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: 3571 - 3521

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

If you take the 30 image loop from NASA/MSFC Interactive GOES Data Selector, Irene has NOT moved west overnight.

It has moved mainly NW.
Member Since: Posts: Comments:
Quoting hurricanehunter27:
Lets get this straight, she is stacked on ALL levels, she does have a defined closed center, and she needs to rap convection around south side before it becomes a hurricane. Correct?



that spin your are seeing is mid level the low level center is due south of that spin but i wail sya that in the last 2 frames (13:15,13:45) she does appear to be getting tighter and convection is try TRYING to wrap around
Member Since: July 21, 2010 Posts: 0 Comments: 1181
If Irene moves straight over the interior of Hispanola like all model guidance is calling for, well, the possibility exists that Irene will degenerate into a remnant low, not saying it will, but it sure can happen.
Member Since: Posts: Comments:
Quoting barotropic:


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.
must be heading WSW again?
Member Since: Posts: Comments:
Quoting SavannahStorm:
GFS 6-Day Total:

"It's Gon Rain!"

well, I'm in the heaviest rain region in NC.
Member Since: Posts: Comments:
Quoting weatherguy03:
TS Irene Morning Update Aug. 21st, 2011


Outstanding! Thank you!
Member Since: Posts: Comments:
Good morning everyone.

I see we had fairly significant changed with Tropical Storm Irene last night. First, it ingested dry air, which was limited intensification for at least the rest of the morning. Secondly, the center formed farther north than expected, which is the significant jump northward the NHC noted was possible last night.

Member Since: Posts: Comments:
Quoting hurricanehunter27:
? Seems pretty defined to me IMO.
Recon hasn't been able to find one due west wind reading in the circulation. Pretty ill-defined for a 50mph cyclone.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Lets get this straight, she is stacked on ALL levels, she does have a defined closed center, and she needs to rap convection around south side before it becomes a hurricane. Correct?
Member Since: Posts: Comments:
3561. ncstorm
Quoting WeatherNerdPR:
Seems like it's gonna clip SW PR...


which would put PR in the worst part of the storm
Member Since: Posts: Comments:
3560. cwf1069
Now that she is vertically stacked, is when the show of intensification begin. She should get hurricane status before making landfall between sw of Puerto Rico and ne of Dominican Republic trough the Mona Passage. Not to much interaction with land,so strengthening wont be a problem but more tend to feel the weakness, and may be turning before south Florida. Hope that materialized. Now leaving to work, be back tonight to see what Irene been doing to boricuas. God bless all of them.
Member Since: Posts: Comments:
Quoting zparkie:
Last year there was a gentleman called StormW on here, I would read his blogs and he seemed pretty accurate and knowledgable about weather. This year I dont see him blogging. Any one know if he retired from this or what might have happened? If so let me know, everyone would request info from him, I think he got married and there was even a big rumor that proved to be false that he died. but I wonder where he is now? anyone know?

I think this is what your looking for.
Link
Member Since: Posts: Comments:
Quoting wxhatt:


That track could be worse...


And if that does happen, she'll probably be a decent hurricane.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
Seems like it's gonna clip SW PR...
Member Since: Posts: Comments:
Quoting Vincent4989:

I'm guessing it as a minimal F2 tornado
I would agree with F2 as well. I don't think this is EF-3, even though it looks like one. Tornadoes in hurricane is MUCH weaker than tornadoes in supercells... btw, what a tornado season 2011 had been :\
Member Since: Posts: Comments:
Quoting ncstorm:
Has anyone noticed that the bermuda is becoming in the bullseye in the ensemble members for 98L..trending west



Yep. TampaSpin noticed. There may be some pumping of the ridge later.
Member Since: July 7, 2010 Posts: 0 Comments: 474
Quoting MiamiHurricanes09:
Still looooooooonnnnnnngggggggggg ways out before it becomes a hurricane. Circulation remains pretty ill-defined.


This weak structure is going to perhaps add credo to staying lower in latitude IMO.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Still looooooooonnnnnnngggggggggg ways out before it becomes a hurricane. Circulation remains pretty ill-defined.


? Seems pretty defined to me IMO.
Member Since: Posts: Comments:



seems to be getting alittle tighter in the 13:45 fram howvever the center needs to get under the mid level one if she wants to make a run at hurricane
Member Since: July 21, 2010 Posts: 0 Comments: 1181
Quoting GetReal:




High pressure to the north of Irene....


hard to forcast those highs so it is something to keep your eyes on
Member Since: Posts: Comments:
Here in the NW of Puerto Rico Supermarkets and Gas stations are full, is like they just woke up after been hanging out all night and they realized that time is running out.
Member Since: Posts: Comments:
Quoting SavannahStorm:
GFS 6-Day Total:

"It's Gon Rain!"



No big deal, we've had about what's in the bulls eye at my place in Florida over the last several days :)
Member Since: Posts: Comments:
3545. wxhatt
Quoting FSUCOOPman:
@3282

Anyone know what the UK model is picking up on that's sending it so much further west than the other models?


It is a dynamical model that covers just a portion of the globe. These are less useful, unless the hurricane happens to start out inside the domain the model covers and stay there. Hurricanes moving from outside the model domain into the model domain are not well handled. An example of this kind of model is the NAM model covering North America and the surrounding waters.
Member Since: Posts: Comments:
Quoting AussieStorm:

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

It's very rare to get tornadoes in Belize. They might not even use the F/EF scale, but if they do use it, I haven't seen a rating given.
Member Since: Posts: Comments:
Quoting chrisdscane:
she wont strenthen much until she stacked it may be a while


She looks pretty stacked on the vorticity maps.. Post #3525
Member Since: June 21, 2010 Posts: 0 Comments: 528
Still looooooooonnnnnnngggggggggg ways out before it becomes a hurricane. Circulation remains pretty ill-defined.


Member Since: September 2, 2009 Posts: 130 Comments: 21194
she wont strenthen much until she stacked it may be a while
Member Since: July 21, 2010 Posts: 0 Comments: 1181
Quoting Bretts9112:

Link

Thanks, but this one showed all the models too. Though this is good too.
Member Since: Posts: Comments:
3539. GoWVU
Nice morning here in the South Carolina low country, just going to sit back and watch and listen to how Ms. Irene plays out.
Member Since: Posts: Comments:
Quoting weatherguy03:
TS Irene Morning Update Aug. 21st, 2011


Wow! Hey Bob!
Member Since: Posts: Comments:
GFS 6-Day Total:

"It's Gon Rain!"

Member Since: Posts: Comments:
When is the next major run by any of the models?
Member Since: Posts: Comments:
Quoting Bluestorm5:
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.

I'm guessing it as a minimal F2 tornado
Member Since: Posts: Comments:
Quoting stormpetrol:
Time: 14:02:00Z
Coordinates: 16.8333N 62.9W
Acft. Static Air Press: 843.2 mb (~ 24.90 inHg)
Acft. Geopotential Hgt: 1,537 meters (~ 5,043 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 7° at 3 knots (From the N at ~ 3.4 mph)
Air Temp: 16.5°C* (~ 61.7°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 4 knots (~ 4.6 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots (~ 23.0 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
(*) Denotes suspect data

Think this might be new center fix , not sure yet!
16.8 roger
Member Since: Posts: Comments:
3533. scott39
Quoting StormJunkie:


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.
not very well I would assume! If it degenerates over mountains would the forward speed to the W be the same and would the trough still catch it?
Member Since: June 13, 2009 Posts: 0 Comments: 6912
3532. GetReal
Quoting FSUCOOPman:
@3282

Anyone know what the UK model is picking up on that's sending it so much further west than the other models?




High pressure to the north of Irene....
Member Since: Posts: Comments:
3531. WxLogic
36HR:



Pretty deep TROF.
Member Since: Posts: Comments:
Quoting WxLogic:
12 NAM @24HR:



So, the high moves inland and the trof moves down meaning to us groundlings what exactly?

The longrange PR radar lines up with my highly scientific method of holding a clear plastic straw over various IR satellite images and trying to 1) find the current COC and 2) tilt it until I think I can see where its been and it looks to have a bead on South PR. After that I had to rely on you smart folks to explain the various forecast maps and how it will play out with that
Member Since: Posts: Comments:
TS Irene Morning Update Aug. 21st, 2011
Member Since: Posts: Comments:
Quoting chrisdscane:




so she not even verticly stacked yet
looks like another tilted storm so far. definitely not in RI mode.

Cruising fast to the west.
Member Since: Posts: Comments:
Quoting chrisdscane:
has levi posted his vid?
No. He traveled somewhere last night.
Member Since: Posts: Comments:
Quoting chrisdscane:




so she not even verticly stacked yet


apparently not.
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting chrisdscane:




so she not even verticly stacked yet

Seems pretty stacked to me.
850MB

700MB

500MB
Member Since: Posts: Comments:
3524. ncstorm
From Allan Huffman

Because, in about 3-5 days the upper level pattern over Emily will become very favorable for intensification and it will be moving over very warm waters near Cuba and potentially in the Florida Straits. If Irene does not move across Hispaniola, we could have a major hurricane crossing the eastern portions of Cuba heading towards the south Florida coastline. I think the storm will skirt very near the south shore of Hispaniola and thus some weakening will occur, but I do not think the storm will fall apart.

Beyond this the global models have come into better agreement overnight showing a more easterly track with a turn NW through eastern Cuba and a close pass to southeast Florida before moving N or NNW near the northern Florida/Georgia/southern South Carolina coast. The 6z GFS has shifted a bit east and is close to the ECMWF and GGEM. This means a definite risk for anywhere from Miami to Cape Hatteras. I have not ruled out a western Florida hit either or an eastern Gulf threat, there is still a great deal of uncertainty. There is also a big risk for very heavy rains in the southeast and possibly the mid-Atlantic from this as well after landfall so that will have to be watched.

I hope to post again this afternoon after the 12z guidance and dissect each model a bit more.

Member Since: Posts: Comments:
Time: 14:02:00Z
Coordinates: 16.8333N 62.9W
Acft. Static Air Press: 843.2 mb (~ 24.90 inHg)
Acft. Geopotential Hgt: 1,537 meters (~ 5,043 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 7° at 3 knots (From the N at ~ 3.4 mph)
Air Temp: 16.5°C* (~ 61.7°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 4 knots (~ 4.6 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots (~ 23.0 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
(*) Denotes suspect data

Think this might be new center fix , not sure yet!
Member Since: Posts: Comments:
Quoting Gorty:


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?


just gonna have to give her some time
Member Since: Posts: Comments:
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.
Member Since: Posts: Comments:

Viewing: 3571 - 3521

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