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 DontAnnoyMe:


That's it - you need a blog, but not necessarily an entry in it.

Bingo.
Member Since: July 7, 2010 Posts: 0 Comments: 5684
Quoting MoltenIce:
Am I in 4chan or something?


>4chan
>not 2D porn

Nope. We're definitely not in 4chan.
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Check this out... it shows the eye of Irene passing over Key Largo, Florida at 11pm, August 25th, 2011... and then drastically picks up in winds with a change of direction. Found this really cool.



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Quoting DontAnnoyMe:


Go to the top of the page, hover over your handle, choose My Blog

I just checked it. Been so long I completely forgot.
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Quoting WeatherNerdPR:

I never posted a blog entry. but I do have a blog.


That's it - you need a blog, but not necessarily an entry in it.
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Quoting washingtonian115:
I hope that if the storm comes you still manage to get out of harms way. and keep your family safe.



I appreciate your concern. We'll be fine here, just worried about others that come to mind.
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Quoting SouthDadeNative:
It will be interesting to see how the new bridge over JewFish Creek affects northbound during the evacuation


What makes you so sure there will be an evacuation?
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Quoting GTcooliebai:
Correct me if I'm wrong here, but look at the streamline nosing it's way into Georgia, that would be your dip in the jet stream, that would induce a more poleward movement, so I don't know why the GFDL continues moving this west.



Cuz it's moving over 20mph to the west right now
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Quoting MississippiWx:


We aren't tied with 2005.
2011 is running close though.It's totally leaving 2010 in the dust.
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Quoting weatherguy03:


UKMET model is right up there with the GFDL model and in the long range was one of our best models last season.


I stand corrected, still the GFS and ECMWF is where I would put my money (nice chart by the way), but it's way too early to pinpoint the track, although I am starting to get spooked.
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The GFS has it near the west coast of Florida with virtually no shear involved..Link
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Wife says its time for some DQ icecream.........BBL!
Member Since: September 2, 2007 Posts: 178 Comments: 20439
608. unf97
Quoting Levi32:


Exactly. A nearly straight north path for a good ways is likely.


Good evening! Yeah, this scenario would be similar to Hurricane David if that happened Levi.

This is goinmg to be a nerve-wracking next 5-6 days tracking Irene. It is rather apparent that the Florida peninsula will likely be impacted directly or indirectly late this week by this system.
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Quoting stormwatcherCI:
LOL. What did I post ?


Go to the top of the page, hover over your handle, choose My Blog

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Quoting GTcooliebai:
Correct me if I'm wrong here, but look at the streamline nosing it's way into Georgia, that would be your dip in the jet stream, that would induce a more poleward movement, so I don't know why the GFDL continues moving this west.



It's pumping the ridge on the GFDL...lol.
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Quoting Relix:
I honestly believe that Emily's center is further North than expected.
do you mean Irene?
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Quoting MississippiWx:


Well, I have no idea then.

I never posted a blog entry. but I do have a blog.
Member Since: July 7, 2010 Posts: 0 Comments: 5684
Correct me if I'm wrong here, but look at the streamline nosing it's way into Georgia, that would be your dip in the jet stream, that would induce a more poleward movement, so I don't know why the GFDL continues moving this west.

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Quoting Bluestorm5:
Why is my ignored list button NOT WORKING?


for some reason, you may have to hit the update ignore list button twice.
After the first time you will see that the new name is not added,
then you hit the "back" arrow in your browser to make the name appear,
then hit the ignore user button and it works the second time.

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The waves are lining up over africa.The models while showing Irene also show two other lows out in the Atlantic.
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Need to take a break........Be back later..... :(
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Quoting DontAnnoyMe:


You do have a blog.
LOL. What did I post ?
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Quoting Huracaneer:
Only the GFDL and the UKMET has Irene going in the Gulf. While normally the GFDL is a good model, none of the previous runs developed 97L, so I won't take it seriously unless the next run is consistent. The UKMET is not one of the best models. Like Levi says "we shall see". However, I am (in live in the Tampa Bay Area) starting to gather my supplies and looking over my plans, just in case.


UKMET model is right up there with the GFDL model and in the long range was one of our best models last season.

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Quoting HurricaneDean07:
For the next two days, we will be officially tied with 2005... impressive beginning of the season that's for sure, even if they all stayed below Hurricane status, Irene will be the bust of the record(likely)


We aren't tied with 2005.

Edit: Nevermind, I see what you meant.
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Quoting Levi32:


At 892mb in the keys I would believe 200mph easily.


It's always at the top of any list of worst hurricanes or weather events so that seems about right...
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PUERTO RICO under a Tropical Storm Warning. Well i hope i don't wake up and see a hurricane as a good morning present and it moving closer to the island if that's happens well i will just hide under the bed.
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The new radar image from martinique shows that precip has formed a donut around what might become the eye, as of the 1:30z update (which was 4 minutes ago).

Click link below, and then click on "Animate" to see a loop of 4 image:

http://www.meteo.fr/temps/domtom/antilles/pack-pu blic/animation/animMOSAIC2.html
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Quoting NavarreMark:


Did ya honestly have to tell these folks that? They're almost besides themselves right now.
What ?
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Quoting MoltenIce:
Am I in 4chan or something?

XD
Member Since: July 7, 2010 Posts: 0 Comments: 5684
Quoting stormwatcherCI:
Not true. I have never made a blog post and can ignore someone.


Well, I have no idea then.
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Hitting the report key is a good idea, it's totally inappropriate.....but just out of curiousity....is there anybody here who's put you know who on ignore?
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For the next two days, we will be officially tied with 2005... impressive beginning of the season that's for sure, even if they all stayed below Hurricane status, Irene will be the bust of the record(likely)
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586. Relix
I honestly believe that Emily's center is further North than expected.
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Quoting stormwatcherCI:
Not true. I have never made a blog post and can ignore someone.


You do have a blog.
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Quoting StratoCumulus:


1970 right, good music...!
Ooooh yeah!!!.And 80's music.The 80's were some of the best years of my life.I still remember the huge colorful bows being popular.
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Quoting Levi32:
Gotta run now. Back in the morning.
Thanks for sharing your insights with us Levi :)
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Quoting MoltenIce:
Am I in 4chan or something?


LOL
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Yes, I was advised today to be sure to have my Keys resident sticker as I work in the mainland (Fort Lauderdale) and will not be able to get back down here to my home after Tuesday (or when evacuations begin). I just got my home down here in May and my family stays here while I am up in Lauderdale 4 days out of the week for work.


Quoting Thrawst:


Nassau, Bahamas here.. although I believe you are more at risk than me, get prepared ahead of time!
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Quoting MississippiWx:


Have you made a blog post? I don't think you can ignore anyone until your blog is activated.
Not true. I have never made a blog post and can ignore someone.
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It wasn't JFV- he DOES NOT KNOW how to post a pic. Never has, never will.

Back to topic.
Member Since: August 13, 2005 Posts: 166 Comments: 25940
Quoting DontAnnoyMe:


You have to make a blog entry first, for it to work.
sigh, I'm going to make short blog... I was hoping I'll learn more before making first blog.
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Am I in 4chan or something?
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Quoting WeatherNerdPR:

LOL


LOL!!
Member Since: August 22, 2010 Posts: 0 Comments: 652
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Taz and Levi Im thing a earl like track up the east coast maybe a little farther west than earl, discounting that earn never made it into the carrib but, what im trying to say is it IMHO will brush the conus and hit somewhere between long island and nova scotia
Member Since: July 27, 2008 Posts: 0 Comments: 108
Quoting Bluestorm5:
whew, I think JFV is gone. Seriously, why my ignored button not working?

Anyway, when the next recon plane heading out?
Tomorrow morning around 8 am EDT.
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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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