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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3121. unf97
Quoting aquak9:
YO UNF!!! :) hi scooster

I am on the back porch, three miles inland from JaxBeach. Absolutely GORGEOUS day here, so still, even the willows are not moving. No Way can the weather deteriorate EVER, it's a perfect dream.


It is a beautiful morning here in the river city. Aquak, we may be dealing with something totally opposite of what we are experiencing currently by late Friday into Saturday though. It's going to be an interesting week to say the least.
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Quoting kmanislander:


Have to watch for those mountains !
Lol, that never crossed my mind. They were moving through western Basse-Terre over a volcanic relief during the momentary climb. Already back down to the regular height:

123400 1551N 06123W 8426 01586 //// 174 //// 184022 022 012 002 01
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Quoting aquak9:
YO UNF!!! :) hi scooster

I am on the back porch, three miles inland from JaxBeach. Absolutely GORGEOUS day here, so still, even the willows are not moving. No Way can the weather deteriorate EVER, it's a perfect dream.
I'm just an hour west of you, out here in da woods.
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GOES East in Rapid Scan Operations (8 images/hour)
loop


Mornin SJ, seems this year the HH have had more than normal equipment problems.
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3116. aquak9
Wart, where are you? Folks are supposed to put thier location in when they become members, I think, but many people just leave it blank.
Member Since: August 13, 2005 Posts: 165 Comments: 25910
Quoting barotropic:


Did u see the new GFDL run?



Yes i did.........Big Shift EAST.
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3113. HCW
Irene Hates FL 6z Models


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Latest Crown Weather Discussion:

Link
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Quoting StormJunkie:


They don't get along with props, wings, and fuses too well.


With the updrafts and downdrafts they will maintain a healthy margin above the island terrain out there.
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Morning All. Didn't like this comment from the NHC.

ONCE OVER THE FLORIDA STRAITS...HOWEVER...
IRENE WILL HAVE AT LEAST 24 HOURS OVER SOME OF THE WARMEST WATER IN
THE ATLANTIC TO TAP INTO. THE OFFICIAL FORECAST REMAINS ON THE
CONSERVATIVE SIDE DUE TO LAND EFFECTS AND IS CLOSE TO A BLEND OF
SHIPS AND LGEM STATISTICAL INTENSITY MODELS.


Still pretty rock solid, especially now with the GFDL swinging around.
Member Since: August 19, 2005 Posts: 5 Comments: 5395
41mph at the vortex message. It's no mystery where the strongest winds are, though:
Member Since: July 7, 2010 Posts: 0 Comments: 5682
Quoting bocahurricane:


I believe Wilma maintained or gained strength while crossing the everglades too. She came in gulf side and exited the east coast

That's exactly what happened with Wilma.
After her storm surge flooded 1/3 of the island of Key West, Wilma jaunted over to Miami/Fort Lauderdale, keeping and even gaining strength from the warm Everglades waters. A buddy of mine in Ft L lost electricity for 2 WEEKS after she hit! 1000's of vehicles in key west were destroyed and many homes had 5 feet of water in them
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Wonder what happens if Irene decides to pump the ridge?

lmao
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NOAA's two hi-res models have both sides of the FL peninsula covered, GFDL west and HWRF east...

Something is a LITTLE BIT OFF though with the way these models are handling land interaction. The GFDL has Irene over land spending a huge amount of time over Hispaniola and Cuba and yet maintains hurricane intensity.

I understand that Irene is quite a large circulation so will be more resistant to land influences and the divergence aloft will be great, but come on...
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3105. bwi
Good morning. Looks like the vortex message is 16.8 62.4 at 1006mb.

Seems to me that means we should get some west winds at buoy 42060 as it passes to the north (buoy is at 16.3 63.5). However, right now, winds at the buoy are NNE and pretty steady, with pressure of 1010.
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Not to change from Irene, but are there any T- waves or anything to watch for development in the next few weeks?
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3102. aquak9
YO UNF!!! :) hi scooster

I am on the back porch, three miles inland from JaxBeach. Absolutely GORGEOUS day here, so still, even the willows are not moving. No Way can the weather deteriorate EVER, it's a perfect dream.
Member Since: August 13, 2005 Posts: 165 Comments: 25910
Quoting aquak9:
Hiya wart- please call me aqua- cinn pizza, really just a huge flat cinn roll.
Twiddling my thumbs, looking south, seeing the line of the Cone'o'Doom trying to head this way.


You got it, aqua. And I know we probably go through that every year... while my brain shrinks more in size. ;-)

It's gorgeous here, bright and sunny. I'm waiting for the ants to starting building ladders to higher ground.
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Quoting TampaSpin:
Just too let everyone know but, i took off the password protection off my site........so everyone can view IRENE........i don't won't people not to have the ability to view every model and Graphic when they need.


What is your sites name. TIA
Member Since: July 27, 2008 Posts: 0 Comments: 108
3099. MZT
Quoting bocahurricane:


I believe Wilma maintained or gained strength while crossing the everglades too. She came in gulf side and exited the east coast
You're probably thinking of Fay. Wilma was more famous for having a stronger "backside" than forward side when she crossed.
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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 21st day of the month at 12:28Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 300)
Storm Number & Year: 09L in 2011
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 02
A. Time of Center Fix: 21st day of the month at 12:08:00Z
B. Center Fix Coordinates: 16°46'N 62°22'W (16.7667N 62.3667W)
B. Center Fix Location: 10 miles (16 km) between the W and WNW (281°) from Salem, Montserrat.
C. Minimum Height at Standard Level: 1,477m (4,846ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 36kts (~ 41.4mph)
E. Location of the Estimated Maximum Surface Wind: 33 nautical miles (38 statute miles) to the WNW/NW (304°) of center fix
F. Maximum Flight Level Wind Inbound: From 43° at 43kts (From the NE at ~ 49.5mph)
G. Location of Maximum Flight Level Wind Inbound: 43 nautical miles (49 statute miles) to the NW (307°) of center fix
H. Minimum Sea Level Pressure: 1006mb (29.71 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 16°C (61°F) at a pressure alt. of 1,529m (5,016ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 17°C (63°F) at a pressure alt. of 1,524m (5,000ft)
K. Dewpoint Temp & Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Levels (sfc and flt lvl centers are within 5nm of each other): Surface and 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 3 nautical miles
Remarks Section:
Maximum Flight Level Wind: 43kts (~ 49.5mph) in the northwest quadrant at 11:48:0
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Quoting kmanislander:


Have to watch for those mountains !


They don't get along with props, wings, and fuses too well.
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3096. tbrett
Quoting hurricanehunter27:
I wonder if the volcano will spew ash into the storm.


BITE YOUR TONGUE LOL..There will be no ash spewing at all!!!!!
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3095. scott39
Goodmorning everyone, something to ponder......... Irene reminds me of a much bigger and healthier version of Don and Emily. The track entering the E Caribbean is almost matching up for each storm. The BIGGEST difference is that Irene is already a developed TC, but not the best one at the moment. Here is the MILLION DOLLAR Question for me? Which High pressure steering system.....rate of speed.....and the breaking down of the ridge, does Irene compare the closest to, out of both Don and Emily?
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Quoting MiamiHurricanes09:
Just ascended a couple hundred feet. Hmmm...

122400 1613N 06146W 7816 02211 //// +140 //// 199020 021 /// /// 05


Have to watch for those mountains !
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Getting gusty as this approaches:
Member Since: July 7, 2010 Posts: 0 Comments: 5682
Quoting aquak9:
Good morning all. Leftover cinnamon pizza for breakfast- it's a little stale, but dips well in coffee. Help yourself, it's better toasted.

Anyone wanna guess if this'll be a huge rainmaker for FL, or maybe not so much?
I think I will go for the Cinnamon Toast Crunch :)
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Quoting hurricanehunter27:
I wonder if the volcano will spew ash into the storm.

How the volcanic ash influences the storm?
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3090. aquak9
Hiya wart- please call me aqua- cinn pizza, really just a huge flat cinn roll.
Twiddling my thumbs, looking south, seeing the line of the Cone'o'Doom trying to head this way.
Member Since: August 13, 2005 Posts: 165 Comments: 25910
000
URNT12 KNHC 211228
VORTEX DATA MESSAGE AL092011
A. 21/12:08:00Z
B. 16 deg 46 min N
062 deg 22 min W

C. 850 mb 1477 m
D. 36 kt
E. 304 deg 33 nm
F. 043 deg 43 kt
G. 307 deg 43 nm
H. 1006 mb
I. 16 C / 1529 m
J. 17 C / 1524 m
K. NA / NA
L. NA
M. NA
N. 1345 / 08
O. 0.02 / 3 nm
P. AF300 0209A IRENE OB 02
MAX FL WIND 43 KT NW QUAD 11:48:00Z
;
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hard to believe but tropical birds have been known to fly in the eye of these systems for hundreds of miles
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Time: 12:02:00Z
Coordinates: 16.75N 62.3333W
Acft. Static Air Press: 843.0 mb (~ 24.89 inHg)
Acft. Geopotential Hgt: 1,547 meters (~ 5,075 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 239° at 5 knots (From the WSW at ~ 5.8 mph)
Air Temp: 16.4°C* (~ 61.5°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 6 knots (~ 6.9 mph)
SFMR Peak (10s) Sfc. Wind: 22 knots (~ 25.3 mph)
SFMR Rain Rate: 6 mm/hr (~ 0.24 in/hr)
(*) Denotes suspect data

recon approaching
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Quoting aquak9:
Good morning all. Leftover cinnamon pizza for breakfast- it's a little stale, but dips well in coffee. Help yourself, it's better toasted.

Anyone wanna guess if this'll be a huge rainmaker for FL, or maybe not so much?

Good morning.
Member Since: July 7, 2010 Posts: 0 Comments: 5682
Quoting scooster67:


Stretch......Yawn......sniff..sniff..

Aqua,

Whats for breakfast?


Repost!
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Quoting stormwatcherCI:
Which is expected when you look at the steering layer. I said this earlier this morning and when you look at the loop you posted you can definitely see it.
,not suprising at all i mentioned a west or wsw turn about 6 hrs ago,right on time,expect very little northerly component for atleast 24hrs imo...charley pt 2,hope it s not a larger storm ,could change west coast of fl if a major rides the west coast
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3083. unf97
Quoting aquak9:
Good morning all. Leftover cinnamon pizza for breakfast- it's a little stale, but dips well in coffee. Help yourself, it's better toasted.

Anyone wanna guess if this'll be a huge rainmaker for FL, or maybe not so much?


Good morning aquak!
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Quoting TampaSpin:
Just too let everyone know but, i took off the password protection off my site........so everyone can view IRENE........i don't won't people not to have the ability to view every model and Graphic when they need.


Did u see the new GFDL run?
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting tbrett:


LOL yeah you did..it is Montserrat..
Could hear the HH plane about 15 mins ago..We have no wind and very little rain. we I am at 16.75N, 62.23W
I wonder if the volcano will spew ash into the storm.
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Quoting aislinnpaps:
HH say the enter of Irene appears to be over Monsaurat, which I just butchered in spelling.

WAIT
what?
Member Since: July 7, 2010 Posts: 0 Comments: 5682
Quoting alvarig1263:


Yes that was Katrina. Came ashore the FL east coast as a TS, came off the west coast south of Naples, FL as a Cat. 1.

Katrina Path


I believe Wilma maintained or gained strength while crossing the everglades too. She came in gulf side and exited the east coast
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Quoting aquak9:
Good morning all. Leftover cinnamon pizza for breakfast- it's a little stale, but dips well in coffee. Help yourself, it's better toasted.

Anyone wanna guess if this'll be a huge rainmaker for FL, or maybe not so much?



aquak! How the heck are you? Cinnamon pizza?


If I had to guess at this stage, big rain in Florida.
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Quoting bocahurricane:


Its beautiful there, we used to have a villa in dorado. enjoy your vacation and stay safe


Get those shutters figured out bocahurricane?
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting MiamiHurricanes09:
Just ascended a couple hundred feet. Hmmm...

122400 1613N 06146W 7816 02211 //// +140 //// 199020 021 /// /// 05

Maybe they noticed something?
Member Since: July 7, 2010 Posts: 0 Comments: 5682
Quoting osuwxguynew:
Looks like the recon center fix is around 16.76N 62.38W.


ATCF (incomplete) update agrees:

AL, 09, 2011082112, , BEST, 0, 168N, 624W, 45, 1005, TS, 34, NEQ, 130, 0, 0, 80,
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Just ascended a couple hundred feet. Hmmm...

122400 1613N 06146W 7816 02211 //// +140 //// 199020 021 /// /// 05
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Just too let everyone know but, i took off the password protection off my site........so everyone can view IRENE........i don't won't people not to have the ability to view every model and Graphic when they need.
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Quoting HurricaneSwirl:
FWIW, the TWC personally thinks it will go right in between Miami and Naples. They never actually said this, I was just looking at the wind directions in south florida's local forecasts. It sorta seems like it exits into the eastern GOM around Tampa but it's hard to be exact going off of these windshifts.


That's not good. Really not good.
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Quoting Culterbayor:
Here in Dorado Puerto Rico on vacation. Go fiqure storm warnings are going to follow me all the way home to Miami. Puerto Rico has a "not a big deal perspective on storms". Resort is good to go with back up generators and lots of free coffee...


Its beautiful there, we used to have a villa in dorado. enjoy your vacation and stay safe
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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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