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 farhaonhebrew:
no hurricanes since George....1998... 13 years ...
Well get ready and be safe! Hopefully won't be too bad!
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Quoting MiamiHurricanes09:
Indeed. A rough track that I just drew up, evidently lol.



Looks good.. Irene also looks to have strengthened into a 60 mph. storm, but they will probably keep her at 50 mph. at 5 a.m.
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Quoting MiamiHurricanes09:
Indeed. A rough track that I just drew up, evidently lol.



A little bit further north than that and Irene is really going to ramp up.
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Quoting TomTaylor:
leave the poor troll alone lol

seriously tho, he's just hear to cause a ruckus, no need to waste your time. Night shift is supposed to be the peaceful chill hour let's keep it that way


Yeah, I just ignored it. Pretty sure it's JFV. It always says the same thing about Mississippi and then brings Taz up out of no where.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting TomTaylor:
yes, I agree...in which case is would miss Cuba resulting in much less land interaction and a stronger storm.
Indeed. A rough track that I just drew up, evidently lol.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting prtr4192:


i for one like the fact you are willing to take stand on a pattern and stick with it. as i recall they were
all over you when you were discounting emily.

thanks


Ehh, I wasn't discounting Emily.. I thought she would at the most ramp up to a strong TS/minimal Hurricane and ALMOST make a brief landfall near Miami or South Florida.. Instead, she ended up being a depression after re-emerging from a very bad environment. It seems that Irene will not have it as bad.. Especially when she looks to be well stacked already. Emily was never well stacked.
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Quoting ClydeFrog:
no it means I live in STT and am waiting for Irene, so that would be why I am up... What is your excuse except having no wife and education? lol losers... just like Taz.... education helps everything MS....


Education cannot give a person integrity and morals...
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Quoting ClydeFrog:
This is all too funny, bunch of idiots second guessing people with actual educations.... Mississippi get a life and an education. Your from MS so we know you have the education level of a typical person from MS. Time for a life I think if your on here at 4 am.... Get an education


People confuse education with intelligence, you can have one without the other. You make a perfect example!
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Quoting reedzone:


Then you would have the first idea of the models taking it up the spine of Florida.. The TX ridge is too powerful for any tropical system to break through. This is most likely not heading into the GOM.


Reed you seem hellbent on the storm being right on the east coast of florida not sure if you mean riding up I95 or the turnpike...but you are very specific. All some are saying is it is reasonable and possible that it could miss south florida by a bit as it make its turn north. Very possible. Exactly where Irene ends up turning, intensity and of course the ridge all play a role. Oh and not to mention the significant land interaction potential and the wobbles, reformation of center...etc that ALL could play a role in where she ends up. Are you open to a 100 mile error potential in your 5 day forecast?? If you are it could miss Florida, right?
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Quoting overwash12:
Probably see hurricane conditions Sunday night!
no hurricanes since George....1998... 13 years ...
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Quoting ClydeFrog:
no it means I live in STT and am waiting for Irene, so that would be why I am up... What is your excuse except having no wife and education? lol losers... just like Taz.... education helps everything MS....
Shouldn't that be more like: "Except not having a wife, and no education." Education would surely help you build better sentences ;) Maybe you should think about enrolling in an introductory English course?
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Quoting ClydeFrog:
no it means I live in STT and am waiting for Irene, so that would be why I am up... What is your excuse except having no wife and education? lol losers... just like Taz.... education helps everything MS....


Lol...This is pretty funny, JFV.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting ClydeFrog:
This is all too funny, bunch of idiots second guessing people with actual educations.... Mississippi get a life and an education. Your from MS so we know you have the education level of a typical person from MS. Time for a life I think if your on here at 4 am.... Get an education


Ewwww, who says this out of nowhere? You are very mean yo momma need to raide you better---->SLAP!!
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Quoting MississippiWx:


Wow, you're probably the biggest dumbass I've ever seen on the blog and that says a lot. Why don't you work on your grammar before you attack me about education?

And um, about the 4AM thing, it appears to me that you must be on at the same time as me. So that means that you should get a life as well?
leave the poor troll alone lol

seriously tho, he's just hear to cause a ruckus, no need to waste your time. Night shift is supposed to be the peaceful chill hour let's keep it that way
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Good morning all!

I wonder where the new models take Irene vis-a-vis the islands and it seems Florida is still the target down the road- by Friday?
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Quoting TropicalWeatherGrl88:


Then you understand why I feel this way. I watch a wave roll of Arica I think "will we get this one". It comes so...close but no, goes out to sea. Next one is on the way here and the cone is on us, nope it dissipates into NOTHING. That is why I feel let down, like a boyfriend is going to break up with me.:-) lol


I think every weather enthusiast feels adrenaline and excitement from seeing a storm. Despite the (understandably) ornery attitude some display when you make such a statement, I see no reason to get angry at such a notion myself. Despite all of our desires and wishing, ultimately the choice is not ours. Nature will do what it is going to regardless. It isn't like JFV wishing Irene to Miami is actually going to make it happen. If it does, he shouldn't feel bad for it.

But again, it's rather easy to see why most people ARE offended at such an idea. It's terrifying to them, not to mention downright disrespectful in most cases, given that many here have endured losses at the hands of these disasters. I would advise keeping opinions like that to yourself. It is why I do not respect JFV.
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Quoting farhaonhebrew:
Every body is sleeping here in P.R ... will be a mess when the people wake up with a hurricane watch or warning....
Probably see hurricane conditions Sunday night!
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Quoting reedzone:
Mississippiwx, I for one enjoy ur thoughts and forecasts on here. I think ur a very reliable source on here. The troll is just jealous.


Well, most people who have NEVER been to Mississippi say the things that he said. It's cool because it just shows their ignorance and I get a good laugh.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting reedzone:


Then you would have the first idea of the models taking it up the spine of Florida.. The TX ridge is too powerful for any tropical system to break through. This is most likely not heading into the GOM.


i for one like the fact you are willing to take stand on a pattern and stick with it. as i recall they were
all over you when you were discounting emily.

thanks
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2599. smuldy
ok well to all good night and good luck; time for my nap til 815am, weekend joy everyone stay safe
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Quoting MiamiHurricanes09:
All these late night shifts are screwing up my sleeping habits and now I can't fall asleep, plus, class starts tomorrow. Lol. Anyways, looking at satellite/radar, Irene definitely appears to be centered very near 17N. Am I the only one that could see Puerto Rico getting a direct hit and then the cyclone skirting along the north Hispanola coast? Definitely looks very plausible to me.

yes, I agree...in which case is would miss Cuba resulting in much less land interaction and a stronger storm.
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Mississippiwx, I for one enjoy ur thoughts and forecasts on here. I think ur a very reliable source on here. The troll is just jealous.
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Quoting MiamiHurricanes09:
All these late night shifts are screwing up my sleeping habits and now I can't fall asleep, plus, class starts tomorrow. Lol. Anyways, looking at satellite/radar, Irene definitely appears to be centered very near 17N. Am I the only one that could see Puerto Rico getting a direct hit and then the cyclone skirting along the north Hispanola coast? Definitely looks very plausible to me.

Quoting MiamiHurricanes09:
All these late night shifts are screwing up my sleeping habits and now I can't fall asleep, plus, class starts tomorrow. Lol. Anyways, looking at satellite/radar, Irene definitely appears to be centered very near 17N. Am I the only one that could see Puerto Rico getting a direct hit and then the cyclone skirting along the north Hispanola coast? Definitely looks very plausible to me.

Every body is sleeping here in P.R ... will be a mess when the people wake up with a hurricane watch or warning....
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Quoting MiamiHurricanes09:
All these late night shifts are screwing up my sleeping habits and now I can't fall asleep, plus, class starts tomorrow. Lol. Anyways, looking at satellite/radar, Irene definitely appears to be centered very near 17N. Am I the only one that could see Puerto Rico getting a direct hit and then the cyclone skirting along the north Hispanola coast? Definitely looks very plausible to me.



Ditto on the sleeping habits...
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Quoting KoritheMan:


Contrary to popular belief, I don't find that odd at all. Strong tropical storms can be fun, as long as they aren't too destructive.


Then you understand why I feel this way. I watch a wave roll of Arica I think "will we get this one". It comes so...close but no, goes out to sea. Next one is on the way here and the cone is on us, nope it dissipates into NOTHING. That is why I feel let down, like a boyfriend is going to break up with me.:-) lol
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DOOMcon still steady at GUARDED.

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Quoting reedzone:


Then you would have the first idea of the models taking it up the spine of Florida.. The TX ridge is too powerful for any tropical system to break through. This is most likely not heading into the GOM.


The Texas ridge is not why Irene is unlikely to find the Gulf Coast (at least, the northern and/or central Gulf); it's because the weakness being depicted in the models is too far east to allow much of a westward component of motion.
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Quoting ClydeFrog:
This is all too funny, bunch of idiots second guessing people with actual educations.... Mississippi get a life and an education. Your from MS so we know you have the education level of a typical person from MS. Time for a life I think if your on here at 4 am.... Get an education


Why does this blog offend you. If you are unhappy here go away. These people have done nothing to you for you to say such things. You are the one who needs to get a life my friend..
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Quoting washingaway:


What if the ridge builds a little further to the west?


Then you would have the first idea of the models taking it up the spine of Florida.. The TX ridge is too powerful for any tropical system to break through. This is most likely not heading into the GOM.
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Quoting KoritheMan:


Contrary to popular belief, I don't find that odd at all. Strong tropical storms can be fun, as long as they aren't too destructive.


SOmething about the excitement!!! I would say many on this board feel the same.
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Lol...There are no absolutes this far out.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
All these late night shifts are screwing up my sleeping habits and now I can't fall asleep, plus, class starts tomorrow. Lol. Anyways, looking at satellite/radar, Irene definitely appears to be centered very near 17N. Am I the only one that could see Puerto Rico getting a direct hit and then the cyclone skirting along the north Hispanola coast? Definitely looks very plausible to me.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting reedzone:


Not gonna happen.. Sorry.. The pattern will not allow it, as others have pointed out.

Patterns change dude....
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Quoting smuldy:
ya Kori you are def solid here; you kman levi and it seems bero def know your stuff always try to take in your take before offering mine

edit and miami and grothar and weatherguy03 cause i feel like a word i cant say on this blog not mentioning them as well


Thank you.

And yes, all those other guys are vastly knowledgeable as well. I really respect them.
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One thing for sure,we will have a hyper-blog today! Esp. Fl. bloggers.
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Quoting reedzone:


Not gonna happen.. Sorry.. The pattern will not allow it, as others have pointed out.
don't get too overconfident...
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Quoting reedzone:
New run, a bit late, but here it is.. As we all like to call it, the REED run ;)


It would take a die hard miracle for Irene to miss the coastline, the pattern literally forces the storm up the coastline. 00Z EURO has a Category 3 storm just off of Flagler Beach in 144 hours (7 days)


What if the ridge builds a little further to the west?
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Quoting TropicalWeatherGrl88:


Oh trust me I am not wishcasting if I was I would like to get hit by a nice TS, yes that probably sounds weird. I like the air, and the rain, and the wind. I am just disappointed I may not get to experience it! I hope you are right btw.


Contrary to popular belief, I don't find that odd at all. Strong tropical storms can be fun, as long as they aren't too destructive.
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All I know is Irene is north of the trop pts on the nhc loops. Should be an interesting new cone and couple of days ahead.
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Quoting reedzone:
My forecast of the models to switch up the East Coast of Florida was right on! Expect the NHC track to point right at Miami at 5 a.m. as either a 70 mph. storm or minimal Hurricane. No this is NOT going out to sea, even scottsvb, who is a MET, can be off. This is not missing Florida, the pattern strictly pulls this right up the coastline.


You may be right but so many "runs" and things to happen in the coming days before I would clap for forecast verification. If Irene ends up just a little north of forecast while going thru carib, the slow bend northward may allow it to miss SOUTH florida while moving ashore in central or north florida, Georgia etc. Irene has already readjusted north and most models have shifted east already. ANY further east shift in the coming days and Florida may get lucky. Just saying this cuz I believe a west shift is unlikely. So either the models are spot on right now well out in advance or they shift just a bit east, missing S florida. Just IMO only!!
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New run, a bit late, but here it is.. As we all like to call it, the REED run ;)


It would take a die hard miracle for Irene to miss the coastline, the pattern literally forces the storm up the coastline. 00Z EURO has a Category 3 storm just off of Flagler Beach in 144 hours (7 days)
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Definitely a nice looking circulation.
Member Since: August 11, 2010 Posts: 0 Comments: 784
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Every body is sleeping here in P.R ... will be a mess when the people wake up with a hurricane watch or warning....
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Quoting KoritheMan:


It's true that you can never be certain in weather. I guess we'll see. But right now, I just don't see it. Anyone that knows me understands I don't wishcast -- I forecast. Big difference.


Oh trust me I am not wishcasting if I was I would like to get hit by a nice TS, yes that probably sounds weird. I like the air, and the rain, and the wind. I am just disappointed I may not get to experience it! I hope you are right btw.
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Quoting TropicalWeatherGrl88:


Don't get to happy just yet it may shift more to the east over time seems to have a eat bias due to intensity


Not gonna happen.. Sorry.. The pattern will not allow it, as others have pointed out.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.