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 stormhank:
Im near the tallahasse area..anyone think we would get much rain from this?? I saw the euro n gfs runs that after affecting florida they turn irene nw into georgia instead of out to sea??


So am I and it's just a wait and see....I am leaving town on Monday and a little worried but a relative is house sitting. I would not think that we have to worry too much unless the "angle" of land fall and the inland movement leaves us in the training pattern......Don't see that happening unless she comes in around the Panhandle and then moves NE into GA.
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Quoting Patrap:


how well Irene is moistening the environment!
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Quoting KEEPEROFTHEGATE:
JasonCoolMan2008



See ya!
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We wont have one of those strong troughs to really kick this system out. So it will be more of a gradual turn to the North. So if it does move East of Florida it could ride right up the East Coast.
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Quoting Bretts9112:

im seeing them more in the gulf or near FL what are you looking at?


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Quoting presslord:


basing evacuation on SS Cat status is not wise..
That's how the counties in South Florida define evacuation zones - on Category and direction storm is coming from. Not that I 100% think the government always makes the best decisions - LOL. Our worst storm in my experience came from the west, so storm surge has not been an issue in SE FL in the 18 years I have been here; just curious as to whether it is a real or hyped concern.
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Quoting weatherguy03:


And if it goes just East then the impacts will move up the coast towards South Carolina and North Carolina.


maybe she'll just buzzsaw the coast offshore...we just spent $28 million 'renourishing' Folly Beach...wouldn't take much to suck all that sand back into the sea...
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513. DFWjc
Quoting Bluestorm5:
Jason, face the REAL Tsar Bomba. 57 megaton of doom...

http://www.youtube.com/watch?v=LxD44HO8dNQ&fe atur e=related


Nah, just make him watch a Blues game from last year...LOL
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I'm still sorta surprised we're actually at the 9th storm.I thought this season would be less active than last year.or those who predicted 15.Well we only got 6 more storms to go.And we may very well reach that by mid September.
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Quoting hurricanejunky:


Hearing reports and stories on the 1935 Labor Day storm some say 200+ mph winds...even have heard 250 mph gusts but I think that may be a little too high.


At 892mb in the keys I would believe 200mph easily.
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I think some folks had 97l going down flagler street as a cat 4 three days ago
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Quoting Bretts9112:

almost like an ivan path but then again ivan is in the past
Ivan came in further south and may be in the past for some but for those of us in Grand Cayman he will always be in the here and now. Bad memories with Ivan.
Member Since: October 9, 2008 Posts: 0 Comments: 8436
Quoting KEEPEROFTHEGATE:
you do know hurricanes can exceed 200 mph right strip the land of everything even life so that nothing remains not but the dirt and the water
I was going to say that it could reshape the Geography of a whole entire Country, take Burma for example, Super Cyclone Nargis killed 138,000 people, and inundated the Country's coastline, towns and communities with water.
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If no one acknowledges or gives attention...
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Jason, face the REAL Tsar Bomba. 57 megaton of doom...

http://www.youtube.com/watch?v=LxD44HO8dNQ&featur e=related
Member Since: August 1, 2011 Posts: 28 Comments: 8074
I really do have to say this is going to be an extremely tough situation with regards to planning. What survives over the mountains, if anything, has the potential to rapidly intensify as is being depicted in the models and in the NHC discussion. Tough picking up a family and getting out of dodge 24hrs ahead of landfall. Money is tight with most everyone right now to further complicate the matter.
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Quoting ncstorm:


from 2004 bonnie, right up the road from me, we had 3 people died from a tornado then..I wouldnt call that weak..we just dont know what will happen and I really pray you are right..


That was a TS which skirted the coast. Different scenario than remnants coming up 5-600 miles inland.
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Quoting MississippiWx:
Interesting to see the models shifting east a little now that we have a classified storm. Keep pushing away from the Gulf!

im seeing them more in the gulf or near FL what are you looking at?
Member Since: June 22, 2010 Posts: 0 Comments: 140



Great example of BAM models as usually the case..........strong storm goes North as the BAMD is the furthest to the EAST while the BAMS is the furthest to the WEST!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting washingaway:
Cut it out coolman!


Jason is still here? good thing I have him on ignore.. what a d---bag
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what does it take for get banned??

- I'm referring to JasonCoolMan2008 - u r sick

- and there are kids on this site
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Quoting MississippiWx:
Interesting to see the models shifting east a little now that we have a classified storm. Keep pushing away from the Gulf!


Yeah and closer to the Bahamas. thank you MississippiWx... :P
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Quoting coffeecrusader:
Dr. Masters also said it wouldn't be a tropical storm until Tuesday. Isn't it Saturday?



oops
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The question:

Is Pottery still partying,

or soundly sleeping?
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Quoting washingaway:
Cut it out coolman!


I thing he's JFV, with a Jason name...
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492. DFWjc
Quoting washingaway:
Cut it out coolman!


I agree had to send my cousin out of the room...he's 8 and doesn't need to see that.
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Interesting to see the models shifting east a little now that we have a classified storm. Keep pushing away from the Gulf!
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Quoting Grothar:


No, I am just a little old, lonely man. Are you really in the Cone, or is your name just deceiving


Oh yes, as of this evening, I am InTheCone! Hopefully, I can escape somehow!
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Dr. Masters also said it wouldn't be a tropical storm until Tuesday. Isn't it Saturday?
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My ignore list isn't working... I can't ignore fake-Jason posting nasty pictures.
Member Since: August 1, 2011 Posts: 28 Comments: 8074
JasonCoolMan2008

xxx
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Quoting presslord:


yea...it's kinda hard to come up with a scenario which doesn't include Florida...


And if it goes just East then the impacts will move up the coast towards South Carolina and North Carolina.
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I just had to read over 1200 posts just to catch up...

SLOW THE HECK DOWN!

lol.
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Cut it out coolman!
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Quoting MSweatherguy:


I think if it does head to s florida that it would have to go over to much land so a cat 4 or 5 is highly doubtful.


Actually, there are a few paths it can take which it can miss land and hit South Florida.
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479. ackee
DR. ROB on crown weather makes good point on where the models seem to be trending for stronger HIGH track south of hispanola THEN BETWEEN jam and guess we see but that track being saying all along guess we will see
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Quoting ncstorm:


Unfortunately if I had to pick between a hurricane or a tornado, I would take the hurricane..at least you have more of a notice, tornados, probably about 30 minutes, top
Well, if I had to pick between Cat. 3-5 cane and EF 3-5, I'll take hurricane. I've survived many close call with weak tornadoes in St. Louis, but EF3 in NC is the closest I've been to violent one. I moved to NC in 2009, 2 years before EF4 struck 5 miles to north from my old house in Missouri. You are right, tornadoes had little warnings (Joplin was lucky that NWS knew tornado was coming 30 minutes before it happened, compaired to average of 15).
Member Since: August 1, 2011 Posts: 28 Comments: 8074
Im near the tallahasse area..anyone think we would get much rain from this?? I saw the euro n gfs runs that after affecting florida they turn irene nw into georgia instead of out to sea??
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GDFL, doom cast.

http://moe.met.fsu.edu/tcgengifs/

Hits Haiti, Jamaica, The Cayman's, then enters the Gulf at sub 920mb
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Quoting DontAnnoyMe:


Tornadoes spawned by tropical systems are not the same as those that are formed by supercells. Not even close. I've seen it here in Central NC for many years. There may be some damage, but it will be minimal.


from 2004 bonnie, right up the road from me, we had 3 people died from a tornado then..I wouldnt call that weak..we just dont know what will happen and I really pray you are right..
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Hey, I think Jaimito FV is back, impersonating Jason....

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Well, thanks Dr., but the blog broke it's own record. Despite your attempts to bring some realism to track and intensity possibilities, we devolved into "OMG, a Cat4 into Miami" in only 74 minutes.
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Thanks for the encouragement guys!
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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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