Potentially dangerous 92L steadily developing; Igor nears hurricane strength

By: Dr. Jeff Masters , 3:04 PM GMT on September 11, 2010

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A tropical disturbance (92L) over the Eastern Caribbean, a few hundred miles south of Puerto Rico, is steadily organizing and appears likely to develop into a tropical depression by tonight or Sunday morning. Satellite loops show an impressive and expanding region of heavy thunderstorms, with good spiral banding and respectable upper-level outflow on all sides. Long range radar out of Puerto Rico shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. However, the rain bands are becoming more intense and more organized. San Juan, Puerto Rico reported a heavy rain squall at 8:44 am this morning, and radar estimates suggest two inches of rain fell in this squall just southeast of San Juan. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are at near-record warmth, 30°C, and these warm waters extend to great depth. Water vapor satellite loops show a large area of dry air lies to the north and west of 92L, and this dry air could interfere with development at times over the next few days.


Figure 1. Morning satellite image of 92L.

Track forecast for 92L
The disturbance is moving west-northwest at 11 mph, and steering currents favor a continuation of this motion for the next three days. Model support for development is scattered. The GFS and NOGAPS models do not develop 92L. The GFDL and ECMWF models predict development, with a track taking 92L into Mexico's Yucatan Peninsula on Wednesday. The HWRF model has a more northwesterly track, taking 92L over the Dominican Republic, Haiti, and Cuba, but this model has been trending too far north in its tracks. I expect 92L will follow a path south of the islands, bringing it near or just south of Jamaica on Monday, then into the Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches tonight through Monday morning; southern Haiti can expect similar rains Sunday through Monday, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba will probably escape 92L's heaviest rains in this scenario (Figure 2.)

Intensity forecast for 92L
I can't find any reason to doubt this will be a tropical storm by Sunday or Monday, and potentially a Category 1 or 2 hurricane by Wednesday, if 92L avoids passage over Hispaniola and Cuba. The SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and makes 92L a Category 1 hurricane by Monday night. Water temperatures are certainly warm enough to support development. The main detriment to intensification is likely to be dry air, and 92L could wrap in some of the dry air to its northwest at times, slowing down development. The first Air Force Hurricane Hunter mission into 92L is scheduled for Sunday afternoon, but there will be a research mission by the National Center for Atmospheric Research G-V jet today that will give us valuable information on 92L's large scale environment and potential for development.


Figure 2. Forecast rain amounts from 92L from the 2am EDT Saturday run of the GFDL model. This model predicts most of 92L's heaviest rains will miss Haiti, but will affect Jamaica, the Cayman Islands, and the Yucatan Peninsula. Image credit: Morris Bender, NOAA/GFDL.

Igor
Tropical Storm Igor is very close to hurricane strength, and appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is moderate, 15 - 20 knots, waters are warm, 28°C, and Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor will track west under the influence of a strong ridge of high pressure for the next three days, then turn more to the west-northwest in response to the steering influence of a broad trough of low pressure moving across the Western Atlantic on Tuesday and Wednesday. This should allow Igor to pass several hundred miles to the northeast of the Lesser Antilles. In the longer range, Igor may be a threat to Bermuda, and has a slight chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 10% of all tropical cyclones that have existed at Igor's current position have gone on to hit the U.S. East Coast; these odds are about 10% for Bermuda and 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model shows a continuation of the pattern we've seen all hurricane season, with regular strong troughs of low pressure moving off the U.S. East Coast. This pattern favors Igor eventually recurving out to sea without affecting any land areas. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.

Elsewhere in the tropics
A new tropical wave (Invest 93L) emerged from the coast of Africa yesterday, and is already showing signs of organization. Most of the models predict 93L will develop into a tropical depression 2 - 4 days from now, and NHC is giving 93L a 30% chance of developing by Monday.

Next post
This may be my only post today; I'll have a new post Sunday morning.

Jeff Masters

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Quoting traumaboyy:
Good evening Chief, Kori, XCOOL....and gang!!


Good evening! Thanks for dropping by my blog. Much appreciated. :)
Member Since: March 7, 2007 Posts: 585 Comments: 20862
1171. pottery
JASON>>>
I am sorry. I cannot bear your caps anymore.
'bye.
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1170. JRRP

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1169. Relix
If Anything Igor is sightly north of the forecast points.
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1166. Relix
Quoting jacechase:
To me it looks like Igor is starting to move a bit south of due west, anyone else see that?


I think it was around this time we started this discussion last night haha
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1165. JRRP
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Quoting StormW:
Looks like 92L wants to fire some convection close to the supposed coc.
Member Since: October 9, 2008 Posts: 0 Comments: 8394
Quoting Neapolitan:


You're definitely going on my ignore list--in fact, I thought you were on it already, to tell you the truth--but I just have to ask as politely as I can before you go: do you realize that you have absolutely no idea what you're talking about? ;-)

I second that motion
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Quoting jacechase:
To me it looks like Igor is starting to move a bit south of due west, anyone else see that?


Yes as predicted by NHC
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Quoting traumaboyy:
Good evening Chief, Kori, XCOOL....and gang!!
Good evening Traumaboyy.
Member Since: October 9, 2008 Posts: 0 Comments: 8394
To me it looks like Igor is starting to move a bit south of due west, anyone else see that?
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Quoting anyotherliestotell:
sorry but a bunch of weak little TSs and a handful of storms out in the middle of the ocean is not an "active" season except in the most technical sense.


You're definitely going on my ignore list--in fact, I thought you were on it already, to tell you the truth--but I just have to ask as politely as I can before you go: do you realize that you have absolutely no idea what you're talking about? ;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13571
Member Since: July 9, 2006 Posts: 184 Comments: 29610
1154. Levi32
Quoting chsstormgirl:


Levi,
How reliable is the UKMET?


It's a decent model, about on the level of the GFS in terms of accuracy I would say, but not as good as the ECMWF.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
Good evening Chief, Kori, XCOOL....and gang!!
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1150. bassis
Is the broad structure of 92L a positive or negative come d-max?
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Quoting stormpetrol:
I think despite the lack of convection with 92l, I think it is well on the way to developing a closed circulation, anyway the next 24 hours will tell the tale, jmo.


Be careful with this one it looks like its trying to do something stupid, very suspicious!
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You know it's not good when the forecast discussion for Igor went from talk of a NW turn to barely any talk on any northerly component other then the fact it should turn WNW.
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Quoting Eugeniopr:


Please, you are right, but your comments are not good for the blog.


No he's wrong, he's dead wrong.

But whatever.
Member Since: July 8, 2005 Posts: 259 Comments: 24199
Quoting anyotherliestotell:
sorry but a bunch of weak little TSs and a handful of storms out in the middle of the ocean is not an "active" season except in the most technical sense.


And of course.. right on cue someone says that. I'd post the obvious, but I'm not in the mood to.
Member Since: July 8, 2005 Posts: 259 Comments: 24199
1145. xcool


92l wow


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Quoting Levi32:
Oh boy....the 500mb pattern over North America at Day 6 on the 12z UKMET is a big owwee in terms of Igor.

It has the polar vortex diving out of central Canada in such a way that would raise the heights to the east and take Igor farther west before recurving.



12z UKMET track is in blue with boxes:



Levi,
How reliable is the UKMET?
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Quoting gulfbreeze:
Why is everyone comparing 2005 to 2010, 2005 was a ones in a life time year?


What are you talking about? I see no one posting comparisons to 2005.
Member Since: July 8, 2005 Posts: 259 Comments: 24199
1141. xcool
Igor going ouut sea
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Quoting Eugeniopr:


Please, you are right, but your comments are not good for the blog.
Please don't feed the trolls.
Member Since: July 23, 2010 Posts: 1 Comments: 12414
Quoting StormW:
I would, pretty much, look for a slight shift left in model guidance.


Yes Sir; I concur i think some of the Models is showing this also only oh so slight as it may be.
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1137. xcool
AL, 92, 2010091200, , BEST, 0, 152N, 675W, 25, 1008, DB
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Quoting anyotherliestotell:
sorry but a bunch of weak little TSs and a handful of storms out in the middle of the ocean is not an "active" season except in the most technical sense.


Please, you are right, but your comments are not good for the blog.
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1135. xcool
WHXX01 KWBC 120036
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0036 UTC SUN SEP 12 2010

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL922010) 20100912 0000 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
100912 0000 100912 1200 100913 0000 100913 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 15.2N 67.5W 16.1N 69.6W 17.1N 71.8W 17.8N 74.0W
BAMD 15.2N 67.5W 15.9N 69.7W 16.5N 71.8W 17.1N 73.8W
BAMM 15.2N 67.5W 16.0N 69.8W 16.6N 72.1W 17.2N 74.4W
LBAR 15.2N 67.5W 16.4N 70.2W 17.5N 72.8W 18.7N 75.1W
SHIP 25KTS 32KTS 40KTS 52KTS
DSHP 25KTS 32KTS 40KTS 52KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
100914 0000 100915 0000 100916 0000 100917 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 18.4N 76.2W 19.7N 81.4W 20.9N 86.8W 22.1N 91.4W
BAMD 17.8N 75.7W 19.1N 80.2W 20.3N 85.3W 21.7N 89.7W
BAMM 17.9N 76.5W 19.0N 81.7W 20.2N 87.4W 21.5N 92.2W
LBAR 19.9N 77.1W 22.2N 80.1W 24.2N 82.1W 25.4N 81.9W
SHIP 65KTS 79KTS 92KTS 105KTS
DSHP 56KTS 65KTS 68KTS 52KTS

...INITIAL CONDITIONS...
LATCUR = 15.2N LONCUR = 67.5W DIRCUR = 290DEG SPDCUR = 17KT
LATM12 = 14.1N LONM12 = 64.1W DIRM12 = 287DEG SPDM12 = 16KT
LATM24 = 13.4N LONM24 = 61.6W
WNDCUR = 25KT RMAXWD = 60NM WNDM12 = 25KT
CENPRS = 1008MB OUTPRS = 1010MB OUTRAD = 175NM SDEPTH = S
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
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Quoting troy1993:
Here is Igor doing stand-up comedy

Igor: " So one this time I came off Africa and I was feeling really good and exicted and I was like oh you know what I am going to go visit my mother in Florida so I was crusing along the Atlantic until I get near Puerto Rico and all of a sudden this idiot named Mr.Trough is like " BAMM! BAMM!" sorry not today.

Igor needs to be fired from his standup routine
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Good structure...but....

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Quoting jacechase:
Stormw the envelope of 92l is also a nice size.


Good, more fun
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On this date, Hurricane Ivan hit the cayman islands as a Cat 4/5, occurring on the infamous 9/11 day.
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Quoting captainktainer:
Won't 92L's large size make it take much longer to spin up?

not necessarily
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I think despite the lack of convection with 92l, I think it is well on the way to developing a closed circulation, anyway the next 24 hours will tell the tale, jmo.
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Quoting troy1993:
Here is Igor doing stand-up comedy

Igor: " So one this time I came off Africa and I was feeling really good and exicted and I was like oh you know what I am going to go visit my mother in Florida so I was crusing along the Atlantic until I get near Puerto Rico and all of a sudden this idiot named Mr.Trough is like " BAMM! BAMM!" sorry not today.


I think Igor needs to stick with his day job...
Member Since: November 8, 2009 Posts: 4 Comments: 13571
Quoting StormW:
I would, pretty much, look for a slight shift left in model guidance.


Good, it will keep people in the blog.
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Stormw the envelope of 92l is also a nice size.
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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.