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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92l' center appears to be about a hundred miles south of the haiti/dr border,and looks to be moving nw,i wouldn't be suprised if it goes directly over jamacia...,
Member Since: Posts: Comments:
Quoting plywoodstatenative:
what the name of something is a yellow circle doing that far north in the Atlantic. Can you explain that, the area is not conducive to development as far as I can understand
Something was spinning out there on WV imagery last time I looked on Friday evening. NHC designated it an AOI yesterday, I suppose, but didn't expect much to come of it.
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Miami, cause thats the way the blog is.
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Seriously though, someone have a look at TD12 on the still off of Africa. I doubt it's a genuine eye. But, it's creepy.
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Quoting plywoodstatenative:
what the name of something is a yellow circle doing that far north in the Atlantic. Can you explain that, the area is not conducive to development as far as I can understand


I would think maybe subtropical in that location. NHC obviously thought it was worth monitoring.
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241. MZT
Quoting PensacolaDoug:
MZT is losing the bubble...


Yeah, I should go finish painting. It's nice enough out. These storms will still be here at 5PM
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Quoting WeatherNerdPR:
Ok, so Igor's a Cat2 in the Central Atlantic still moving westward. For how much longer will he keep moving in that direction?

I'm 90% sure 2 days at most and hoping to see a solid trend north starting tomorrow night per the GFS model.
I'm in St Thomas and right now with the Sat pics showing the trough that is supposed to re-curve igor northward in place although not extending as far south as I'd like I can't see igor not starting to head more NW in the the next 2 days.

Earl got kept south and pushed west more than th e models initially predicted because a strong extra tropical low reinforced the ridge. That is not happening this time.
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239. txjac
Quoting sopla2o:
Will the fact that Igor makes it to a Cat 4 or 5 for that matter, affect the track. Is there any relationship between the size of the storm and the track.



Good question as its one that I have as well. Thanks for asking
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Quoting HurricaneIsabel:
If this is another earl then that's a good thing, earl was a fish storm LOL! ....(Awaits to get told that this was not a fish storm)


It was fish for the USA.
Canada got the eye come ashore just south of where I am.
1 person dead.
1,000,000 fish spun around in circles.

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OK. I think we all agree now that TD12 and 92L are not the same. We can relax now.
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Quoting MZT:
TD12. Africa. Not Caribbean.

She was speaking about 92L. Jeez, why do you need to have a discussion about something so simple?
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Quoting MZT:
TD12. Africa. Not Caribbean.



She never said TD12.

92L is an invest in the Caribbean.
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You ARE absolutely correct stormwatcherCI, the NHC is confused or plate tectonics have taken a big leap forward! Soon we will have the long awaited land bridge from Africa to Florida via the Antilles!!!!
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what the name of something is a yellow circle doing that far north in the Atlantic. Can you explain that, the area is not conducive to development as far as I can understand
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230. MZT
deleted. OK. I can't read today.
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Quoting Stormchaser2007:


Yep.

You were right.
Thank you.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Quoting sopla2o:
Will the fact that Igor makes it to a Cat 4 or 5 for that matter, affect the track. Is there any relationship between the size of the storm and the track.
It could "pump the ridge", which would cause it to go further north and west, rather then just recurve out to sea.
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227. txjac
Quoting BahaHurican:
That's one goodlooking storm....



I agree...amazing to me that something so beautiful can be so deadly

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Quoting stormwatcherCI:
For all those people who think I have lost my mind. I do know the islands in the Caribbean and never knew Hispaniola was off the coast of Africa. Please take a look at the image I posted again. It is 92L NOT TD12.


Yep.

You were right.
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Quoting Stormchaser2007:
Igor the Al Gore sized system

00z NCAR WRF

The Eye is bigger than Rhode Island!
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Quoting MiamiHurricanes09:
I'll pick the first option...for now.

That's good to hear, but I don't wanna be here if that doesn't happen.
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Quoting stormwatcherCI:


92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.

I see it.
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222. 7544
igor maybe be south of the next fcst point ?
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This is the first in a while that I've seen which might potentially aspire to the label "annular". NOT saying it's that way now, mind u....
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Igor the Al Gore sized system

00z NCAR WRF

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Will the fact that Igor makes it to a Cat 4 or 5 for that matter, affect the track. Is there any relationship between the size of the storm and the track.
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Quoting Stormchaser2007:
Flirting with 6.0


Final T# Adj T# Raw T#
5.9 6.0 6.0



"Flirting" lol.
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Quoting WeatherNerdPR:

Hi MH09. Do you think it'll harmlessly recurve out to sea, or will he do something else?
I'll pick the first option...for now.
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For all those people who think I have lost my mind. I do know the islands in the Caribbean and never knew Hispaniola was off the coast of Africa. Please take a look at the image I posted again. It is 92L NOT TD12.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
215. beell
ATL WV Loop
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214. 7544
is 92l drifting wnw
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Flirting with 6.0


Final T# Adj T# Raw T#
5.9 6.0 6.0


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MZT is losing the bubble...
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Quoting Stormchaser2007:


???

" 92L looks like it is wrapping convection around a coc at approximately 72.2W/16N."
The floater says AL12 but still showing 92L.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Quoting MZT:

Not unless it has learned teleportation.

TD12 IS OFF THE COAST OF AFRICA


That would be former 93L.

92L is in the Caribbean.
Member Since: July 6, 2010 Posts: 113 Comments: 32275
Quoting MZT:

Not unless it has learned teleportation.

TD12 IS OFF THE COAST OF AFRICA
Quoting Stormchaser2007:


???

92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.

Heh.
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Quoting Stormchaser2007:


???

92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.


Amazing how people don't read what they write, and then they yell at you.
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Quoting MZT:

Not unless it has learned teleportation.

TD12 IS OFF THE COAST OF AFRICA
I know TD 12 is off the coast of Africa but if you look at the surrounding area this is 92L with Hispaniola to the north.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
That's one goodlooking storm....

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Quoting Stormchaser2007:


???

92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.
92l is in the carribean
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Quoting MZT:


Not unless it has learned teleportation.

TD12 IS OFF THE COAST OF AFRICA


???

" 92L looks like it is wrapping convection around a coc at approximately 72.2W/16N."
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Quoting MiamiHurricanes09:
If it continues to undergo rapid intensification, it will likely achieve major hurricane status by the end of the day.



Very impressive eyewall.


Hi MH09. Do you think it'll harmlessly recurve out to sea, or will he do something else?
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201. MZT
Quoting stormwatcherCI:
92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.

Not unless it has learned teleportation.

TD12 IS OFF THE COAST OF AFRICA
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ST2007

That could be a candidate for the A word down the line.
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Quoting BahaHurican:
I'm not impressed right now by the look of that second trough, which IMO will need some amplification to make itself felt for any long period of time.

What, if anything, is likely to be out there past 5 days as a potential 3rd blow to Igor? The CONUS looks pretty devoid of activity west of the Mississippi right now....


It def looks like he may cut it close
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Quoting stormwatcherCI:


92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.


yes
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Yep.Looks like my nickname is coming into use after all."Impressive Igor" it is.So far his name has been something to fear.
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Quoting MiamiHurricanes09:
If it continues to undergo rapid intensification, it will likely achieve major hurricane status by the end of the day.



Very impressive eyewall.





UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 141500 UTC
Lat : 17:38:51 N Lon : 45:21:28 W


CI# /Pressure/ Vmax
5.9 / 952.4mb/112.4kt


Final T# Adj T# Raw T#
5.9 6.0 6.0

Latitude bias adjustment to MSLP : +2.0mb

Estimated radius of max. wind based on IR : 26 km

Center Temp : +7.4C Cloud Region Temp : -64.7C

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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.