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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1871. scCane
Canadian Model

Link

New Edit: ugh beaten
Member Since: Posts: Comments:
1870. Patrap
Nothing like the first wisp the first feeder swirling in from the Seast..


Salty and cool..then Humid and Hot..

Buckle up..

Itsa gonna get a tad Bumpy..

Member Since: July 3, 2005 Posts: 426 Comments: 128749
1869. wxhatt
models shifting East again. Looking more like staying just offshore FL and heading North!
Member Since: October 5, 2005 Posts: 2 Comments: 927
We also need to take in account that in all likely hood, the east side of this storm will be the dirtiest. So lets say this scraps the west coast of Florida, affects would be worse for central and eastern Florida. If it hugs the east coast, effects may not be that intense. It all depends really, wait and see but be prepared.
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1867. gugi182
How far do the Tropical Storm force winds out of Tropical Storm Irene extend from the center?
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1866. Mucinex
1503. CaneAddict 4:03 AM GMT on August 21, 2011

Quoting Mucinex:

I also lost a car. Hence the reason I refuse to forgive Max Mayfield for not putting up the Hurricane Warning till after Irene had passed the county line. Car was pretty water tight though. I pushed it 1 1/4 miles which wasn't that hard because it was floating soo well.

The NHC is the only ones that put up hurricane warnings.

Max was the director of the NHC at the time.;)
Member Since: Posts: Comments:
You would think they would have a plane in there this close to land.
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Quoting ProgressivePulse:
I guess this image could freak out the untrained eye.


that puts the eye at 15.4N AND 60.0W.....LOLOLOLOL
Member Since: September 18, 2010 Posts: 0 Comments: 5234
shes been working out and looks tighter however i doubt she is verticly stacked atm
Member Since: May 18, 2009 Posts: 0 Comments: 171
Quoting dfwstormwatch:

hwrf is acting painfully slow tonight and the 0hour image still has not loaded



ok
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
South Florida hit on the 00z CMC. 108 hours:

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting AegirsGal:
It'll do that if you are using Internet Explorer.


Tools/Compatibility View should fix it. Enable and refresh.
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1858. Drakoen
Center around 16.9N 60.1W.

Member Since: October 28, 2006 Posts: 57 Comments: 30565
Quoting Tazmanian:
where is my be loveing dfwstormwatch with the mode runs



am this kinding on the be loveing part
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
Quoting Gearsts:
RI? Where do you get this info?


dvorak
Member Since: August 22, 2006 Posts: 2 Comments: 1983
Quoting Drakoen:
I think Irene has relocated her center further north based on radar imagery.


Are you using this radar imagery I've just become hooked to?

Link
Member Since: September 15, 2009 Posts: 497 Comments: 3688
Quoting Tazmanian:
where is my be loveing dfwstormwatch with the mode runs

hwrf is acting painfully slow tonight and the 0hour image still has not loaded
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1852. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128749
1851. Hurricanes101
4:58 AM GMT on August 21, 2011
Quoting MississippiWx:


I am very aware of it...We are discussing the track of the GFS. The track of the GFS has been our argument the whole time...not other possible tracks, which is what the NHC is referring to.


The NHC also has stated numerous times that intensity is very hard to predict and the basis for your whole argument is using an intensity forecast that is 5 days away based on the GFS track.

The track of the GFS is similar to many other models that have shown this system staying strong despite land interaction. The models have been showing this consistently for days, its not something that just came out of nowhere
Member Since: March 10, 2010 Posts: 1 Comments: 7826
1850. Patrap
4:58 AM GMT on August 21, 2011
Member Since: July 3, 2005 Posts: 426 Comments: 128749
1849. MahFL
4:58 AM GMT on August 21, 2011
RI on ? eeek
Member Since: June 9, 2004 Posts: 0 Comments: 3547
1848. DookiePBC
4:57 AM GMT on August 21, 2011
Quoting ProgressivePulse:
I guess this image could freak out the untrained eye.




It is scary yes...but not as scary as the Rainbow which constantly shows DOOOOOOM!!

Member Since: September 1, 2009 Posts: 0 Comments: 447
1847. lottotexas
4:57 AM GMT on August 21, 2011
Quoting angiest:
Quoting lottotexas:
The problem with that , is if it shifts west it'll get you anyway. Had the same thing with Rita. People evacuated Houston to East Texas and got slammed.

If I'm not mistaken, IH-10 east does not have an evaculane. I suppose that means they don't want people going that way.
Many went up 59 and got bogged down in traffic in the small towns in e Texas and were caught there when Rita went through.
Member Since: December 3, 2010 Posts: 0 Comments: 54
1846. mynameispaul
4:57 AM GMT on August 21, 2011
Quoting HurricaneHunterJoe:
i guess we got east casters and west casters? east want a atlantic seaboard hit? and west casters want a gulf coast hit> and the north and south casters? what do they want?


I really don't want a major hurricane coming at me. Rita left me scarred for life. Sat thru that one almost all night long and don't want no more of that.
Member Since: September 20, 2005 Posts: 0 Comments: 369
1845. Tazmanian
4:57 AM GMT on August 21, 2011
where is my be loveing dfwstormwatch with the mode runs
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
1844. TropicalWeatherGrl88
4:57 AM GMT on August 21, 2011
Quoting Hurricanes101:


ok guess you are right and every single model run for the last 4 days is dead wrong by keeping the storm strong



I think it has certainly been longer then 4 days it has been keeping it very strong. I myself am not sure why, but we will find out in 6 days if it verifies.
Member Since: September 17, 2010 Posts: 0 Comments: 216
1843. GTcooliebai
4:57 AM GMT on August 21, 2011
Well now, what do we have here:

Member Since: August 31, 2009 Posts: 0 Comments: 5628
1842. Patrap
4:57 AM GMT on August 21, 2011
Member Since: July 3, 2005 Posts: 426 Comments: 128749
1841. MississippiWx
4:57 AM GMT on August 21, 2011
Quoting HurricaneHunterJoe:
i guess we got east casters and west casters? east want a atlantic seaboard hit? and west casters want a gulf coast hit> and the north and south casters? what do they want?


Haven't really seen anyone "casting" it to themselves. Arguments tonight have been on intensity. Of course, all the PR people think it's coming to them. :-)
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1840. serialteg
4:56 AM GMT on August 21, 2011
Quoting ProgressivePulse:
I guess this image could freak out the untrained eye.




dude, if u lived where i live it would freak u out too regardless of the time u spend tracking
Member Since: August 22, 2006 Posts: 2 Comments: 1983
1839. ProgressivePulse
4:56 AM GMT on August 21, 2011
Quoting yesterway:


I used to love to camp at Jonathan Dickenson State Park and surf at Juno Beach...


Love it here although, millions of dollars are spent every year trying to save the pristine beaches, still awesome though.
Member Since: August 19, 2005 Posts: 5 Comments: 5450
1837. MiamiHurricanes09
4:56 AM GMT on August 21, 2011
00z CMC on board with the GFS/ECMWF/HWRF camp with the cyclone moving into the Bahamas region. Model out to 96 hours right now:

Member Since: September 2, 2009 Posts: 130 Comments: 21194
1836. NCHurricane2009
4:56 AM GMT on August 21, 2011
Quoting angiest:


That's what I take it to mean.


Wait a minute...and that same Dvorak post shows a fix of 16.6N....does that mean it is indeed centered further north after all?! That's what my hunches have been telling me every time I look at Irene tonight....
Member Since: September 15, 2009 Posts: 497 Comments: 3688
1835. Gearsts
4:56 AM GMT on August 21, 2011
Quoting KEEPEROFTHEGATE:
T.C.F.W
09L/TS/I/C0
RI FLAG "ON"
MARK
16.60N/60.10W
RI? Where do you get this info?
Member Since: August 2, 2010 Posts: 0 Comments: 1804
1834. Patrap
4:56 AM GMT on August 21, 2011
Member Since: July 3, 2005 Posts: 426 Comments: 128749
1833. ChrisDcat5Storm
4:56 AM GMT on August 21, 2011
Quoting CaneHunter031472:
If in the next 12 hours Irene does not start taking a wnw trajectory, the chances for it to miss hispaniola will be greatly increased and the longer it maintains this W trajectory, the greater the chance for it to just skirt the islands and make it to the GOMEX. It's all about the timing.




its alrdy moving wnw have u not seen the loops from the NHC
Member Since: May 18, 2009 Posts: 0 Comments: 171
1832. Drakoen
4:55 AM GMT on August 21, 2011
I think Irene has relocated her center further north based on radar imagery.
Member Since: October 28, 2006 Posts: 57 Comments: 30565
1831. reedzone
4:55 AM GMT on August 21, 2011
If Irene tracks more to the north, hits Hispaniola, she should have no problem re-strengthening in the Bahamas. She will also have more time over water if that happens and the EURO could be right. The EURO shows Hurricane Irene moving parallel of FL East Coast. Irene looks like she wants to strengthen quite a bit tonight. It's be interesting to see what happens.
Member Since: July 1, 2008 Posts: 13 Comments: 7396
1830. MississippiWx
4:55 AM GMT on August 21, 2011
Quoting Hurricanes101:


you are aware of what the NHC posted in their discussion in regards to the intensity right?


I am very aware of it...We are discussing the track of the GFS. The track of the GFS has been our argument the whole time...not other possible tracks, which is what the NHC is referring to.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1829. Walshy
4:55 AM GMT on August 21, 2011
Member Since: May 17, 2009 Posts: 2 Comments: 904
1828. Hou77083
4:55 AM GMT on August 21, 2011
Quoting HoustonTxGal:
Off topic question..... Has anyone else had problems with posts running off the page and not be able to be seen? I have refreshed several times and it will not correct.


Something to do when people post youtube graphics, just go to the next page and it will correct itself.
Member Since: July 5, 2010 Posts: 0 Comments: 110
1827. stillwaiting
4:55 AM GMT on August 21, 2011
charley,charley,charley scenerio imo
Member Since: October 5, 2007 Posts: 20 Comments: 4970
1826. HurricaneHunterJoe
4:55 AM GMT on August 21, 2011
i guess we got east casters and west casters? east want a atlantic seaboard hit? and west casters want a gulf coast hit> and the north and south casters? what do they want?
Member Since: September 18, 2010 Posts: 0 Comments: 5234
1824. angiest
4:55 AM GMT on August 21, 2011
Quoting NCHurricane2009:


What's the significance...is that the Dvorak stuff saying the rapid intensification flag is on right now?


That's what I take it to mean.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1823. ProgressivePulse
4:54 AM GMT on August 21, 2011
Quoting Drakoen:
There is a bit of a northerly component to Irene's movement. Will be interesting to see how that evolves over the next 24 hours.



Really leaning towards a direct hit on PR and north of the islands this evening.
Member Since: August 19, 2005 Posts: 5 Comments: 5450
1822. Bluestorm5
4:54 AM GMT on August 21, 2011
GFS run ends. Look how much rain SE USA is going to get at the end of Irene.



Member Since: August 1, 2011 Posts: 28 Comments: 8031
1821. MiamiHurricanes09
4:54 AM GMT on August 21, 2011
Quoting MississippiWx:


It has already been discussed here, even by Levi, that the models are probably underestimating the effects of land.
I guess we'll see, lol. I don't believe land interaction will be that bad. The GFS only has Irene inland over Cuba for a few hours whilst it's over eastern Cuba. The NHC has it inland for longer than that, hence the lesser intensity.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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