
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1377. Grothar
Quoting HimacaneBrees:


i remember that one sonny boy. j/k that was like 70 years before i was thought of.


Kids! hummmmmp
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Quoting Patrap:


Gonna pass through a nice patch of 80 kj/cm waters once it enters the Carib.
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1375. gugi182
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If indeed there has been a reform to the N near or under the convection; then the GFS and likely all the other global 00z runs will be initialized too far south.
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o_o

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1371. KEEPEROFTHEGATE (Mod)
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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.