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: 571 - 521

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

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.
Member Since: Posts: Comments:
Quoting washingtonian115:
I'm 41 also!!!.1970 to eh?.And @424 so not cool man.


1970 right, good music...!
Member Since: Posts: Comments:
I find it hilarious and disturbing that no matter if it comes from the west or east of Florida; I still managed to get hit.
Member Since: Posts: Comments:
What I don't comprehend is how someone can create a name with JFV or Jason, with today's date, with all the experience we had with such id's...

Also, although we cannot generalize, if I see someone posting
^___^, for me that means a troll blogger....

Is there a way to create stronger blog controls?
Member Since: Posts: Comments:
Quoting Bluestorm5:
whew, I think JFV is gone. Seriously, why my ignored button not working?

Anyway, when the next recon plane heading out?


Have you made a blog post? I don't think you can ignore anyone until your blog is activated.
Member Since: Posts: Comments:
Quoting LADobeLady:


It takes a few minutes to kick in. This blog is moving fast, give it time to catch up.


lol. But that's just not true.
Member Since: Posts: Comments:
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.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:


Yo, don't be hittin' on my show!

LOL

LOL
Member Since: July 7, 2010 Posts: 0 Comments: 5690
Quoting GetReal:



If it goes into the mountains.....


Your absolutely right, I was basing my opinion on the official forecast.
Member Since: August 19, 2005 Posts: 5 Comments: 5450
Quoting Bluestorm5:
Why is my ignored list button NOT WORKING?


You have to make a blog entry first, for it to work.
Member Since: Posts: Comments:
Quoting GTcooliebai:
notice, not a northeast turn, in fact after turning north a bend back towards the west. Interesting.


levi32 had a great explanation of this earlier today it looks like that is what going to happen
Member Since: Posts: Comments:
Where's baha?
Member Since: Posts: Comments:
ok either west coast of florida or east coast of florida seems to me north carolina and virginia are in deep trouble so best be prepared in any event
Member Since: Posts: Comments:
555. Skyepony (Mod)
Fresh WINDSAT of 98L
Member Since: Posts: Comments:
Quoting WeatherNerdPR:

It's gonna be OVER 9,000!!!! by morning. LOL


Yo, don't be hittin' on my show!

LOL
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting MississippiWx:



Here's what is terrifying about these model runs: THEY ARE ALL THREATENING THE US, CUBA, HISPANIOLA, PR, AND THE LESSER ANTILLES. No matter where it ends up, it'll still threaten land.
Member Since: July 7, 2010 Posts: 0 Comments: 5690
whew, I think JFV is gone. Seriously, why my ignored button not working?

Anyway, when the next recon plane heading out?
Member Since: Posts: Comments:
Quoting stormwatcherCI:
I agree. That is the kind of thing he thinks is funny trying to impersonate another blogger.

I did like the picture of him and his dad with his mom wearing the red underwear!
Member Since: Posts: Comments:
If this goes, it will really help with the track forecast...


B. POSSIBLE G-IV SURVEILANCE MISSION FOR THE
SAME SYSTEM AT 22/0000Z.


Hope it goes.
Member Since: Posts: Comments:
Gotta run now. Back in the morning.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
It will be interesting to see how the new bridge over JewFish Creek affects northbound during the evacuation
Member Since: Posts: Comments:
Quoting Bluestorm5:
Why is my ignored list button NOT WORKING?


It takes a few minutes to kick in. This blog is moving fast, give it time to catch up.
Member Since: Posts: Comments:
Quoting ProgressivePulse:
I really do have to say this is going to be an extremely tough situation with regards to planning. What survives over the mountains, if anything, has the potential to rapidly intensify as is being depicted in the models and in the NHC discussion. Tough picking up a family and getting out of dodge 24hrs ahead of landfall. Money is tight with most everyone right now to further complicate the matter.
I hope that if the storm comes you still manage to get out of harms way. and keep your family safe.
Member Since: Posts: Comments:
Quoting InTheFloridaKeys:
Going to be an interesting next few days... I am in Key Largo in the Florida Keys.....


Nassau, Bahamas here.. although I believe you are more at risk than me, get prepared ahead of time!
Member Since: Posts: Comments:
Quoting Tazmanian:




this is going too be fun


No way!!! My parents are vacationing in Miami for a month
Member Since: Posts: Comments:
Quoting weatherguy03:
We wont have one of those strong troughs to really kick this system out. So it will be more of a gradual turn to the North. So if it does move East of Florida it could ride right up the East Coast.


in the gulf stream..
Member Since: Posts: Comments:
Quoting sunlinepr:


I thing he's JFV, with a Jason name...
I agree. That is the kind of thing he thinks is funny trying to impersonate another blogger.
Member Since: Posts: Comments:
looks like Irene has taken care of the dry air issue to is sw that was present there earlier. That dry air slot is almost gone now.So the genreal track guidance has pushed a bit west overall?
Member Since: Posts: Comments:
Why is my ignored list button NOT WORKING?
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
I just had to read over 1200 posts just to catch up...

SLOW THE HECK DOWN!

lol.

It's gonna be OVER 9,000!!!! by morning. LOL
Member Since: July 7, 2010 Posts: 0 Comments: 5690
Quoting DontAnnoyMe:


See ya!
There you are!.Were wondering when you gonna come out of your hibernation.
Member Since: Posts: Comments:
Quoting weatherguy03:
We wont have one of those strong troughs to really kick this system out. So it will be more of a gradual turn to the North. So if it does move East of Florida it could ride right up the East Coast.


Exactly. A nearly straight north path for a good ways is likely.
Member Since: Posts: Comments:
Quoting ProgressivePulse:
I really do have to say this is going to be an extremely tough situation with regards to planning. What survives over the mountains, if anything, has the potential to rapidly intensify as is being depicted in the models and in the NHC discussion. Tough picking up a family and getting out of dodge 24hrs ahead of landfall. Money is tight with most everyone right now to further complicate the matter.
Excellent point.
Member Since: Posts: Comments:
Quoting ProgressivePulse:
I really do have to say this is going to be an extremely tough situation with regards to planning. What survives over the mountains, if anything, has the potential to rapidly intensify as is being depicted in the models and in the NHC discussion. Tough picking up a family and getting out of dodge 24hrs ahead of landfall. Money is tight with most everyone right now to further complicate the matter.



If it goes into the mountains.....
Member Since: Posts: Comments:
Quoting NavarreMark:


Honestly don't think it can ramp up to that level by the time it gets to S FL, but if it slips a little to the west and gets into the NE GOM it may. Then its gonna be KABLAMMO!!!

Just sayin.


That's what i'm saying, it could do a Wilma/Charley-like and hit Florida, but who knows.
Member Since: Posts: Comments:
Quoting presslord:


maybe she'll just buzzsaw the coast offshore...we just spent $28 million 'renourishing' Folly Beach...wouldn't take much to suck all that sand back into the sea...


Same here. Always doing beach renourishment.
Member Since: Posts: Comments:
Going to be an interesting next few days... I am in Key Largo in the Florida Keys.....
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
I just had to read over 1200 posts just to catch up...

SLOW THE HECK DOWN!

lol.


Like I said, this blog will be going INSANE during the next week. it's been just under 1.5 hours and up to 500 posts.
Member Since: Posts: Comments:
Quoting stormwatcherCI:
Ivan came in further south and may be in the past for some but for those of us in Grand Cayman he will always be in the here and now. Bad memories with Ivan.


Pensacola as well.
Member Since: Posts: Comments:
Quoting stormhank:
Im near the tallahasse area..anyone think we would get much rain from this?? I saw the euro n gfs runs that after affecting florida they turn irene nw into georgia instead of out to sea??


So am I and it's just a wait and see....I am leaving town on Monday and a little worried but a relative is house sitting. I would not think that we have to worry too much unless the "angle" of land fall and the inland movement leaves us in the training pattern......Don't see that happening unless she comes in around the Panhandle and then moves NE into GA.
Member Since: Posts: Comments:

Viewing: 571 - 521

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
66 °F
Overcast