92L still a threat to develop; Igor a hurricane; TD 12 forming near Africa

By: Dr. Jeff Masters , 2:18 PM GMT on September 12, 2010

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Tropical disturbance (92L) over the Central Caribbean, a few hundred miles south of the Dominican Republic, remains a threat to develop into a tropical depression. Satellite loops this morning show 92L may be starting to form a surface circulation, and an Air Force Hurricane Hunter aircraft will investigate 92L this afternoon to see if a tropical depression is forming.

The storm has only a modest area of heavy thunderstorm with limited low-level spiral banding and upper-level outflow, thanks to an infusion of dry air last night that disrupted the storm. Long range radar out of Puerto Rico shows that heavy rains are affecting that island, but there is no rotation to the radar echoes evident. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are hot, 29.5°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 to west-northwest at 15 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 Belize or Mexico's Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches today through Monday morning; southern Haiti can expect similar rains tonight through Monday night, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba can expect rains in the 2 - 4 inch range. Once 92L crosses the Yucatan, the ridge of high pressure steering it is expected to remain in place, forcing 92L to a second landfall in Mexico south of the Texas border.

Intensity forecast for 92L
NHC is putting the odds of 92L developing into a tropical depression by Tuesday at 50%; I'd put them higher, at 70%. However, time is running out for 92L to become a hurricane before hitting the Yucatan Peninsula on Wednesday. Given the current disorganized state of 92L, it would be difficult for it to intensify quickly enough to become a hurricane by then. The storm may also suffer another of its mysterious evening collapses, where it loses most of its heavy thunderstorm activity. However, the SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and 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. There are a number of research flights being made into 92L this afternoon that should help long-term efforts to make better predictions in the future on whether or not disturbances like this will develop or not.


Figure 2. Morning satellite image of Igor.

Igor
Hurricane Igor appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is low, 5 - 10 knots, and is expected to drop below 5 knots for the next five days. Waters are warm, 28°C, and will warm to 29°C by Wednesday. Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor is undergoing a period of rapid intensification today, and will probably be a Category 3 or 4 hurricane by Monday.

The track forecast for Igor remains unchanged. Igor will move west under the influence of a strong ridge of high pressure for the next 2 - 3 days, then turn more to the west-northwest then 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 does have a small chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 15% 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 10% for Canada. The forecast steering pattern for the period 5 - 12 days from now from the ECMWF and GFS models 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. Recent runs of the ECMWF model indicate that these troughs may not be as intense as previously thought, so it is possible Igor has a higher chance than usual to hit land than climatology suggests. One wild card may be the possible development of TD 12 behind Igor. If TD 12 develops into a hurricane, and moves close to Igor, as some of the models are suggesting, the two hurricanes could rotate around a common center, forcing Igor more towards the coast of the U.S. The long term fate of Igor is difficult to predict at this point.

Tropical Depression Twelve forms
Tropical Depression Twelve formed between the Cape Verdes Islands and coast of Africa this morning, and is already affecting the Cape Verdes with winds near tropical storm strength; sustained winds of 35 mph were recorded in the northwest Cape Verdes this morning. You can follow the progress of TD 12 through the Cape Verdes today using our wundermap.

Next post
I'll have a new post Monday morning, and perhaps late this afternoon if events warrant.

Jeff Masters

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Looks like some dry shear is coming from the east upsetting 92L. The Caribbean isn't usually this dry is it?
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Quoting AtHomeInTX:


Not sure if it's breaking down but I've read a couple things now where it's moving east. So that would allow 92L to take more of a northern track. Don't know how far north but keeping an eye on it.


indeed......
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Quoting Kearn:
Power lines exploding in upper FL... big blue flashes in the sky
Frontal squall line?
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Member Since: August 11, 2010 Posts: 0 Comments: 895
Quoting TOMSEFLA:
recon has found ssw winds so far
Can you please show me how you know this ?
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Quoting sunlinepr:
Igor, Julia and the next one......


My kids rolled on this one. Cute! LOL
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2490. Drakoen
Quoting Stormchaser2007:


Updated off of the SSD ADT site.

6.7 now. Could he rise to 7.0?

2010SEP12 234500 6.7 931.4/ +2.0 /132.2 6.7 6.9 6.9


Impressive. 7.0 is possible if the cloud top temperatures in the eyewall cool some more or the temperature in the eye warms.
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Quoting TexasHurricane:


Is that high breaking.....hmmmmmmm


Not sure if it's breaking down but I've read a couple things now where it's moving east. So that would allow 92L to take more of a northern track. Don't know how far north but keeping an eye on it.
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Quoting MZT:
If the pressure goes under 930mb we're going to be in the "why isn't it CAT5" territory...

Sheesh, and this time of the evening is normally the diurnal minimum.


diurnal impacts almost never apply to storms of this strength
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Sorry, Julia is on the way....

Quoting Zorfwaddle:
Julia??

I see Igor, TD12 and 92L, but no Julia. Where the heck is that one??

This is to remind folks that novices/ interested parties like me do not like to deal with folks making presumptions.

Get a grip.

Not a troll, just a gripe...

George
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Nice analysis Kori!
Member Since: September 10, 2007 Posts: 0 Comments: 11104
Quoting kimoskee:


WHAT!!! I can't believe that!!!
Just Check out the hurricane hunter as it is in the system right now
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2484. Max1023
The raw T#'s at 6.9 which have been seen state that Igor has reached Category 5 status, as Category 5 begins at 136 knots as opposed to 140 knots. T# 6.9 is about 137.4 Knots.
Member Since: July 22, 2008 Posts: 1 Comments: 286
2483. MZT
If the pressure goes under 930mb we're going to be in the "why isn't it CAT5" territory...

Sheesh, and this time of the evening is normally the diurnal minimum.
Member Since: September 24, 2005 Posts: 0 Comments: 793
Super Job man.... Keep it going...

Quoting KoritheMan:
Hey guys, I just wrote a blog on Igor, TD12, and 92L. I put a lot of effort into it. Tell me what you think!
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Quoting Drakoen:
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 231500 UTC
Lat : 17:39:45 N Lon : 47:05:37 W


CI# /Pressure/ Vmax
6.6 / 934.2mb/129.6kt



Final T# Adj T# Raw T#
6.6 6.7 6.7

Latitude bias adjustment to MSLP : +2.0mb

Estimated radius of max. wind based on IR : 25 km

Center Temp : +16.0C Cloud Region Temp : -71.2C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT

Weakening Flag : OFF
Rapid Dissipation Flag : OFF


Updated off of the SSD ADT site.

6.7 now. Could he rise to 7.0?

2010SEP12 234500 6.7 931.4/ +2.0 /132.2 6.7 6.9 6.9
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Quoting surfsidesindy:


Ukmet was doing that last night. Those kind of things don't give you warm fuzzies...


No, it sure doesn't. Go read Levi's latest blog. That will even make you feel worse.
Member Since: August 18, 2008 Posts: 0 Comments: 884
Kearn... pretty quiet here tonight... hope we don't get ur stuff anytime soon. That does not sound conducive to the health of anything u have plugged in....
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2478. angiest
Quoting Kearn:
Power lines exploding in upper FL... big blue flashes in the sky


Come on now, Igor isn't *that* strong... ;D
Member Since: August 26, 2006 Posts: 16 Comments: 4766
recon has found ssw winds so far
Member Since: October 19, 2005 Posts: 0 Comments: 234
Julia??

I see Igor, TD12 and 92L, but no Julia. Where the heck is that one??

This is to remind folks that novices/ interested parties like me do not like to deal with folks making presumptions.

Get a grip.

Not a troll, just a gripe...

George
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2475. dmaddox
Quoting Kearn:
Power lines exploding in upper FL... big blue flashes in the sky
huh?
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Igor, Julia and the next one......
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2473. Kearn
Power lines exploding in upper FL... big blue flashes in the sky
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Quoting KoritheMan:
Hey guys, I just wrote a blog on Igor, TD12, and 92L. I put a lot of effort into it. Tell me what you think!


Excellent job!

Mind if I email this to a few people to let them know whats going on?
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Quoting belizeit:
WOW they found a center in 92L


WHAT!!! I can't believe that!!!
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2464. Shows a 150mph Hurricane just on the cusp of Cat 5.
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I can see I may have to update my blog tomorrow.

Say, what do u think r the chances future Julia will make it all the way across the ATL before recurving.... huh? LOL [just for laffs]
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Quoting MiamiHurricanes09:
I think Igor is a category 5 hurricane right now.

why dosent the NHC do a special advisory? it might not be a cat. 5 by the time 11pm rolls around
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2467. JLPR2
Quoting TexasHurricane:


Is that high breaking.....hmmmmmmm


That's true, I expect the turn, but not that sharp.
Member Since: September 4, 2007 Posts: 7 Comments: 8662
2466. dmaddox
the season so far:
Member Since: Posts: Comments:
2464. Drakoen
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 231500 UTC
Lat : 17:39:45 N Lon : 47:05:37 W


CI# /Pressure/ Vmax
6.6 / 934.2mb/129.6kt



Final T# Adj T# Raw T#
6.6 6.7 6.7

Latitude bias adjustment to MSLP : +2.0mb

Estimated radius of max. wind based on IR : 25 km

Center Temp : +16.0C Cloud Region Temp : -71.2C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT

Weakening Flag : OFF
Rapid Dissipation Flag : OFF
Member Since: Posts: Comments:
I sure hope that 92L ain't one those that bite you in the back when you least expect it.
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Quoting SSideBrac:
Pilot Guy & StormwatcherCI - ty
You're welcome. It definitely looks like it is making an extra effort tonight. Convection is consolidating at the "COC" but I guess it is still a wait and see.
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Quoting KoritheMan:
Hey guys, I just wrote a blog on Igor, TD12, and 92L. I put a lot of effort into it. Tell me what you think!


Great Job!!
Member Since: August 11, 2010 Posts: 0 Comments: 895
2459. 1965
A kernel of global model support for a CONUS strike by Igor.

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2458. lennit
this a bad time of year.. remember Ike was supposed to turn out.. then was supposed to hit e coast of Fl then . we all know what happened. just keep updated until he is gone
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WOW they found a center in 92L
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2456. dmaddox
we're on the home stretch! LOL
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Quoting AtHomeInTX:


SmileyCentral.com


:) ..... where do you get those?
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Quoting JLPR2:


It is supposed to keep moving west till 49-50W


Yes, but notice the flow in front of Igor is due west all the way to 60 west. We better hope the trof does its job!
Member Since: August 11, 2010 Posts: 0 Comments: 895
Quoting AtHomeInTX:
Houston

DURING THE MIDDLE AND LATE
WEEK PERIOD...THE RIDGE WILL DRIFT OVERHEAD AND THEN EAST OF THE
AREA.
BY THE END OF THE WEEK THE GFS AND ECMWF DIFFER ON THE
DEVELOPMENT AND MOVEMENT OF A POSSIBLE TROPICAL CYCLONE ACTIVITY
OVER THE SOUTHERN GULF OF MEXICO.

Hate when that happens.


Is that high breaking.....hmmmmmmm
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Member Since: September 2, 2009 Posts: 130 Comments: 21122
Quoting JLPR2:


It is supposed to keep moving west till 49-50W


We really hope that will be the right model Igor follows.... Else there will be no surfing in PineGrove....
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I think Igor is a category 5 hurricane right now.
Member Since: September 2, 2009 Posts: 130 Comments: 21122
2448. bassis
Quoting btwntx08:
remember its moonsoonal development


Lol A feature of a D-Waxing moon
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Quoting want2lrn:


That will be enough of that ATHOME!


SmileyCentral.com
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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.

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