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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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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Quoting TampaFLUSA:
The last direct hit was before we were born. I tried looking up the last tome we had 90 plus winds...all I got was hurricane Easy in 1950 and Donna in 1960.
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.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting GoWVU:
Well the local weather here in Charleston is talking about Irene for next weekend. I know lots can change but they are talking about her just to keep an eye on her.


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...
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I've seen it time and time again. Storms that are loaded to one side tend to have a bias towards that direction. NHC was smart to mention the risk to PR, it could verify.
Member Since: August 19, 2005 Posts: 5 Comments: 5449
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...)
LMAO!! Sorry...that made me spit out my soda.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1215. wxhatt
Look, Irene kinda looks like a roulette wheel. Round and round she goes where she stops, nobody knows!

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HWRF is suggusting 160 mph Category 5 hurricane? I am not buying this AT ALL.
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Quoting GTcooliebai:
I have a feeling there is going to be some looong sleepless nights for some folks.


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.
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Quoting Grothar:
Thats how perfect conditions are. But i dont think it takes in account of landmasses.
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Quoting MiamiHurricanes09:
WSVN "The Hype Station"'s take on Irene from the 10p.m EDT newscast.
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...)
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Quoting BahaHurican:
Let's not go replaying Wilma, now....



sorry could not help it lol
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Link

If just don't see PR avoiding severe conditions as well as the Northern Leeward and Virgin Islands. Irene's northern expansion is amazing.. is still getting wider each frame.
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http://www.youtube.com/watch?v=UfVQ2C5_hfI&feature= youtube_gdata_player
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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)
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Complete Update

Nothing like that warm fuzzy feeling you get looking at the 4's & 5's on the Model tracks.

TS BUSTED FORECAST ALIBI






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Quoting TheMom:
I thought twc was only mentioned here in mocking and of course tracking of the hot bald guy...


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

Look at the bottom of the discussion.


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....
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1200. GoWVU
Quoting presslord:


'Chucktown' here on Jeff's blog is one of our TV mets...he's at ch5...not sure he'd want me to say his name here...


Good information to know,thanks for sharing. I am Rob Fowler guy, I know diffrent station but that is the station I watch.
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what is that churnning by the yucatan just in the gom?
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Quoting hurricane23:


No way thats coming to pass... I expect futher westward shifts in the globals later tonight i.e; GFS and EURO.


What's your reasoning?
Member Since: July 15, 2006 Posts: 17 Comments: 10282
Quoting PcolaDan:


And even more useless trivia.

A raisin dropped in a fresh glass of soda will bounce up and down continually from the bottom of the glass to the top.


LOL - that is good.
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1195. TheMom
Quoting dfwstormwatch:
hmm you think its coincidence that twc showed the major hurricane hitting Savannah and the major hurricane hitting Miami it could happen tomorrow episodes a hour or two ago?
I thought twc was only mentioned here in mocking and of course tracking of the hot bald guy...
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Quoting Tazmanian:
would t it be some in if we go too bed has a 50mph TS and wake up too a 882mb and 190mph winds in the AM



heh heh heh
Let's not go replaying Wilma, now....
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The HH'ers are based in St Croix. If at take off time at 8am, and the wind is blowing a gale. Would they cancel the flight and send another plane into Irene from Biloxi??
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Quoting 7544:


how strong is that hwrf please tia

You don't even want to know... it's suggusting a major hurricane toward Florida, but don't buy any of models for hurricane strength just yet.

EDIT: 141 knots according HWRF... don't buy this yet.
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Quoting Grothar:


No way thats coming to pass... I expect futher westward shifts in the globals later tonight i.e; GFS and EURO.
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Quoting HoustonTxGal:
More useless trivia... It has been 1071 days since a hurricane hit the US. THe last one was Ike in 2008


And even more useless trivia.

A raisin dropped in a fresh glass of soda will bounce up and down continually from the bottom of the glass to the top.
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1189. 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! :)
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Quoting MiamiHurricanes09:
WSVN "The Hype Station"'s take on Irene from the 10p.m EDT newscast.


Awesome studio.
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Quoting GoWVU:
Well the local weather here in Charleston is talking about Irene for next weekend. I know lots can change but they are talking about her just to keep an eye on her.


'Chucktown' here on Jeff's blog is one of our TV mets...he's at ch5...not sure he'd want me to say his name here...
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1186. KEEPEROFTHEGATE (Mod)
T.C.F.W.
09L/TS/I/CX
MARK
16.63N/59.69W
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Good night everyone, join in on the Tropics talk, Tropicalanalystwx and caneswatch are on there, along with me, and if you want to join in(THERE's LIMITED AMOUNT OF TROLLS)...
lol thats a good advertisement, anyway gnite
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Quoting GTcooliebai:
Yeah
The last direct hit was before we were born. I tried looking up the last time we had 90 plus winds...all I got was hurricane Easy in 1950 and Donna in 1960.
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1183. 7544
Quoting barotropic:


HWRF intensity coming off cuba and approach

ing florida is nuts.


how strong is that hwrf please tia

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Quoting PcolaDan:

Took someone long enough. :)
I have a feeling there is going to be some looong sleepless nights for some folks.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting CaneAddict:


Check your mail...


Ditto.
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Quoting FLweather:
If Irene's motion is still west, and is suppose to gradually become WNW, it puts PR in imminent danger. If she turns WNW it looks as though she will cross PR and possibly encounter the northern edge of DR. She would have to continue moving west for more than the next 48 hours to even come close to Jamaica(which is what the GFDL is suggesting). I know her convection is displaced to the NE, but the convection is already north of PR. With the center gaining latitude and possibly reforming even further north, I don't see any way of PR avoiding a close call with Irene. Just my opinion...


My opinion is right in alignment with your opinion too......
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WSVN "The Hype Station"'s take on Irene from the 10p.m EDT newscast.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting NCHurricane2009:


Which agency made that statement about Puerto Rico....I don't see it in the NHC latest forecast....

...and the radar image IMO shows a storm already further north of the beginning of the NHC 11 PM cone...

Look at the bottom of the discussion.
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1177. Grothar
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Quoting CosmicEvents:
I think I'm going to sleep as well.
.
.
.
Good Night Irene.

Took someone long enough. :)
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Quoting P451:
moe doesn't have the 0z model runs yet so....


18Z HWRF




18Z GFDL



HWRF intensity coming off cuba and approaching florida is nuts.
Member Since: August 22, 2010 Posts: 0 Comments: 652
1174. Skyepony (Mod)
07E GREG


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1173. GoWVU
Well the local weather here in Charleston is talking about Irene for next weekend. I know lots can change but they are talking about her just to keep an eye on her.
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Quoting presslord:


Wow!! I guest authored an entry for Jeff Masters called 100 Days Which Changed So Much detailing our Ike relief efforts....amazing that was 971 days ago...


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)
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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.