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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Quoting RitaEvac:
Tanks in the Yucatan channel, if this were to pan out, this would be the storm of the year, and expect oil prices to go off the chart


oil prices wouldnt go up to much half of our oil isnt even from the US
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Quoting P451:
Pretty far north:

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Thanks Dr Masters, for your timely blog post. It's truly a watch and wait scenario for us in South Florida. Prepare if you haven't already, if you have prepared, just wait until it's time to implement your plans. I have feeling we're all going to have some heartburn and headaches with this storm. Right now I wish all those in the islands about to meet Irene luck and minimal effects.
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Quoting Tazmanian:
poll when will we get too 2,000 commet


A 6pm


B 10pm


C 11pm

D 12AM

e probably around midnight-2 am
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Quoting 3211976:
how can i post a picture from my files


You would have to upload it first on a image hosting site if you would like to post a picture on the blog.
Member Since: June 21, 2010 Posts: 0 Comments: 528
Quoting daddyjames:


Loks like the husband is going to have a loong night . . .


I wouldnt put the shutters up, nor would I cancel the trip. I would be a little patient and see what the NHC says and the models say the next couple runs. I would start to watch them more carefully tomorrow. It may be a tough call as if infact Irene goes over land toward S Florida, the intensity forecast may be somewhat of a coin toss.
Member Since: August 22, 2010 Posts: 0 Comments: 652
163. amd
Quoting SouthDadeFish:
Latest wind shear analysis shows the anticyclone slowly migrating towards the deeper convection, which makes a lot of sense when you think about all the heat being released there.



I'm think either convection will build more over the center tonight or we'll see the MLC pull in the LLC.


I'll go with option number 1. Looks like the stuff to the west and southwest of Irene is weakening and moving faster than Irene right now, and once that is out of the picture in a few hours, I suspect some convection will form to the south of the center. IMHO
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Tanks in the Yucatan channel, if this were to pan out, this would be the storm of the year, and expect oil prices to go off the chart

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Quoting daddyjames:


Loks like the husband is going to have a loong night . . .


Yeah he is. I don't even know if I could do it in 2 days. I am 5 feet, 100lbs. Not much strength here. HAHA
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how can i post a picture from my files
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Quoting P451:


That's the mid-level center.
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poll when will we get too 2,000 commet


A 6pm


B 10pm


C 11pm

D 12AM
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Does anyone have the dominica radar loop link?
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Quoting jennT:
in st. croix: have vaccuumed, dishes, saved and refilled ice trays, have water, gas and food--now we wait to see what she brings.


Stay safe. Best of luck.
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Quoting P451:




Same place I was thinking, Irene still organizing!
Member Since: April 29, 2007 Posts: 0 Comments: 7862
Keeper as always with the sound advice.
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Quoting HoustonTxGal:
What on earth do we have to do here in TX to get some rain? We need a Tropical Storm here bad to drop a few days worth of the wet stuff on us.


I know right! We don't need another Ike though. Just a nice slow drenching TS would be nice.
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Experimental FIM model:Link
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Quoting KennyNebraska:


Could you please repost this picture and spotlight where you say the center is. There are those of us that do not clearly see the center.

In my case, I see tree leaves flying through the air. Someone else might be seeing lasagna.


It's somewhere in here:

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Wait and see as always.
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Quoting bocahurricane:
Hey everyone, I have been on this site for years mostly as a lurker. I have a question for some of experts on here. Normally I wouldnt be at that worried but I live in Palm Beach County and my husband is heading out of town on business tomorrow and won't be back till Friday. I have 2 kids (ages 1 and 3). I have a 6 bedroom 2 story house that will take me at least 2 days to shutter if I can't find someone to hire and do it for me. How concerned should I be and when do you think we are going to have a better idea exactly where, when and strength?


best advice

wait watch see

follow advice from NHC/TPC on forecasts and local state officials for your health and safety concearns

as for protecting property one should begin preps at least 72 hrs before landfall of a forecasted event more if so needed

and prpare a basic emerg kit for at least 72 hrs after event

Weather Safety Emergency Checklist
Be ready for a weather emergency in advance and put together a basic survival kit.

Food Items:
Bottled drinking water
Bread
Crackers
Cookies, snacks
Canned fruit
Canned meat, fish
Apples, bananas
Dried fruit
Canned/boxed beverages
Fruit drinks
Peanut butter

Non-Food Items:
Ice
Coolers
Plastic forks and cups
Napkins
Can opener (non-electric)
Batteries for flashlights and radio
Plastic trash bags
Charcoal
Water purifying tablets
Flashlights
Candles and matches
Clothing and bedding
Extra socks and underwear
Pillows
Sleeping bag and blankets
Washcloth and towel for each person
Soap, toothbrushes, toothpaste
Deodorant
Shaving kit
Contact lens solution
Hair care items and mirror
Dentures
Sanitary napkins and tampons
Paper towels, toilet paper
Hearing aid batteries
Watch or clock
Portable radio with fresh batteries
Chlorine tablets
Spare pair of eyeglasses
Cash
Prescription medicines
Important papers (drivers licenses, insurance policies, social security cards)
Toolbox with hammer, nails, screws, screwdrivers and wrenches (to use after the storm to make your home livable again)
Cell phone (take an extra battery or a means to power or charge it)
list of people to contact for emergencies

First Aid Kit:
Keep contents of first aid kit in a waterproof metal or plastic box.

Prescription medicines (four-week supply)
Bandages and Band-Aids
Antiseptic
Adhesive tape rolls
Aspirin
Sun-screen
Insect repellent
First aid handbook
Scissors
Antibacterial soap
Safety pins
Thermometer
Needle (for splinters)
Items for Infants:

Small toys include favorite stuffed animals
Clothes
Diapers and baby wipes
Milk or formula
Powders, creams or ointments
Bottles and nipples
Baby food
Sheets, blankets, rubber pads
Portable crib
Plastic bags
Pacifiers
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Quoting MiamiHurricanes09:
Indeed. Would mean the circulation is near 15.5˚N then.




09 what you make of this


20/2345 UTC 15.3N 58.8W T2.0/2.0 IRENE -- Atlantic
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Quoting bocahurricane:
Hey everyone, I have been on this site for years mostly as a lurker. I have a question for some of experts on here. Normally I wouldnt be at that worried but I live in Palm Beach County and my husband is heading out of town on business tomorrow and won't be back till Friday. I have 2 kids (ages 1 and 3). I have a 6 bedroom 2 story house that will take me at least 2 days to shutter if I can't find someone to hire and do it for me. How concerned should I be and when do you think we are going to have a better idea exactly where, when and strength?


I'd be reasonably concerned. We should have a better idea of where Irene ultimately ends up over the next two or so days. Her trajectory depends not only on how quickly she intensifies, but also what shape she is in after impacting the Greater Antilles. Not to mention, the track could easily shift further west or east depending on distinct but important changes in the pattern.
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Quoting HoustonTxGal:
What on earth do we have to do here in TX to get some rain? We need a Tropical Storm here bad to drop a few days worth of the wet stuff on us.


My Dear. As far as I'm concerned, You can have every drop of this system.
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142. JLPR2
Quoting P451:




NW of there according to the Martinique radar.
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I hope that Irene doesnt ride the whole state of Fl as a hurricane or tropical storm.
Member Since: June 13, 2009 Posts: 0 Comments: 6784
So much dry air I would be surpised if Irene ever reaches Hurricane Status. This year has too much dry air that anything forming can't really get its act together.
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138. A4Guy
Dr. M talks about the dry air...but it seems like Irene did a pretty good job moistening her environment with the storms she threw off today.
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Quoting spathy:


Not analog storm.
Early modeling that ends up in almost the same landfall area.


ooops my bad :D
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P451...

Why is it that when I look at that avatar and read your posts I read them in a loud, screaming voice?

(Freakin love that avatar and when the school kids get on here with a Florida cone, it's gonna be very, very appropriate!)
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Latest wind shear analysis shows the anticyclone slowly migrating towards the deeper convection, which makes a lot of sense when you think about all the heat being released there.



I'm think either convection will build more over the center tonight or we'll see the MLC pull in the LLC.
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Quoting JrWeathermanFL:
More polls:

What will Irene peak at?
A.50-70mph
B.75-105mph
C.110-130mph
D.135-165mph
E.170+

Will Gert emerge over the BOC?
A.Yes
B.No

What will 98L peak at?
A.Invest
B.TS
C.Hurricane
D.Major Hurricane

If we get to the Greek names, how far do you think we'll get?
A.1st name-4th name
B.5th name or more


1. F. Doom
2. (Harvey, not Gert) Answer: Who cares? TX does!
3. E. Doom
4. C. Omega
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Quoting Levi32:
Center is clearly visible on Antilles radar due east of Dominica.

Indeed. Would mean the circulation is near 15.5N then.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting naplesdreamer28:
Is it me or do the models seem to be pretty well in agreement on this one? Im in SW FL and don't like to see that. I've seen models that go over us and then hours later are totally different, but this one they seem to just pinpoint Florida. ?
I agree Sw Florida seems to be a target. As fast as irene is currently moving, she will have to trend more wnw in the next 12-24 hours before a southeast us coast landfall seems less likely. If it doesn't start a slight northward component soon, it will have a hard time going north of the mountainous islands... In turn, passing over the islands will weaken the system and make the SE us coast solution even less likely.

Just my two cents, but I feel the next day is critical in helping us figure out her future path
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130. jennT
in st. croix: have vaccuumed, dishes, saved and refilled ice trays, have water, gas and food--now we wait to see how long the power is out.

update: have heard some thunder rumbling around...
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20/2345 UTC 15.3N 58.8W T2.0/2.0 IRENE -- Atlantic
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Quoting JrWeathermanFL:
More polls:

What will Irene peak at?
A.50-70mph
B.75-105mph
C.110-130mph
D.135-165mph
E.170+

Will Gert emerge over the BOC?
A.Yes
B.No

What will 98L peak at?
A.Invest
B.TS
C.Hurricane
D.Major Hurricane

If we get to the Greek names, how far do you think we'll get?
A.1st name-4th name
B.5th name or more
Member Since: June 21, 2010 Posts: 0 Comments: 528
Quoting bocahurricane:
Hey everyone, I have been on this site for years mostly as a lurker. I have a question for some of experts on here. Normally I wouldnt be at that worried but I live in Palm Beach County and my husband is heading out of town on business tomorrow and won't be back till Friday. I have 2 kids (ages 1 and 3). I have a 6 bedroom 2 story house that will take me at least 2 days to shutter if I can't find someone to hire and do it for me. How concerned should I be and when do you think we are going to have a better idea exactly where, when and strength?


Loks like the husband is going to have a loong night . . .
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Quoting JrWeathermanFL:
More polls:

What will Irene peak at?
A.50-70mph
B.75-105mph
C.110-130mph
D.135-165mph
E.170+

Will Gert emerge over the BOC?
A.Yes
B.No

What will 98L peak at?
A.Invest
B.TS
C.Hurricane
D.Major Hurricane

If we get to the Greek names, how far do you think we'll get?
A.1st name-4th name
B.5th name or more



E
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Quoting Levi32:
Center is clearly visible on Antilles radar due east of Dominica.





hi levi u there, can u confirm that the LLC is removed from the deep convection and it cant intensify untill it slips under it
Member Since: July 21, 2010 Posts: 0 Comments: 1163
Quoting Levi32:
Center is clearly visible on Antilles radar due east of Dominica.



Could you please repost this picture and spotlight where you say the center is. There are those of us that do not clearly see the center.

In my case, I see tree leaves flying through the air. Someone else might be seeing lasagna.
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Quoting P451:


So, let's use one that's a little more realistic then.




Well, nah, that one is pretty scary too. Solid -75 to -82C blob. Look at how well the system consolidated in the past few hours. The baby fat is almost entirely gone.



It does look scary.
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Quoting P451:


So, let's use one that's a little more realistic then.




Well, nah, that one is pretty scary too. Solid -75 to -82C blob. Look at how well the system consolidated in the past few hours. The baby fat is almost entirely gone.



But there is almost nothing south of the center. May even be exposed.
Member Since: August 22, 2010 Posts: 0 Comments: 652

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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.