Irene roars into life; may become the season's first hurricane

By: Dr. Jeff Masters , 12:03 AM GMT on August 21, 2011

Share this Blog
29
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 371 - 321

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74Blog Index

Quoting benirica:
All those intensity models are initialized at 45... Aren't they all wrong then? Or is that chart in knots?


Always in knots.
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Grain of salt...

TVCN track with IVCN intensity is 128 knots over SFL.

GFDL has a Cat 5 in the GOM

HWRF has a Cat 4 near Miami

..Oof

FULL IMAGE (Recommended)



When models show it strengthening that high and it's this close, it's not to be taken with a grain of salt. It's to be taken seriously.
Member Since: Posts: Comments:
All those intensity models are initialized at 45... Aren't they all wrong then? Or is that chart in knots?
Member Since: Posts: Comments:
HWRF 18Z

Member Since: Posts: Comments:
AL, 09, 2011082100, 03, IVCN, 0, 0N, 0W, 45, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 12, 0N, 0W, 53, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 24, 0N, 0W, 65, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 36, 0N, 0W, 80, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 48, 0N, 0W, 90, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 60, 0N, 0W, 81, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 72, 0N, 0W, 87, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 84, 0N, 0W, 79, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 96, 0N, 0W, 83, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 108, 0N, 0W, 89, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 120, 0N, 0W, 95, 0, , 0, , 0, 0, 0, 0,
AL, 09, 2011082100, 03, IVCN, 132, 0N, 0W, 128, 0, , 0, , 0, 0, 0, 0,
Member Since: Posts: Comments:
Quoting BenBIogger:
12z JMA has Irene over the eastern Gulf of Mexico.


Can I please have a link to this model run? TIA
Member Since: Posts: Comments:
Quoting Ryuujin:
Levi,

I get the sense that with the models swinging to the right that some people seem to think Irene will swing off harmlessly away from the coast (that is a general feeling I'm getting) In your opinion what is the likelihood of that happening? Slim to none?


I can never say "none" with the weather, but definitely slim. In my opinion, this is coming for the United States somehow.
Member Since: Posts: Comments:
Quoting KoritheMan:
I am rather puzzled as to just how far south the GFDL is. The models have been consistently predicting that the weakness would be farther east, which is what I still think also.


GFDL runs as if a trough doesn't exist? Yet, GFS has been showing it every run, for what 10 days?
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting Stormchaser2007:
Grain of salt...

TVCN track with IVCN intensity is 128 knots over SFL.

GFDL has a Cat 5 in the GOM

HWRF has a Cat 4 near Miami

..Oof

FULL IMAGE (Recommended)

Well if Irene stays as far south in the Carribean and passes through the Yucatan then it's chances of being a Cat.5 isn't out of the question.However if it takes the northern track through the Islands it could weaken or get torn apart.
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Grain of salt...

TVCN track with IVCN intensity is 128 knots over SFL.

GFDL has a Cat 5 in the GOM

HWRF has a Cat 4 near Miami

..Oof

FULL IMAGE (Recommended)

Dang. What's worrisome is how much the cyclone will be able to intensify in the Bahamas region since atmospheric conditions will be primed for some RI as the HWRF and IVCN both reveal.
Member Since: Posts: Comments:
Quoting stormwatcherCI:
Earlier you said the tracks had it moving wsw in 12-18 hours. Maybe it was not actually moving wsw but rather relocating/reforming a center wsw. Is this possibly what they saw ?


They probably propagated the old broad low pressure circulation that was down near 11N yesterday and didn't see the northward reformation coming. To us it was obvious, but the model doesn't always get it.
Member Since: Posts: Comments:
center still not under deep convection
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Grain of salt...

TVCN track with IVCN intensity is 128 knots over SFL.

GFDL has a Cat 5 in the GOM

HWRF has a Cat 4 near Miami

..Oof

FULL IMAGE (Recommended)


Oh my jeezers!
Member Since: Posts: Comments:
Weather related accident.

Plane crash kills 12 in Canada's Arctic
Member Since: Posts: Comments:
Quoting presslord:


her mother is an old friend of mine...and if you keep talkin' about South Carolina...I may need to go visit them...


Alaska's a great place during the summer :) I hope you don't have to visit under forced circumstances though.
Member Since: Posts: Comments:
Quoting TampaSpin:


Ya i know i typed the wrong number......check out the graphic off the Coast of Africa was what i was referring too.......Sorry
Sorry for correcting ^^ I should had been paying attention about location.
Member Since: August 1, 2011 Posts: 28 Comments: 7913
Quoting MiamiHurricanes09:
I'd say the LGEM and DSHP in this case.

If so, Hispaniola could get a moderate Cat 1.
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Grain of salt...

TVCN track with IVCN intensity is 128 knots over SFL.

GFDL has a Cat 5 in the GOM

HWRF has a Cat 4 near Miami

..Oof

FULL IMAGE (Recommended)





this is going too be fun
Member Since: Posts: Comments:
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Levi,

I get the sense that with the models swinging to the right that some people seem to think Irene will swing off harmlessly away from the coast (that is a general feeling I'm getting) In your opinion what is the likelihood of that happening? Slim to none?
Member Since: Posts: Comments:
Quoting JrWeathermanFL:
I am 12. I have a few dreams. 1 of them weirdly, is that I wish for 5 great bloggers to comment on my post. I dunno why... Weather456 and TropicFreak and HurricaneDean have, bu I would love some others. I want to become the second Dr. Masters lol.
Well try and make your own weather site.AMAF you can start tonight or tomorrow.You can start your own blog to.People will probally eventually latch on to it.
Member Since: Posts: Comments:
Quoting Levi32:


I bet you do.


her mother is an old friend of mine...and if you keep talkin' about South Carolina...I may need to go visit them...
Member Since: Posts: Comments:
Quoting Levi32:
The 12z CMC doom solution also has the same hole that the JMA has. Look at where it has it tomorrow morning - way too far south.

Earlier you said the tracks had it moving wsw in 12-18 hours. Maybe it was not actually moving wsw but rather relocating/reforming a center wsw. Is this possibly what they saw ?
Member Since: Posts: Comments:
Grain of salt...

TVCN track with IVCN intensity is 128 knots over SFL.

GFDL has a Cat 5 in the GOM

HWRF has a Cat 4 near Miami

..Oof

FULL IMAGE (Recommended)

Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Ahhh, that makes more sense. Not much of a shift then.


The other one made no sense with the GFDL out in the Yucatan channel and the track shifted east?
Member Since: Posts: Comments:
Good Evening. Now is the time for everyone from the Gulf Coast to the East coast to review your hurricane plan as mentioned by Dr. M. Between "re-formation" after passing Haiti and the timing of the trof, it could potentially swing anywhere between the Gulf to the East Coast because of the angle of approach once it exits North of Cuba and Haiti. Obviously, folks in extreme South Florida and the Keys are going to have very short notice if it heads towards them and a little longer for folks along the Eastern Gulf or East Coast (and also more time to re-strengthen the more it stays over water after the Florida Straits). It's a very tough long-term forecast as to both landfall and intensity because of all the variables so everyone in the cone (not down the center line) needs to be prepared to take action if needed.
Member Since: Posts: Comments:
And last but not least, the UKMET doom solution has the same problem.

Member Since: Posts: Comments:
I am rather puzzled as to just how far south the GFDL is. The models have been consistently predicting that the weakness would be farther east, which is what I still think also.
Member Since: Posts: Comments:
well that good news for land the mode runs keep this in the water longer makeing this a march stronger storm but at the same time bad new for the USA
Member Since: Posts: Comments:
Quoting WeatherNerdPR:

Which one is the most reliable?
I'd say the LGEM and DSHP in this case.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Well, the intensity guidance sure is all over the place:

Mmmm 145mph storm.Well the ships model always goes over board with intensity.
Member Since: Posts: Comments:
Quoting presslord:


I know a nice girl in Cold Bay


I bet you do.
Member Since: Posts: Comments:
Quoting nrtiwlnvragn:
As I suspected NHC updated Irene and the new TVCN


AL 09 2011082100 03 TVCN 0 150N 590W
AL 09 2011082100 03 TVCN 12 161N 627W
AL 09 2011082100 03 TVCN 24 168N 658W
AL 09 2011082100 03 TVCN 36 173N 683W
AL 09 2011082100 03 TVCN 48 180N 705W
AL 09 2011082100 03 TVCN 60 188N 727W
AL 09 2011082100 03 TVCN 72 195N 745W
AL 09 2011082100 03 TVCN 84 203N 763W
AL 09 2011082100 03 TVCN 96 214N 779W
AL 09 2011082100 03 TVCN 108 228N 793W
AL 09 2011082100 03 TVCN 120 245N 805W
AL 09 2011082100 03 TVCN 132 264N 817W
AL 09 2011082100 03 TVCN 144 295N 814W
AL 09 2011082100 03 TVCN 156 311N 830W
AL 09 2011082100 03 TVCN 168 326N 839W
Ahhh, that makes more sense. Not much of a shift then.
Member Since: Posts: Comments:
Quoting Levi32:
The 12z CMC doom solution also has the same hole that the JMA has. Look at where it has it tomorrow morning - way too far south.



Maybe it has the center reforming further south and west
Member Since: Posts: Comments:
Quoting ncstorm:


is this an east coast storm now?


Was just starting to feel like were in the clear for our area until that run. Although I noticed at the VERY end it looked like the model wanted to bend back NW into n Florida or Georgia. That ridge building back west may just may cut it off for us in NC
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Well, the intensity guidance sure is all over the place:


Which one is the most reliable?
Member Since: Posts: Comments:
Quoting Bluestorm5:
It had been renamed few hours ago. Hurricane Hunter ran into TS force winds and it had closed circulation.


Ya i know i typed the wrong number......check out the graphic off the Coast of Africa was what i was referring too.......Sorry
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting washingaway:
notice, not a northeast turn, in fact after turning north a bend back towards the west. Interesting.
Member Since: Posts: Comments:
I am 12. I have a few dreams. 1 of them weirdly, is that I wish for 5 great bloggers to comment on my post. I dunno why... Weather456 and TropicFreak and HurricaneDean have, bu I would love some others. I want to become the second Dr. Masters lol.
Member Since: Posts: Comments:


Member Since: Posts: Comments:
Quoting Patrap:

Dam burst!
Member Since: Posts: Comments:
Well, the intensity guidance sure is all over the place:

Member Since: Posts: Comments:

Viewing: 371 - 321

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74Blog Index

Top of Page

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.