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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1371. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 163 Comments: 52217
Quoting ncstorm:





I dont like the Nogaps for ciclogenesys but is pretty good with respect of track.. I do belive tha Irene will be close to what Nogaps predicted in the last run.
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27 hours out with a nw jog towards p.r
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jeez... I didn't know I was not supposed to do it.
Member Since: August 1, 2011 Posts: 23 Comments: 7453
1366. Gorty
Link

Watching this next... should be interesting to see if anything will develop out of it in the coming days.
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1365. Mucinex
Quoting wakd3Xn04:

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.

I also lost a car. Hence the reason I refuse to forgive Max Mayfield for not putting up the Hurricane Warning till after Irene had passed the county line. Car was pretty water tight though. I pushed it 1 1/4 miles which wasn't that hard because it was floating soo well.
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Quoting angiest:


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.


I think so too, and they may be to the north.
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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....


Just because the convection is NE of the center doesn't mean the center is going to hit PR. It's fairly common for tropical systems to be heavily weighted on their NE sides, especially when they are developing.
Member Since: July 15, 2006 Posts: 17 Comments: 10156
1362. ncstorm
Quoting floodzonenc:
Yeah... he stabbed another met with a trident.  No wonder he's not returning my calls...



LOL..great movie
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Quoting iahishome:


But if a Japanese band did cover it... ok, nevermind. It's not funny when you have to explain it. ;)

Here's hoping the GFDL doesn't come true... Seems to ram Jamaica on its way to 'the channel.'


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


Jeff Masters is actually a scientist...


"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 Florida, since (it) could well be paying you a visit as a tropical storm or hurricane sometime in the next week," hurricane expert Jeff Masters of private forecaster Weather Underground wrote in his blog on Saturday.
LinkMSNBC.com Weather
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thats why we have the recon


that will help pin point the center and where it really is
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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.



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



Click to enlarge
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Quoting jrweatherman:
Are we going to have 5 people post every 6 hrs of the GFS up to 384 hours?? Let's take a chill pill please!!!!!

well im the only1 who's supposed to be posting it but other people..
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any other scary model???

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Quoting iahishome:


But if a Japanese band did cover it... ok, nevermind. It's not funny when you have to explain it. ;)

Here's hoping the GFDL doesn't come true... Seems to ram Jamaica on its way to 'the channel.'


Whew. Whistled right over his head.
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Quoting Bluestorm5:
Fran and Floyd hit SC in late 90's. Hurricane Earl came close last year as major hurricane.


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...
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1353. 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
Member Since: July 3, 2005 Posts: 414 Comments: 125530
1352. gugi182
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Quoting MississippiWx:
18hrs...good distance south of PR.

\


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....
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Quoting iahishome:
I'll be quite interested in the output of those 0Z models since they should have HH Data in them...

No jokes about the Japanese cover band for Dexy's Midnight Runners?

'Come on Eireen'?

Anybody? Tap Tap Tap... is this thing on?


My thoughts verge on dirty...
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1349. Gorty
It's a mess over in the far eastern ATL, should be interesting to see if anything will try to develop out of it over the coming days.
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Are we going to have 5 people post every 6 hrs of the GFS up to 384 hours?? Let's take a chill pill please!!!!!
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1346. Grothar
Quoting GTcooliebai:
wise guy ;)


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.

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gom- 23n 87w. do you see that? look on unenhanced check out the spin going on.
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1344. gugi182
i think IRENE will tug more north than the expected track established by the NHC? i will stay up until the 2am update.
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24 hours out
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evening everyone

Quoting floodzonenc:
Speaking of weathermen, Florida can have Jim Cantore.  I have Brick transferring from San Diego to NC.


lol
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Cantore is headed to Port Fourchon, La. So Louisiana is definitely safe from this one.
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Quoting dfwstormwatch:

18 hours out ill say it again any1 want me to keep posting these?
yes, please do. . . and thanks.
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Quoting dfwstormwatch:
stop trying to make me angry...
I'll stop if you want.
Member Since: August 1, 2011 Posts: 23 Comments: 7453
Quoting AussieStorm:

1. Dexys Midnight Runners are a British pop group not Japanese.

2. They are best known for their song "Come On Eileen". Not Eireen.

Someone pull the plug on this guys mic and take it off him. LOL


But if a Japanese band did cover it... ok, nevermind. It's not funny when you have to explain it. ;)

Here's hoping the GFDL doesn't come true... Seems to ram Jamaica on its way to 'the channel.'
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Quoting Patrap:




pat, saints D need some extra time on the practice field it seems. i know it was preseason but "OUCH"
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1335. Patrap
TS IRENE Floater - Rainbow Color Infrared Loop
Member Since: July 3, 2005 Posts: 414 Comments: 125530
Quoting Grothar:
Anbody remember the Hurricane of 1906? That hit Miamia and Fort Lauderdale. I sure would like to reminisce with somebody about it.
Quoting Mucinex:
He's dying to take the lead of something. He's probably out of jail by now. Hope he's dead under a rock somewhere for what he did.

At least wsvn let's you know something is going on. Channel 6 you have to wait forever for them to finish their human interest stories.

Channel 4 is infested with Norcross clones. Which isn't bad, but kind of creepy when you consider Norcross picked them out himself.

Channel 10 is good because they do the tropics at the top of the show like channel 7. Trent reminds me of the kid that mows my lawn and I'll never forgive Max for not putting up the hurricane warning before Irene the 1st crossed the county line. But all-in-all their team is pretty good.

WSVN should not even be considered a news station. They always over hype every story they do, from local news to human interest to crime to weather...I have been in Palm Beach County for 7 years now and am fortunate to not be able to receive 7's transmission (not that the PBC's stations are any better...)
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Quoting Bluestorm5:
18 hrs.
stop trying to make me angry...
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1332. 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.
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18 hrs.
Member Since: August 1, 2011 Posts: 23 Comments: 7453
18hrs...good distance south of PR.

Member Since: July 15, 2006 Posts: 17 Comments: 10156

18 hours out ill say it again any1 want me to keep posting these?
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Quoting P451:


I would still maintain patience with the model runs.

What I get out of them now is that they are more clustered near Florida be it west coast, over land, or east coast.

What I get out of intensity is that the atmosphere is conducive for supporting an intense hurricane.

This does not mean you will get one however as we don't know enough about track, and thus land interaction, to make such a call.

This could prove to be a very tough track and intensity forecast for the NHC. Land interaction can cause course changes...which lead to more or less land interaction and thus varying intensity.

Really, it's a crapshoot right now I'd say.

Looks like after Puerto Rico most folks aren't going to get much warning time to prepare.





This is going to be a hard pill to swallow, no doubt. PR folks need to exercise extra caution, this is no Emily. Even on the track, the storm is N & East Loaded. I do believe Nward tugs will occur overnight.
Member Since: August 19, 2005 Posts: 5 Comments: 4863
1327. TheMom
Quoting CanesfanatUT:


YES! We need a poll:
Where will Cantore be stationed in the US?
Anywhere in the Atlantic far from any land would make me happy, I swear that dude is the storm magnet.
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1326. ncstorm
Quoting GTcooliebai:
I can't even see the West Coast of FL. because someone drew pink lines to cover it up.


um humm..thats a pretty good consensous there..
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Quoting Saltydogbwi1:
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??


Been wondering about that too.
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Grothar! Irene Dunne was a lady, this Irene will not be a lady tonight or many nights thereafter!
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Quoting PcolaDan:


Harvey
no, go further north. in the gap, just into the gom.
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1322. ncstorm
Quoting floodzonenc:
Speaking of weathermen, Florida can have Jim Cantore.  I have Brick transferring from San Diego to NC.




I think Brick is wanted for murder, he might be a no show
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Quoting P451:


At least I got something right. LOL.

Just thought it would take about 8 hours longer to accomplish what it did.


Yeah, it could a lot accomplished today...Was surprised myself. I personally didn't see this becoming Irene until tomorrow afternoon.
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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.