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: 471 - 421

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

Thanks for the encouragement guys!
Member Since: Posts: Comments:
Quoting Patrap:

dont know enough about anything -i would not be shocked if we have a cat 2 hurricane at 8 am advisory sun morning
Member Since: Posts: Comments:
Quoting InTheCone:


I just drove up 95 2 days ago with the thought of evac. in mind. If you don't leave VERY early, it ain't happening. Even in normal traffic, it was busy. Look locally, or leave early!


If I leave early, i'm taking 95. If not, i'm taking 441.
Member Since: Posts: Comments:
468. beell
Quoting KoritheMan:


The GFS has a ridge extending farther west than the Euro, yes, but a large enough weakness is still present so that Irene only impacts the eastern Gulf.

In other words, the GFS doesn't appear to be an outlier among the consensus.


That would be my guess this evening also.
Member Since: Posts: Comments:
T.C.F.W.
09L/TS/I/CX
MARK CENTRE FIX
16.63N/59.29W
Member Since: Posts: Comments:
454 Defentally so not cool.
Member Since: Posts: Comments:
It seems like the system is evacuating to fast in upper levels for such ill defined and broad low pressure at the surface.
Member Since: Posts: Comments:
Quoting ncstorm:


tornados this year havent been weak, we NC have had first experience..lets hope you are right if this scenario comes into play..


Tornadoes spawned by tropical systems are not the same as those that are formed by supercells. Not even close. I've seen it here in Central NC for many years. There may be some damage, but it will be minimal.
Member Since: Posts: Comments:
Quoting InTheCone:


Nasty, dirty picture! Evil old man, although I have a feeling that you are younger than me :)


No, I am just a little old, lonely man. Are you really in the Cone, or is your name just deceiving
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
you do know hurricanes can exceed 200 mph right strip the land of everything even life so that nothing remains not but the dirt and the water


Hearing reports and stories on the 1935 Labor Day storm some say 200+ mph winds...even have heard 250 mph gusts but I think that may be a little too high.
Member Since: Posts: Comments:
Quoting weatherguy03:
The focus for Irene's eventual U.S landfall continues to be Florida, and I still believe this will not change much. Could it be just West or just East of Florida?? Sure. But I believe the main impact will be across Florida and the Southeast Coast.


yea...it's kinda hard to come up with a scenario which doesn't include Florida...
Member Since: Posts: Comments:
Quoting TampaSpin:


WE BETTER HOPE THE GFDL IS WRONG......sorry for the Caps.

almost like an ivan path but then again ivan is in the past
Member Since: Posts: Comments:
Quoting weatherguy03:
The focus for Irene's eventual U.S landfall continues to be Florida, and I still believe this will not change much. Could it be just West or just East of Florida?? Sure. But I believe the main impact will be across Florida and the Southeast Coast.


I meant just East or West of the Florida Peninsula.
Member Since: Posts: Comments:
Quoting caneswatch:


It's worrying me too. I'm living in South Florida, and if Irene does become a Cat. 4 or 5, I'm heading north.


I think if it does head to s florida that it would have to go over to much land so a cat 4 or 5 is highly doubtful.
Member Since: Posts: Comments:
Quoting caneswatch:


It's worrying me too. I'm living in South Florida, and if Irene does become a Cat. 4 or 5, I'm heading north.


I just drove up 95 2 days ago with the thought of evac. in mind. If you don't leave VERY early, it ain't happening. Even in normal traffic, it was busy. Look locally, or leave early!
Member Since: Posts: Comments:
447. DFWjc
Quoting weatherjr:
I am not sure if some bloggers here hate or wish a tremendous hypercane headed to them.


I'm not liking the Cat 5 in the GOM, i don't care how drought-striken we are here in Texas...
Member Since: Posts: Comments:
Quoting DontAnnoyMe:


That's a typical scenario, if the remnants are going north and the center is west of the App. Mtns. However, those types of tornadoes are generally very weak and short-lived.


tornados this year havent been weak, we NC'ians have had first experience..lets hope you are right if this scenario comes into play..
Member Since: Posts: Comments:


WE BETTER HOPE THE GFDL IS WRONG......sorry for the Caps.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting GTcooliebai:
So the GFDL seems to be the outlier at the present time?


Unless we see the other models follow suit, yes. I would say so. Do you have any thoughts on that?
Member Since: Posts: Comments:
Quoting StratoCumulus:
I'm 41 and love weather and this wunderground site also, but stop writing nonsense posts about where a storm will go.
Enjoy reading and learning from Jeff, Tazmanian, Stormpetrol and Orcasystem.
I'm 41 also!!!.1970 to eh?.And @424 so not cool man.
Member Since: Posts: Comments:
Quoting stormhank:
Is it out of the realm of possibility that irene could follow the ukmet / gfdl track?? i read the updated discussion from crown weather that said irene could miss hispainola n do the gap between jamaica n cuba and then at the 120 hr point be very near key west


A track near Key West is still well within the realm of possibility, but I seriously feel the UKMET and GFDL are way too far south.
Member Since: Posts: Comments:
Quoting KoritheMan:


The GFS has a ridge extending farther west than the Euro, yes, but a large enough weakness is still present so that Irene only impacts the eastern Gulf.

In other words, the GFS doesn't appear to be an outlier among the consensus.
So the GFDL seems to be the outlier at the present time?
Member Since: Posts: Comments:
In mentioning the US coast, does Dr Masters include Texas?
Member Since: Posts: Comments:
Quoting AstroHurricane001:


Do you know what the actual weather factor was?


Post #419
Member Since: Posts: Comments:
Interesting storm, this one...

Member Since: Posts: Comments:
After some COC reformations, can we say that Irene is Stationary?
Member Since: Posts: Comments:
Quoting Bluestorm5:
As if April 14-16 wasn't enough... that EF3 tornado in Sanford almost killed my grandparents and another EF3 almost hit my town at I-40/I-95.


Unfortunately if I had to pick between a hurricane or a tornado, I would take the hurricane..at least you have more of a notice, tornados, probably about 30 minutes, top
Member Since: Posts: Comments:
The focus for Irene's eventual U.S landfall continues to be Florida, and I still believe this will not change much. Could it be just West or just East of Florida?? Sure. But I believe the main impact will be across Florida and the Southeast Coast.
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
you do know hurricanes can exceed 200 mph right strip the land of everything even life so that nothing remains not but the dirt and the water
Yeah.i was watching a story about hurricane Camille a few years ago on the discovery channel.I saw the photos.and absolutly nothing was left on the coast.Cars were buried in the sand and only foundations of houses stood.
Member Since: Posts: Comments:
Is it out of the realm of possibility that irene could follow the ukmet / gfdl track?? i read the updated discussion from crown weather that said irene could miss hispainola n do the gap between jamaica n cuba and then at the 120 hr point be very near key west
Member Since: Posts: Comments:
I'm 41 and love weather and this wunderground site also, but stop writing nonsense posts about where a storm will go.
Enjoy reading and learning from Jeff, Tazmanian, Stormpetrol and Orcasystem.
Member Since: Posts: Comments:
There has been no upwelling issues so far either in the Gulf or off the Florida Coast so water temps are very warm......Any length of time over water after Hispanola and low sheer will definitely come into play on the intensity models once they get a handle on track post-Greater Antilles.
Member Since: Posts: Comments:
Quoting Levi32:
We even have the NOGAPS going bonkers on intensity now despite land interaction all the way to Florida.


Oh boy, can I have the link to the NOGAPS? TIA :)
Member Since: Posts: Comments:
Quoting ncstorm:
Frank Strait of Accuweather said if this comes over west of Florida that NC/VA will have a decent outbreak of tornados..


That's a typical scenario, if the remnants are going north and the center is west of the App. Mtns. However, those types of tornadoes are generally very weak and short-lived.
Member Since: Posts: Comments:
Quoting BenBIogger:
Weather related accident.

Plane crash kills 12 in Canada's Arctic


Do you know what the actual weather factor was?
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Yup. Thursday landfall:



and keeps the same intensity riding up the east coast..
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)



OUCH!! not liking the Cat 5 entering the Gulf We need rainhere in TX but not that bad.
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
you do know hurricanes can exceed 200 mph right strip the land of everything even life so that nothing remains not but the dirt and the water


Wind over 200mph turns it into a Black hole Cane.... nothing escapes from it.... ;-)
Member Since: Posts: Comments:

Viewing: 471 - 421

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.

Local Weather

Overcast
27 °F
Overcast