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: 2921 - 2871

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 WeatherNerdPR:

F-F-Fine! H-H-How are y-you???



F-F-fine. lol You're not cold, are you?
Member Since: Posts: Comments:
When is the next HH flight going in?
Member Since: Posts: Comments:
Quoting clwstmchasr:


I don't disagree at all. But the US has been sparred now for 3 years (5 years with a major) that sometimes it is hard to buck the trend. I do think it will make landfall - where? Somewhere between Mobile and the OBX.


"Trends" are irrelevant here; only current atmospheric conditions determine the outcome. But yes, anywhere from the Panhandle to the OBX is still in the picture on this one imho.
Member Since: August 17, 2005 Posts: 26 Comments: 16874
2918. unf97
Quoting 34chip:
Two words guys Flip Flop Flip Flop. Till its on the door steps of someone Flip Flop!!!! So stop with Florida is in the clear. The Southeast is not out of it at all!!!



Amen! Everyone needs to be really vigilant regarding this situation. No one is in the clear!
Member Since: Posts: Comments:
One thing worth pointing out, should Irene miss Florida to the east, it will probably be the Carolinas that get whacked, and over those waters it could be very strong. US in general is not being saved by these eastward trends. Full recurve before the Outer Banks is not likely.
Member Since: Posts: Comments:
Quoting stormwatcherCI:
Doing good. Got my eye on Irene. How are you ?


Good, thanks! Watching Irene as well and hoping it keeps shifting eastward. Looks like our luck has run out this year, huh? No more big trofs lifting out and sending the storms out to sea.
Member Since: Posts: Comments:
Quoting KennyNebraska:
Irene has taken a WSW jog. Check it out.

http://www.ssd.noaa.gov/goes/flt/t2/flash-vis.htm l
Which is expected when you look at the steering layer. I said this earlier this morning and when you look at the loop you posted you can definitely see it.
Member Since: Posts: Comments:
Quoting Gearsts:
Me puedes dar el link de ese loop?

Aqui esta, solo unde el lugar que quieres ver de cerca.
I still prefer English :P
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting 34chip:
Two words guys Flip Flop Flip Flop. Till its on the door steps of someone Flip Flop!!!! So stop with Florida is in the clear. The Southeast is not out of it at all!!!


Chips is it true that models tend to move east at night then back west during the daylight?
Member Since: Posts: Comments:
2912. WxLogic
Quoting InTheCone:
A definite shift east from the 0z runs..



If you notice they're clustering around the NHC track... so I would expect NHC to to keep it the way it is now with potentially an ever so slight shift to the E closer to the coast instead of fully inland.
Member Since: Posts: Comments:
No offense meant; but the US sure needs Haiti, DR, & PR to run some interference with those mountains...If she manages to miss the mountainous islands she could be a real monster.

Member Since: August 17, 2005 Posts: 26 Comments: 16874
Quoting stormwatcherCI:
I remember. I am in Grand Cayman and he passed 30 miles south of us. We had winds reported at 157 mph. That was the first hurricane my kids experienced.


I was actually in St Thomas USVI at a fishing tournament to scatter my father's ashes where he caught his world record marlin and it was pretty intense there but nothing like what happened here a few days later :(
We lost infrastructure for months, it was a total nightmare!!!
I have a really bad feeling about this one so am heading to Pricesmart as soon as they open to stock up on EVERYTHING we use regularly...
One Love
Member Since: Posts: Comments:
2909. Gearsts
Quoting WeatherNerdPR:

F-F-Fine! H-H-How are y-you???
Me puedes dar el link de ese loop?
Member Since: Posts: Comments:
2908. WxLogic
Quoting whepton3:



Wonder what's driving the E shift in the HWRF..

More intensification and quicker forward motion to catch the weakness more east?


From what I can tell is the placement and speed of Irene. The weakness for now (based on 00Z/06Z) is now being modeled to be a bit further E not much in the big scope of things and the Bermuda High not pushing Irene further W as before based on some of the model suite as some of them still don't buy it... yet.

One thing to note is that HWRF brings Irene further E when crossing DR which would imply the track that is taking which is a bit further away from the E FL coast, but if Irene doesn't do this which is not expected to at this time then I would expect HWRF to shift back to the W some... closer to GFS.
Member Since: Posts: Comments:
HH plane has 35knot flight level winds already, and it's nowhere near the centre yet. It's a large storm, and I dare say it's at least 60mph.
Member Since: Posts: Comments:
2905. Gearsts
Flt. Lvl. Wind (30s): From 62° at 38 knots (From the ENE at ~ 43.7 mph)
Air Temp: 16.0°C* (~ 60.8°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 40 knots (~ 46.0 mph
Member Since: Posts: Comments:
800 AM UPDATE POLL

A. 40 MPH-50 MPH
B. 50 MPH 60 MPH
C. 60 MPH 70 MPH
D. HURRICANE IRENE- CAT 1
E.OTHER
Member Since: Posts: Comments:
Quoting KennyNebraska:


TS Irene DOOMcon Level at GUARDED




Hahahah! I love it! The jokers on our local paper's comment section think every storm warning is manufactured by the insurance industry so they can they raise the rates. They'd like this one.
Member Since: Posts: Comments:
Quoting weatherwart:
Morning all! Hey stormwatcher, how you are you doing?

F-F-Fine! H-H-How are y-you???
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting Autistic2:


Perfect. We now have an offical DOOMCON chart!


Note the image location so that it can be posted by others as needed. I may not be around all the time.
Member Since: Posts: Comments:
2899. 34chip
Two words guys Flip Flop Flip Flop. Till its on the door steps of someone Flip Flop!!!! So stop with Florida is in the clear. The Southeast is not out of it at all!!!
Member Since: Posts: Comments:
Irene has taken a WSW jog. Check it out.

http://www.ssd.noaa.gov/goes/flt/t2/flash-vis.htm l
Member Since: Posts: Comments:
I think the spaghetti models and the lines with center fix positions can mislead people... especially when you compare a plot point on a map to the size of the system.

Sometimes people see that line just offshore and think "whew, it'll miss us!".

While it may have huge implications in terms of the area around a direct landfall, the overall effect on the area can be much the same.
Member Since: Posts: Comments:
2896. vince1
Quoting popartpete:
Sorry Chiklit, I was just joking. I know this is serious stuff. I'm a learned tropical weather person, and the forecaster, if you will, for my local emergency management. That was really about Facebook anyway. I just thought others would get a kick out of it.

I got it...but I'm proud to say I haven't succumbed to all those time-killing, life-sucking Facebook sensations (Farmville, ugh).
Member Since: Posts: Comments:
2894. hotrods
Good Morning, Could this turn out to be David track?
Member Since: Posts: Comments:
Quoting A4Guy:



yes...I should have said "keeps the center off the coast."

Overall, I wouldn't be surprised to continue to see an eastward bias....the TVCN consensus i being pulled west by some of the outliers...but then again, there are one or two far eastern outliers also.

Needless to say, I live in coastal Broward, and will be watching closely. I fly out tmrw for a business trip, and back Thurs. will probably change my flight to come back Weds night, depending on how things look Tuesday a.m.


Indeed. Though, when you have two models showing a similar, much further west path, they can't definitely be called outliers. They are considered outliers at this time, but they are showing that path for a reason, so there is still a possibility. Eastern Gulf is less likely, but still a possibility. There have certainly been much more significant track changes than this would need to make it there.
Member Since: Posts: Comments:
Quoting KennyNebraska:


TS Irene DOOMcon Level at GUARDED




Perfect. We now have an offical DOOMCON chart!
Member Since: Posts: Comments:
Quoting weatherwart:
Morning all! Hey stormwatcher, how you are you doing?
Doing good. Got my eye on Irene. How are you ?
Member Since: Posts: Comments:
Morning all! Hey stormwatcher, how you are you doing?
Member Since: Posts: Comments:
A definite shift east from the 0z runs..

Member Since: Posts: Comments:
Expect the next TWO in 30 minutes.
Member Since: Posts: Comments:
Quoting WeatherNerdPR:

A big one.


That run there

Ain't.
No.
joke.
Member Since: Posts: Comments:
2885. A4Guy
Quoting NICycloneChaser:


The HWRF really isn't far from the coast, and shows a strong enough system that it would probably be producing hurricane conditions on the east coast of Florida.



yes...I should have said "keeps the center off the coast."

Overall, I wouldn't be surprised to continue to see an eastward bias....the TVCN consensus i being pulled west by some of the outliers...but then again, there are one or two far eastern outliers also.

Needless to say, I live in coastal Broward, and will be watching closely. I fly out tmrw for a business trip, and back Thurs. will probably change my flight to come back Weds night, depending on how things look Tuesday a.m.
Member Since: Posts: Comments:
Quoting StormJunkie:


A significant jump/reform to the N is one of the reasons.

Will be interesting to see what da plane finds.


We've been watching that jump N on the center...

Wondering if a more northern and eastern pass over Hispaniola might be in the cards?

Member Since: Posts: Comments:
Quoting NICycloneChaser:


GFS has a landfall.

A big one.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting Neapolitan:

It's far too early to assume anything like that, of course. Keep your fingers crossed, sure, but nobody in Florida should be signalling the all-clear for at least a few more days.


I agree, until Irene dissipates no one is "in the clear" yet IMO
Member Since: Posts: Comments:
Quoting clwstmchasr:


Model guidance is definitely shifting east. Wouldn't it be amazing if the US gets sparred from another hurricane?


I doubt there is much chance it misses the US, although not entirely impossible. The OBX just stick out so far that I can't imagine it would shift far enough E to put them out of the picture.
Member Since: August 17, 2005 Posts: 26 Comments: 16874
Quoting negriltracy:



Yup :(
Gilbert came into the Caribbean at about the same spot, did not make the turn and careened west then right across Jamrock...eeks!!!
I remember. I am in Grand Cayman and he passed 30 miles south of us. We had winds reported at 157 mph. That was the first hurricane my kids experienced.
Member Since: Posts: Comments:
Quoting barotropic:
cat 4 hurr showin up in bahamas missing florida. This combines with GFS and the north and east trends suggests really good news for florida


IMO Those in Florida (including me) are no out of the woods yet. The NHC has had to shift a few tracks this year throughout a storms life, but the NHC has done a pretty good job at finding where it will eventually end up right from the get go. Again, it can all still change, even drastically, but the fact that Florida is even in the cone warrants some staying up to date and preparing for anything. JMO.

Member Since: Posts: Comments:
Doomcon 1 here in saint augustine=forget about Irine until tonight and go to church and enjoy my day.
Member Since: Posts: Comments:
I am sticking with GFS personally

Quoting NICycloneChaser:


GFS has a landfall.
Member Since: Posts: Comments:
Quoting coffeecrusader:
Looks like us folks on the west coast of Florida are in the clear... WHOOOOO! Sorry east coast.

It's far too early to assume anything like that, of course. Keep your fingers crossed, sure, but nobody in Florida should be signalling the all-clear for at least a few more days.
Member Since: Posts: Comments:
Quoting NICycloneChaser:


The HWRF really isn't far from the coast, and shows a strong enough system that it would probably be producing hurricane conditions on the east coast of Florida.


Correct. A track like the GFS/HWRF is showing (with such an intensity) would still be horrific for the E coast of FL.
Member Since: Posts: Comments:
Quoting whepton3:



Wonder what's driving the E shift in the HWRF..

More intensification and quicker forward motion to catch the weakness more east?
Well, more intensification due to the greater time over water
Member Since: Posts: Comments:
Quoting whepton3:



Wonder what's driving the E shift in the HRWF..

More intensification and quicker forward motion to catch the weakness more east?


A significant jump/reform to the N is one of the reasons.

Will be interesting to see what da plane finds.
Member Since: August 17, 2005 Posts: 26 Comments: 16874

Viewing: 2921 - 2871

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.

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron