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: 721 - 671

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

For the next 24 to 48 hours it is pretty much a track heading of 280 degrees.

Once that settles down we will have a much better handle on where Irene is going

Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting Bluestorm5:
Great.... I had 100 comments, but creating new blog restarted it to 1. lol...


LOL same thing happened to me because i wanted to ignore a troll
Member Since: Posts: Comments:
We got lots of discussion in tropics talk
Member Since: Posts: Comments:
All r getting fooled by the expanding convection giving the appearance of a shift further north, gulf coast gotta watch this one!
Member Since: Posts: Comments:
Starting to organize, seems the center has relocated closer to the convection:
Member Since: July 7, 2010 Posts: 0 Comments: 5694
Quoting snow2fire:


How do you report someone?

Is there a way to get message/complaint to Wund?


[ ! ] button to the right of their username.
Member Since: Posts: Comments:
Quoting DFWjc:



Shh, you and Jason need to put the DUNCE cap back on and get back to your lil corners with all the other Lil Jimmies...


See post 704.
(sigh)
Member Since: Posts: Comments:
Quoting Vincent4989:
i'm alone in tropics talk


Im sorry..
Member Since: Posts: Comments:
Quoting snow2fire:


How do you report someone?

Is there a way to get message/complaint to Wund?




Little red exclamation point in the upper right corner of their post. Enjoy :)
Member Since: Posts: Comments:
On August 29/30, new moon and perigee will be less than 40 hours apart. It is not a perfect alignment but spring tides will be higher than normal spring tides.

This is a few days after Irene is forecast to affect the southeast. However high tides will start rising above normal on the 26th and be higher still on Aug 27th and Aug 28th.

I wrote up a blog giving the time of the highest tide of the day and its height for 15 locations in SC, GA, and FL. Check it out if you like.

Even if Irene is held to a Cat 1 or tropical storm due to land interaction, the astronomical influences could result in storm surges higher than people expect.
Member Since: Posts: Comments:
Great.... I had 100 comments, but creating new blog restarted it to 1. lol...
Member Since: Posts: Comments:
Quoting tropicfreak:
Comment 642 reported and ignored.


How do you report someone?

Is there a way to get message/complaint to Wund?


Member Since: Posts: Comments:
Now you are scaring me
Member Since: Posts: Comments:
Quoting Thrawst:


6 hours * have a good one.. poof.


Uh, the SMART thing to do would be to NOT QUOTE something like that!
Member Since: Posts: Comments:
Quoting GTcooliebai:
Makes you wonder when Irene exits the picture, if Jose will form right after, also going back to your post about the forecast for 2005, I also admit that I was fooled into thinking Neutral Years weren't suppose to be that bad, and ironically with the same list of names and all we have a Neutral Year.
I know.Everything is so strange.Weird De-ja-vu.
Member Since: Posts: Comments:
Quoting serialteg:


hiya,

watch out for the DACO this time around :D

LAWLZ
Member Since: July 7, 2010 Posts: 0 Comments: 5694
Thanks. I will bookmark that info.

Quoting Thrawst:


http://www.windfinder.com/forecast/key_largo_mana tee

Forecast gets its data from the GFS model.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
I don't like how things are shaping up for Florida and the East Coast (My area included)...



My mom is not totally believing the models yet... gotta be consistent at least 2 or 3 more times to get the confidence up.
Member Since: Posts: Comments:
698. Relix
Quoting serialteg:


hiya,

watch out for the DACO this time around :D


Hahaha already on that! XD!
Member Since: Posts: Comments:
Quoting fire635:
For the first time in several years... A storm has my attention. I live just north of Tampa on the Florida west coast. With Irene's size and her almost certain track towards the southeast... We are GOING to see effects here. It's just a matter of to what degree. A skirt up.Florida's west coast could potentially devestate us here but even if she slides up the east coast I believe her wind and especially her rain will make things bad across the entire state.... Including Tampa Bay. It's best to start getting prepared. This could very well be the reality check most people have forgotten in Florida.


Very well said! I know it has my attention, and I hope everyone else's!
Member Since: Posts: Comments:
Quoting shadoclown45:
Is a track similar to earl possible once it gets past Hispaniola and cuba?


Unlikely, due to the trough. Once it exits the region, that ridge will build right back in. It's going to be hard to see it doing anything like an OBX direct hit, but you should never leave your guard down.
Member Since: Posts: Comments:
Posts like 677 are ones you just have to laugh at.And I'm laughing at them.
Member Since: Posts: Comments:
Quoting presslord:


Should we understand this to mean you don't put much stock in a potential east Coast scenario?


For right now the main concern for the U.S. is Florida and Louisiana, thereafter there could be impacts the southeast or southeastern seaboard.
Member Since: Posts: Comments:
Quoting serialteg:
Good evening fellow Wundergrounders,

All my fellow Puerto Ricans a Hola to all!

Looks like an F5 (browser refresh) event is in order. Everything from the Islands to Florida, especially with the model consensus, is rattled.

Seems like this is the storm Emily missed... and what about that centre fix being a little higher?



I'm with Keeper on this one, we may get a higher centre fix at the 11

Are you preparing? I live inland, in a non-flood zone. But a lot of my family members (Aunts, Uncles, Grandparents, Cousins) live near flood zones.
Member Since: July 7, 2010 Posts: 0 Comments: 5694
Quoting washingtonian115:
I think it's kinda ironic that Harvey exsist the picture and Irene comes in.Lol.
Makes you wonder when Irene exits the picture, if Jose will form right after, also going back to your post about the forecast for 2005, I also admit that I was fooled into thinking Neutral Years weren't suppose to be that bad, and ironically with the same list of names and all we have a Neutral Year.
Member Since: Posts: Comments:
690. DFWjc
Quoting DFWjc:


could you repeat the question?


Quoting Drakoen:
It seems like a very tough call to say whether or not Irene will stay south of Cuba or possible graze or portions of Hispaniola and Cuba. There are reliable computer forecast models in both camps. The GFDL, UKMET,and the CMC in the southern camp and the GFS, ECMWF, and HWRF in the northern camp. The former camp certainly allows for more intensification of Irene and greater potential as atmospheric conditions and oceanic conditions are supportive of a Major Hurricane. The latter camp is a lot much more complicated; subtle movements of Irene, how much land it crosses over and for how long, will determine how much strengthening can occur before it impacts Florida. If we assume that Irene avoids land minimal as show on the ECMWF (the model I consider to be the most reliable)then the potential for a significant storm is greater than the GFS and HWRF who are in that same camp. Ultimately, it will really come down to how potent the trough is. The Skill Score of the 500mb heights shows the ECMWF and UKMET leading, adding to the difficulty in the forecast since these models are in opposite camps. All in all, everyone in Florida should be on their guard for this storm as there is a high potential for impact from this storm in one way or another. Taking into account the southern solution models, there should be around a medium potential for Louisiana.
Member Since: Posts: Comments:
Quoting DontAnnoyMe:


Don't take it personally, a LOT of posts don't get replies on here.


Thanks and also i had 80 posts im down to 30 LOL! glitch much
Member Since: Posts: Comments:
Well, there is a NASCAR race at Bristol, TN next weekend... wondering if Irene will affect that weekend? Irene is supposed to go over GA/SC/NC/TN on Friday/Saturday?
Member Since: Posts: Comments:
Quoting Relix:
*ahem*

Yeah I meant that Irene's center could be further to the north than expected. :P!


hiya,

watch out for the DACO this time around :D
Member Since: Posts: Comments:
685. ackee
I cant wait to see the NHC cone of DOOM if it will remain the same or shift to the left or right guess we see
Member Since: Posts: Comments:
Quoting presslord:


Should we understand this to mean you don't put much stock in a potential east Coast scenario?


IMO...I'd be careful to discount the east coast right now...as this could reform more toward the northern convective burst....shifting model tracks slightly to the right....
Member Since: Posts: Comments:
i'm alone in tropics talk
Member Since: Posts: Comments:
Quoting InTheFloridaKeys:
Yeah, this doesn't help my uneasy feelings I already have here.... I am in Key Largo thanks!



http://www.windfinder.com/forecast/key_largo_mana tee

Forecast gets its data from the GFS model.
Member Since: Posts: Comments:
Is a track similar to earl possible once it gets past Hispaniola and cuba?
Quoting DFWjc:


could you repeat the question?
Member Since: Posts: Comments:
Quoting shadoclown45:
Why am i being ignored?
2 posts and no response?


Don't take it personally, a LOT of posts don't get replies on here.
Member Since: Posts: Comments:
Quoting shadoclown45:
Why am i being ignored?
2 posts and no response?


have u noticed how fast the blog moves? try not to let it get to you ;)
Member Since: Posts: Comments:
Quoting HurricaneDean07:
Tropical Cyclone activity to date:(August 21st)
1933: 8 Named Storms
1969: 4 Named Storms
1995: 8 Named Storms
1998: 3 Named Storms
2004: 5 Named Storms
2005: 9 Named Storms
2007: 5 Named Storms
2008: 6 Named Storms
2010: 4 Named Storms
2011: 9 Named Storms

So as of August 21st, we are tied with 2005 For FIRST PLACE with 9 named storms, 1998 is last with 3 Named Storms...

Pretty impressive first half of the season, lets see if we can keep it up in the last half...


I just hope we don't end up with the greek alphabet...those were weird times...
Member Since: Posts: Comments:
Quoting Drakoen:
It seems like a very tough call to say whether or not Irene will stay south of Cuba or possible graze or portions of Hispaniola and Cuba. There are reliable computer forecast models in both camps. The GFDL, UKMET,and the CMC in the southern camp and the GFS, ECMWF, and HWRF in the northern camp. The former camp certainly allows for more intensification of Irene and greater potential as atmospheric conditions and oceanic conditions are supportive of a Major Hurricane. The latter camp is a lot much more complicated; subtle movements of Irene, how much land it crosses over and for how long, will determine how much strengthening can occur before it impacts Florida. If we assume that Irene avoids land minimal as show on the ECMWF (the model I consider to be the most reliable)then the potential for a significant storm is greater than the GFS and HWRF who are in that same camp. Ultimately, it will really come down to how potent the trough is. The Skill Score of the 500mb heights shows the ECMWF and UKMET leading, adding to the difficulty in the forecast since these models are in opposite camps. All in all, everyone in Florida should be on their guard for this storm as there is a high potential for impact from this storm in one way or another. Taking into account the southern solution models, there should be around a medium potential for Louisiana.


Should we understand this to mean you don't put much stock in a potential east Coast scenario?
Member Since: Posts: Comments:
672. DFWjc
Quoting shadoclown45:
Why am i being ignored?
2 posts and no response?


could you repeat the question?
Member Since: Posts: Comments:
Good evening fellow Wundergrounders,

All my fellow Puerto Ricans a Hola to all!

Looks like an F5 (browser refresh) event is in order. Everything from the Islands to Florida, especially with the model consensus, is rattled.

Seems like this is the storm Emily missed... and what about that centre fix being a little higher?



I'm with Keeper on this one, we may get a higher centre fix at the 11
Member Since: Posts: Comments:

Viewing: 721 - 671

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
57 °F
Overcast