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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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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Quoting BahaHurican:
They didn't say they EXPECT a reform, just that it was possible. It's called hedging the bets, AKA known as CYA...



NHC are not sure of the track even the short term... They will wait to recon tommorow to make a clear statement in the forrescast. I believe that Irene will be closer to PR. It should be a crazy day tommorow as Irene approach our island.
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1319. Gorty
Quoting presslord:


Jeff Masters is actually a scientist...


Yeah but come on, that's a pretty bold statement to make so early in the season. Of course it can happen, but no one knows for sure till the end of the season.
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1318. gugi182
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1317. Grothar
Quoting 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!!!!!!


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.
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Quoting ncstorm:


I can't even see the West Coast of FL. because someone drew pink lines to cover it up.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1315. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127804
1314. Mucinex
Is the coc at 16N59w?
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1312. JLPR2
Quoting AussieStorm:

I wonder how significant a jump would have to be for it to be significant.


One latitude degree or half of it.
Member Since: September 4, 2007 Posts: 7 Comments: 8653
12 hrs.

Member Since: August 1, 2011 Posts: 28 Comments: 7981
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?

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
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12 hours out a bit of weakening...
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1307. gugi182
anybody knows if IRENE will pull a little north and come closer to PUERTO RICO anybody knows thru satellite images?
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1306. ncstorm


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Quoting HoustonTxGal:


I went thru Ike in TX , Katrina in MS and others over the years and thank you for ytour efforts to help after the storms :o)

i was there too
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1304. jonelu
Quoting snow2fire:


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.
Ya she was a cat1 and exited off of Jupiter (N Palm Beach County) so it was much stronger up here than what you got down in Hollywood...but ya...very little notice.
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Quoting Gorty:
Wow, is Dr. Masters seriously thinking we will enter the greek alphabet again? Kudos to him to venture in to an idea that goes way beyond what JB has ever thought of!


Jeff Masters is actually a scientist...
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6 hour

Member Since: August 1, 2011 Posts: 28 Comments: 7981
Quoting 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".



Beell? Your last name isn't Cleentun is it? :D J/K
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00z gfs 6 hours out
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Quoting Grothar:
Anbody remember the Hurricane of 1906? That hit Miamia and Fort Lauderdale. I sure would like to reminisce with somebody about it.
wise guy ;)
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Quoting Grothar:
Anbody remember the Hurricane of 1906? That hit Miamia and Fort Lauderdale. I sure would like to reminisce with somebody about it.


i remember that one sonny boy. j/k that was like 70 years before i was thought of.
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1297. Patrap
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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.



In fact, the 00Z intialization is a blend of observations and the trial fields (fields of tendancies) which are derived from the 18Z run. You can see, therefore, why model errors can propagate through a sequence of runs and that it is rare for models to shift their results too quickly, even in the face of data. Just a pedantic met sidetrack.
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Quoting USAFwxguy:
Iggggnition;


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Quoting 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".


I wonder how significant a jump would have to be for it to be significant.
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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?
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Quoting Skyepony:
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.


A lot of us it looks like are thinking this tonight...including myself....so I am leaning with the northern camp of the models tonight if I had to pick which models to believe right now...
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1291. gugi182
is there going to be a HURRICANE WATCH for PUERTO RICO anybody knows?
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Quoting BahaHurican:
They didn't say they EXPECT a reform, just that it was possible. It's called hedging the bets, AKA known as CYA...


Certainly looks like that may be what's going on though Baha.
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Dinner time!

Let's see what happens with the GFS...
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Quoting sarahjola:
what is that churnning by the yucatan just in the gom?


What is left of Tropical Storm Harvey.
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Quoting WPBHurricane05:


Psst….Some of our grandmothers weren't even born then. ;)
LOL
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Not gonna stick around for the 0z GFS tonight. Need a bit of a break from the constant model watching.

I'll leave you guys with my blog update.

I'll probably be back sometime tonight, though. Cheers.
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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.

exactly why I said don't buy it just yet. Wait for two or three more runs, that's all. I just hope I'm not costing people's lives posting wrong infos.
Member Since: August 1, 2011 Posts: 28 Comments: 7981
Ok, the GFS has started the output. If anyone with more skill than I would take a look 00hr position and tell me if that looks like the right spot to initialize Irene or not. tia
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Quoting P451:


I don't know about a reform but watching the storm wind up on satellite I would not be surprised to see a northward jog followed by a resumed westward movement of the center.

You can see as the storm tightens up the southern reaches are being pulled up into the overall circulation.



LOL.

It has that look that you drew earlier, good job.
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Quoting sarahjola:
what is that churnning by the yucatan just in the gom?


Harvey
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what is that churnning by the yucatan just in the gom?
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1280. Mucinex
Quoting hunkerdown:
Sorry, I just can't...unless they brought in the former met Bill Kamal (it would just be comical, you know where ever he is he is dying to take the lead for this storm...)
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.

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this is what the 18z gdfl is depicting except the gdfl was farther north and much stronger..
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1278. Patrap


TS IRENE Floater - Water Vapor Loop


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1277. Gorty
Wow, is Dr. Masters seriously thinking we will enter the greek alphabet again? Kudos to him to venture in to an idea that goes way beyond what JB has ever thought of!
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1276. rv1pop
Quoting GoWVU:


Press my wife has already started, god help me!!
He will. Psa 91.
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ECMWF



NOGAPS



GFS



CMC

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1273. Grothar
Quoting hurricanehunter27:
Lol i know im just stating it about the model.


I know, I was just trying to be funny. Although, I have seen many storms move over Hispaniola and Cuba and become Hurricanes again. It depends on the strength of the system the time spent over land and the upper steering current. Those waters are very warm and many storm have been know to re-form quickly.
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GFS Initialization:

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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.