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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2321. Patrap
2km Storm Relative IR Imagery with BD Enhancement Curve


Member Since: July 3, 2005 Posts: 426 Comments: 128654
Quoting charlottefl:
I'm gonna be a little bolder than I normally am, but I think it needs to be said and I'll leave it at that. Irene's ultimate destination is YTBD, but the thinkin that 60 miles of a reformation to the north=100's of miles to the east track wise is well, skewed. As of right now Irene appears to be moving fairly close to due W, with a small center reformation to the north. Calling for drastic changes in the models does not make any sense to me. Now if some serious deviation to the North occurs after this point, that may be plausible, but I don't see it happening given the synoptic pattern that is in place. You may change the starting point, but unless you alter the pattern, the destination remains (roughly) the same.


I have to disagree. Irene could now completely miss Cuba. Granted it takes it more over the meat of Hispaniola but, not Cuba. Starting a point 60NM north of what was modeled will have rather large implications down the line moving WNW. Have to see what tomorrow holds and what recons truths tell.
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Quoting HurricaneHunterJoe:


thought i saw a post earlier that the GFDL was the one model to be getting it right!! oops i guess not,now that it's gonna be a east coaster or carolina strom


Far from the truth right now.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
center now under deep convection
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2317. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 174 Comments: 54370
2316. 7544
Quoting WaterWitch11:
dang, i just looked at the satellite it looks like irene will get big.


looks at the visable no kidding is that --e i cant say it lol
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Quoting MiamiHurricanes09:
Well, DAMN!

Hurricane Hazel, anyone?



Not saying it will happen, but that what this model is suggusting... wow. How's that for my first hurricane :\
Member Since: August 1, 2011 Posts: 28 Comments: 8030
MH09, where do you think Irene is going?
Member Since: June 21, 2010 Posts: 0 Comments: 528
Quoting RyanFSU:
GFDL 00Z doomcast:



And Animation of Inner nest: Link


thought i saw a post earlier that the GFDL was the one model to be getting it right!! oops i guess not,now that it's gonna be a east coaster or carolina strom
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scary to say the least so far.....models in consensus over approx a week.....predicted a blowup in organization and convection on sat at the leewards, and POOF.....here we go.....
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Irene is stronger than 50mph...

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Yes the island of the Enchantment won't be to pretty tomorrow night, it looks like a direct hit from Irene as a Cat 1,similar in strength to Hurricane Hortence in 1996, so we have only a few hours to prepare... buenas noche..
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Quoting MississippiWx:
Euro 96...looks similar to GFS

Not much interaction with Cuba. Mainly Haiti.
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Quoting MiamiHurricanes09:
Well, DAMN!


exactly
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Quoting Drakoen:
The 00z HWRF is pretty much east of Florida and the 00z GFDL is west of Florida. lol


i just love models
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dang, i just looked at the satellite it looks like irene will get big.
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Euro 96...looks similar to GFS

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting AllStar17:
They relocated it to 16.0N 60.4 W


that looks to be close
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2302. scott39
Quoting weatherman12345:
? not for the islands
Wasnt trying to imply lack of impathy for the Islands.
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2301. Drakoen
Quoting Stormchaser2007:


It could even be as far north as 16.9

We'll have to wait for recon.


Thanks for the vote of confidence lol
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96 hours

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2299. JLPR2
Quoting TomTaylor:
Latest NHC coordinates vs last NHC position and model consensus tracks (TVCs).





Such a northward shift could allow it to miss Cuba, and the most mountainous parts of Hispaniola...


I expect them to be more or less the same, just farther north. :\
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UKMET still like the GFDL:

TROPICAL STORM IRENE ANALYSED POSITION : 14.3N 59.4W

ATCF IDENTIFIER : AL092011

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 21.08.2011 14.3N 59.4W WEAK
12UTC 21.08.2011 16.2N 62.8W WEAK LITTLE CHANGE
00UTC 22.08.2011 16.8N 65.8W WEAK INTENSIFYING SLIGHTLY
12UTC 22.08.2011 16.7N 69.2W MODERATE INTENSIFYING SLIGHTLY
00UTC 23.08.2011 17.5N 70.7W INTENSE INTENSIFYING RAPIDLY
12UTC 23.08.2011 17.7N 74.5W MODERATE WEAKENING RAPIDLY
00UTC 24.08.2011 18.4N 76.1W MODERATE LITTLE CHANGE
12UTC 24.08.2011 19.1N 78.6W MODERATE INTENSIFYING SLIGHTLY
00UTC 25.08.2011 19.6N 80.8W STRONG INTENSIFYING SLIGHTLY
12UTC 25.08.2011 20.8N 82.9W STRONG INTENSIFYING SLIGHTLY
00UTC 26.08.2011 21.7N 85.0W INTENSE INTENSIFYING SLIGHTLY
12UTC 26.08.2011 22.9N 86.7W INTENSE LITTLE CHANGE
00UTC 27.08.2011 23.8N 88.0W INTENSE LITTLE CHANGE
Member Since: July 15, 2006 Posts: 17 Comments: 10284
2297. Patrap
Enhanced Infrared Loop (IR) Imagery (4 km Mercator)
Member Since: July 3, 2005 Posts: 426 Comments: 128654
Quoting MississippiWx:
Ya know, IR would really support the center being at where radar is showing. This image of IR is 45 minutes old. A due west motion looks to be occurring right now on radar.



i agree,looks like we has a re-location of some sort and now back to west, we will have to watch it
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Quoting TomTaylor:
Latest NHC coordinates vs last NHC position and model consensus tracks (TVCs).





Such a northward shift could allow it to miss Cuba, and the most mountainous parts of Hispaniola...


It could even be as far north as 16.9

We'll have to wait for recon.
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Quoting charlottefl:
I'm gonna be a little bolder than I normally am, but I think it needs to be said and I'll leave it at that. Irene's ultimate destination is YTBD, but the thinkin that 60 miles of a reformation to the north=100's of miles to the east track wise is well, skewed. As of right now Irene appears to be moving fairly close to due W, with a small center reformation to the north. Calling for drastic changes in the models does not make any sense to me. Now if some serious deviation to the North occurs after this point, that may be plausible, but I don't see it happening given the synoptic pattern that is in place. You may change the starting point, but unless you alter the pattern, the destination remains (roughly) the same.
I agree, just take a look at the steering charts, and the models don't show this north of of PR or Hispaniola either.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting Patrap:
TS IRENE Floater - Water Vapor Loop

that looks to be going west on that view,and the LLCon the sw side
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2292. Patrap
Enhanced Infrared (IR) Imagery (4 km Mercator)

AL092011 - Tropical Storm IRENE



Member Since: July 3, 2005 Posts: 426 Comments: 128654
Such a northward shift could allow it to miss Cuba, and the most mountainous parts of Hispaniola...
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2290. scott39
Quoting charlottefl:
I'm gonna be a little bolder than I normally am, but I think it needs to be said and I'll leave it at that. Irene's ultimate destination is YTBD, but the thinkin that 60 miles of a reformation to the north=100's of miles to the east track wise is well, skewed. As of right now Irene appears to be moving fairly close to due W, with a small center reformation to the north. Calling for drastic changes in the models does not make any sense to me. Now if some serious deviation to the North occurs after this point, that may be plausible, but I don't see it happening given the synoptic pattern that is in place. You may change the starting point, but unless you alter the pattern, the destination remains (roughly) the same.
+1000
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Quoting weatherman12345:
2 lows?


No, just a broad circulation being depicted.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting weatherman12345:
2 lows?
It's showing that nonsense again?
Member Since: August 31, 2009 Posts: 0 Comments: 5628
72:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting Jedkins01:
Also we can't assume relocation to the north is occurring its a tropical storm, they are always often more disorganized as far as where the center is then they often look. Also keep in mind, that if it does relocate further north, that doesn't necessarily impact the long term forecast much. It really all depends on how the 2 highs and the weakness between them interacts 5 days from now, as well the effects of the incoming trough.
16N. from 15.3N a .7 degree difference and still moving west at 22mph as of the 2am advisory. And your thinking on the steering is the same as my thinking.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Wouldn't be surprised if the next recon finds Irene to be a hurricane already...might be a major before any significant land interaction occurs.
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2283. scott39
If Irene starts a W to WNW track now.....She will look worse than Emily did at her worst... GOING OVER ALL THOSE ISLANDS! That would be GREAT news!!
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Quoting RyanFSU:
GFDL 00Z doomcast:



And Animation of Inner nest: Link
Hey Dr. Maue, just wanted to say you have a great website, thanks for keeping that up to date.
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2280. scCane
New Edit: beaten
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I'm gonna be a little bolder than I normally am, but I think it needs to be said and I'll leave it at that. Irene's ultimate destination is YTBD, but the thinkin that 60 miles of a reformation to the north=100's of miles to the east track wise is well, skewed. As of right now Irene appears to be moving fairly close to due W, with a small center reformation to the north. Calling for drastic changes in the models does not make any sense to me. Now if some serious deviation to the North occurs after this point, that may be plausible, but I don't see it happening given the synoptic pattern that is in place. You may change the starting point, but unless you alter the pattern, the destination remains (roughly) the same.
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Euro 48 hours:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting Jedkins01:
Also we can't assume relocation to the north is occurring its a tropical storm, they are always often more disorganized as far as where the center is then they often look. Also keep in mind, that if it does relocate further north, that doesn't necessarily impact the long term forecast much. It really all depends on how the 2 highs and the weakness between them interacts 5 days from now, as well the effects of the incoming trough.


Agreed.
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Quoting scottsvb:
First off People get ahold of yourselves.. This storm is just beginning.

2ndly... The COC is still on the SW side of the convection near 15.7N or we will know when recon goes out there.. yeah they will do a 2am cords from the NHC but they need recon cause even radar imagry is poor right now due to the midlevel COC alittle to the NE of the LLC.

3rd... There is too much time and things that can make this go east of Florida mostly affecting the bahamas or even into the GOM. We will have a better idea by 00Z runs tomorrow and even better by Monday-Tues when we know how much land interaction took place with Hispaniola and then Cuba on Weds. Hispaniola might knock off the LLC and push it more W while the midlevel center moves WNW north of Haiti... we just dont know yet. So lets not think of Florida or where it will go until we see what it does in Hispaniola and where it comes off and how strong this is still.
THANK YOU FOR SOME SANE INPUT!!
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Dunno if anybody else has said it yet, but a track across PR will not cause this storm to miss FL. Instead, it would likely move WNW to NW along the north coast of Hispaniola and through the TCI and Bahamas. Then models split on whether it goes through the Keys or up along the E FL coast and north from there. I haven't seen a single model for about 5 days now that misses FL altogether.
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Quoting charlottefl:


Not enough frames to say, but if you do long term averages off sat and radar it's fairly close, may be as much as 285, but I don't think any more.



Agreed.

BTW, go Gators......NOT! :D

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Quoting MississippiWx:


It's not like the GFDL isn't a doomcast. Lol.

Well not that farfetch'd imo, if it interacted with the mountains of Haiti the storm could stay the same or weaken, which would ensue a more westward track & give it more time over water to re-intensify.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
2272. Drakoen
Quoting BahaHurican:
Kinda late for this to be a fish storm; it's going to hit the Leewards and possibly PR in the next 24 hours. Likely to hit the DR after that, and then either Cuba, the Bahamas, or both by mid week. So even if it doesn't devastate the US East Coast, it will have gotten its licks in....

A bit easier to do because they have the Meteo-France Radars there?



That may be true. If the center seen on radar imagery is mid level, then the question becomes how is the mid leve center displaced from the low level center if Irene is under 3 knots of shear as analyzed by the SHIPS output?
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2271. Patrap


Member Since: July 3, 2005 Posts: 426 Comments: 128654

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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.