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 AussieStorm:

Any idea what F that Tornado was? It's rare for Belize to have tornado's right?
lucky for you, I know alot about tornadoes. That storm haven't been rated yet, and you are correct, it's rare in Belize. I would say F-0 or F-1, but never judge how powerful tornado is by size. It look like F-3 to most people, but I think it was F-0 or F-1.
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Quoting barotropic:


A vortex data message just came in at 16.7. The center you are speaking of is mid level COC
There you have it!!

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Quoting barotropic:


A vortex data message just came in at 16.7. The center you are speaking of is mid level COC




so she not even verticly stacked yet
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3518. Gorty
Quoting flhurricanesurvivor:
on a few models it appears that the high retreats just enough for irene to skirt the east coast of florida before being pushed back to the se coast by the high building in again. does anyone else see this or am i reading it wrong. thanks


See, I have a hard time wrapping my head around that. Sure a few models shows that, but what if others does not? Which do we believe?
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Quoting Bluestorm5:
Is StormW's incident really that bad? Not going to push anyone into telling me the story.

Anyway, plane going over what should be where center is located.


Yes...

Now back to Irene. Haiti is about to get tons o rain; and we are not far away from finding out how well Irene can stomach 10k ft mountains.
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3516. ncstorm
Has anyone noticed that the bermuda is becoming in the bullseye in the ensemble members for 98L..trending west

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3515. scott39
Quoting StormJunkie:


The plane is currently at 17.15 N with due northerly winds...The center is not south of there imho. With that reading there shouldn't be anyway the center could be south of there.
Lets hope it keeps jumping N until its fish:)
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3514. wxhatt
Quoting HuracanTaino:
It seems more and more that she will cross Puerto Rico and head NW towards the Bahamas and SE Florida ...


That track could be worse...
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Quoting Ameister12:
Tornado spawned by TS Harvey in Crooked Tree Village, Belize.



:O
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3512. ackee
Quoting stormpetrol:
From what I can see the center has wobbled a tad south of due west over the last 2 hours, will be interesting to see the latest center fix soon to confirm
v agree
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3511. Grothar
Interesting how the GFDL and the HWRF switched their position from last night. Yes, I know these are old, new ones will be coming out which are different. This is not written in stone. Things could change. The HWRF is overdone. The GFDL just got on board. I don't believe it either.



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Quoting chrisdscane:
the center is at 17.5 not under 17 why would you say that


A vortex data message just came in at 16.7. The center you are speaking of is mid level COC
Member Since: August 22, 2010 Posts: 0 Comments: 652
3509. barbamz
Quoting Ameister12:
Tornado spawned by TS Harvey in Crooked Tree Village, Belize.



Frightning! Thanks for posting.
And here once again the webcam of St Barths (near the COC - edit: north of ...)
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3508. ncstorm
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3507. MZT
Quoting aasmith26:

Why was StormW banned? :(
The blog has always had a raucus side. I think he burned out defending his forecasts against junior bloggers. He started sniping back at people, and things degraded into "playground dynamics". (When children know you don't like to be taunted, they will keep doing it to watch your face turn red and see you stomp your feet.) He may have been "banned" but it was also kind of mutual. He needed his own space.
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Quoting wxhatt:
center of circulation showing up on Puerto Rico long range radar heading almost due west towards the southern shores of the island.



That center is MID COC. Clear on radar...all the way up at 17.3N
Member Since: August 22, 2010 Posts: 0 Comments: 652
the center is at 17.5 not under 17 why would you say that
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@3282

Anyone know what the UK model is picking up on that's sending it so much further west than the other models?
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Quoting cwf1069:
Good morning wunderblogers. It looks like a new center relocation further north. Plane found south wind north of 17. Also note that to the wind speed you have to add the speed motion on the ne quadrant of the storm and deduct from the nw side of the storm.


Yep, I meant south wind in my previous post...Think I said N by accident.
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jog to the North? The press in P.R said that the NWS on San Juan is on call conference with NHC to see if the watch will be changed to a hurricane warning to

giro hacia el norte? Las noticias locales en P.R dijeron que el SNM en San Juan se encuentra en conferencia con el CNH en Miami para ver si cambian la vigilancia a aviso de huracan.
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Quoting Ameister12:
Tornado spawned by TS Harvey in Crooked Tree Village, Belize.



Any idea what F that Tornado was? It's rare for Belize to have tornado's right?
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Quoting 900MB:


Right now the models are split between E Coast of Fla and W coast of Fla. If she keeps recentering North, expect the models to shift East from Miami to Jersey, but it's too early to call. We'll see what happens over the next 24 hours (obviously crucial).
It seems more and more that she will cross Puerto Rico and head NW towards the Bahamas and SE Florida ...
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Quoting clwstmchasr:


He joined Al Bundy as a shoe salesman.


Google him.
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center is trying to wrap up but hey... every hour i come back it looks better
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3497. wxhatt
center of circulation showing up on Puerto Rico long range radar heading almost due west towards the southern shores of the island.

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Is StormW's incident really that bad? Not going to push anyone into telling me the story.

Anyway, plane going over what should be where center is located.
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Quoting TampaCat5:
Someone yesterday posted an animation showing the models and forecast track for Ivan over the life of the storm which showed the dramatic shift to the west in the models. Anyone know where I can find this? Do they have them for all storms? Been googling with no luck. Would appreciate if you send me a message since this board is hard to keep up with.



I've seen many forecast cones shift from East of Florida to directly over Florida to West of Florida with an eventual landfall on the northern gulf coast.

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Quoting flhurricanesurvivor:
on a few models it appears that the high retreats just enough for irene to skirt the east coast of florida before being pushed back to the se coast by the high building in again. does anyone else see this or am i reading it wrong. thanks


This is a definite possibility. The angle of approach shown by the HWRF in the last couple of runs is extremely troubling to me- Irene follows the Gulfstream up the entire Florida Peninsula, intensifying all the way, then head for my neck of the woods.
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Quoting farhaonhebrew:
jog to the North? The press said that the NWS on San Juan is on a call conference with NHC to see if the hurricane watch will be changed to a hurricane warning to P.R
WHy they have not already is alarming!! The potential is there even though I feel it stays to the south. Surprised to see this.
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Quoting TampaCat5:
Someone yesterday posted an animation showing the models and forecast track for Ivan over the life of the storm which showed the dramatic shift to the west in the models. Anyone know where I can find this? Do they have them for all storms? Been googling with no luck. Would appreciate if you send me a message since this board is hard to keep up with.

Link
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3491. cwf1069
Good morning wunderblogers. It looks like a new center relocation further north. Plane found south wind north of 17. Also note that to the wind speed you have to add the speed motion on the ne quadrant of the storm and deduct from the nw side of the storm.
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Quoting farhaonhebrew:
jog to the North? The press said that the NWS on San Juan is on a call conference with NHC to see if the hurricane watch will be changed to a hurricane warning to P.R

Whoa, that'll cause chaos in the supermarkets.
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Quoting aquak9:

okay thanks vincent gotta run now gotta mop the floor and do 5 loads of laundry and mow and weedeat and board up the cat and duct tape the palm trees and yall stay safe and be safe and review your hurricane preparedness TIA ok thx bai

sure i just added caffeine because i wanted you to stay up all night i feel lonely when it's afternoon here while it's late night in your country
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3488. ncstorm
Good Morning..just waking up after hanging with the night shift last night watching Irene..I see the NHC got a hurricane affecting florida in the 5 day cone..
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Quoting stormwatcherCI:
Exactly my point. Not north of 17N as some are saying.


Irene is very poorly organised. People are sayin north of 17N because radar shows a real clear COC way up at 17.3. Surface COC is not even visible at all. Recon just fixed it at appx 16.6. System not stacked at all.
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting flhurricanesurvivor:
on a few models it appears that the high retreats just enough for irene to skirt the east coast of florida before being pushed back to the se coast by the high building in again. does anyone else see this or am i reading it wrong. thanks




isee were ur geeting it from but it'll be nearly impossible for this systam to not landfall in florida
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Quoting stormwatcherCI:
Exactly my point. Not north of 17N as some are saying.


The plane is currently at 17.15 N with due northerly winds...The center is not south of there imho. With that reading there shouldn't be anyway the center could be south of there.
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If South Florida stays in the cone of DOOM too much longer I'm gonna have to think about getting my shutters out of the corner of the garage. Which means I'll need to break out the Field Guide to Spiders.
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Someone yesterday posted an animation showing the models and forecast track for Ivan over the life of the storm which showed the dramatic shift to the west in the models. Anyone know where I can find this? Do they have them for all storms? Been googling with no luck. Would appreciate if you send me a message since this board is hard to keep up with.
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jog to the North? The press said that the NWS on San Juan is on a call conference with NHC to see if the hurricane watch will be changed to a hurricane warning to P.R
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3481. GetReal
<
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3480. WxLogic
12 NAM @24HR:

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3479. breald
Quoting sullivanweather:
Hello, Breald!

It feels great to be back here again! How have you been?

I'm really glad to see some of the regulars are still here. Lots of newbies, though.


Yeah we missed you last winter! Yes lots of newbies, but many of the regulars still blog. I haven't been on much myself.
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on a few models it appears that the high retreats just enough for irene to skirt the east coast of florida before being pushed back to the se coast by the high building in again. does anyone else see this or am i reading it wrong. thanks
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16 deg 46 min N

062 deg 22 min W

When you have longitude or latitude expressed in 'minutes' think of real minutes, as in 60 in an hour, or in this case - 60 in one degree.

So '16 degrees 46 minutes N' would be 16.77°N
'062 deg 22 minutes W' would be 62.37°W
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Quoting Abacosurf:


If you watch the overall trends on the visible loop with lat/long you can see it riding along the 17 or .1 or.2 below.

The high is obviously strong due to the fast forward speed as Kman and others have pointed out.

I do not see this going north of hisp.

Have to follow the trends.
Exactly my point. Not north of 17N as some are saying.
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Tornado spawned by TS Harvey in Crooked Tree Village, Belize.


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From what I can see the center has wobbled a tad south of due west over the last 2 hours, will be interesting to see the latest center fix soon to confirm
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Quoting CybrTeddy:
Good outflow on the N, limited on the south due to dry air that got into the circulation earlier this morning, which is why the recon is not finding higher winds. Whenever you see a big blowup of convection directly over the COC today is when you'll know Irene is strengthening.




nice pic what website is this?
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Quoting aasmith26:


Why was he banned? :(


All I'm gonna say is that WU is not in the habit of permanently banning anyone that is not a real jackwagon.

They won't hit the center on this pass I don't think. They are playing dodge the mountains it looks like.
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why do people want Irene to stay over water?? Can only be one reason.They want it to strengthen and destroy peoples lives! Just sick!
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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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