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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Quoting Neapolitan:


I'm terribly sorry you're so bored; by all means, please continue to limit yourself from coming here. ;-)


++++++++++
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795. DDR
Quoting pottery:
In the Meantime....
an afternoon thunder-thingy is building overhead here, with fireworks and cymbal-noises approaching.

I will be back, after I attack a large portion of cheese-cake I just remembered in the fridge...

Hey,tell me about it!
Its been raining by the buckets for an hour an a half,possibly some floding going right now
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Quoting Ameister12:
This is 100% not a category 2 anymore.

Probably a low end CAT 4 w/135MPH winds, w/min central pressure around 945mb!!!!
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I think it's nearing moderate CAT 4 strength 140-145MPH

the eye isn't completely clear, and the structure isn't completely perfectly circular for it to be a CAT 5 but it can get there by tonight especially with DMAX just giving it even more fuel
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I hope this thing stays away from any land mass. Looks really peeved right now. Over open water its a beautiful show.
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IGOR is BAAAD!
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Repost......

Afternoon StormW... I'm sitting here watching the Dolphins game (big fish fan here) and was reflecting on all that preaching you did this year... Looks to be coming to fruition my friend. Starting to look ominous out in the Atlantic and with all of that heat potential out there (even with some of it released into the Russian heat wave and Europe) Looks like this season could be a 2005 type season (not in number of storms) in length of season.. Everything is so hot storms are turning into tropical situations as soon as they dip thier toe in the water from Africa.... Hope we can keep dodging bullets here in Florida but with the patterns setting up the way they seem Im thinking the clock is ticking on us here in the South East.
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Quoting CosmicEvents:
That's why I suggested that next time around they go with something like Isaiah, or even Ishkabble.


Yo, they've got Isias lined up for 2014, that's the name they used to replaced Ike.

http://www.nhc.noaa.gov/aboutnames.shtml

Thats really close to Isaiah.
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Quoting Chicklit:
Cracks me up that every time a hurricane forms, someone asks if it's annular.
"Annular hurricanes are very rare."

Please see wiki article on them below.
annularhurricane


Well, Igor could very well be becoming annular, there isn't a need for snark here.
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Igor is 100% not a category 2 anymore.
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Quoting Drakoen:


No because you have an incoming trough


An incoming trough that looks flattening.
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Quoting TropicalAnalystwx13:


LMAO!

I was scrolling down the page, reading, and that scared me. it made me jump!

LMAO!


LOL

My bad.
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Quoting HurricaneSwirl:


92L got upped to 90% last night? Now it's all the way down to 50%
No, that was 93L...got upped to 12L this morning.
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Quoting StSimonsIslandGAGuy:
Maybe the NHC will issue a special advisory, although I don't see the need for it. Last night the NHC issued a special Tropical Weather Outlook to raise the probability of development for 92L to 90% at 11 pm and I didn't see the necessity for that either.

Igor is looking like a Cat 4 to me.


92L got upped to 90% last night? Now it's all the way down to 50%
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Quoting Stormchaser2007:


LMAO!

I was scrolling down the page, reading, and that scared me. it made me jump!

LMAO!
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Quoting MiamiHurricanes09:
SHIPS. Should come out in 30 minutes.
Quoting Stormchaser2007:


SHIPS
Oh, right. *smack*
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703. KanKunKid LOL
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Cotillion that is about as perfect a major storm as you can get.
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Quoting CybrTeddy:
Miami, when do the T# come out?
Around the same time as the SHIPS text...30 minutes or so.
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Comrade Igor

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Quoting NOLALawyer:


Because this seasons sucks, lacks excitement and has been painful to watch...especially watching CV storms traverse the entire Atlantic to recurve at the last minute. I have had to limit myself from coming here because these storms, and the frustration, tension and nervousness which they spawned in my psyche, were consuming me.

YMMV.


I'm terribly sorry you're so bored; by all means, please continue to limit yourself. ;-)
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Really, little banding apparent. (Less than I saw a bit ago)

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Miami, when do the T# come out?
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Quoting Cotillion:

Igor defiantly starting to look like Daniel.
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Quoting Levi32:
The ECMWF starting to show northwest movement of 92L in the Bay of Campeche is a big clue to Igor's track. The Euro was showing south of west movement in the BOC with 92L just a couple days ago. If the storm instead fades northwest, that implies more of a trough digging into the west-central US which would force the Texan ridge to build further east, implying a more westerly track for Igor and a more northerly one for 92L.


Sounds like the caribbean islands need to sit up and take note
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Quoting WeatherNerdPR:

2009 gave us a break, though.

Don't forget Ike..
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Quoting atmoaggie:
I forget, which of the text advisories has the annular flag in it?

Anyone?


SHIPS
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Quoting atmoaggie:
I forget, which of the text advisories has the annular flag in it?

Anyone?
SHIPS. Should come out in 30 minutes.
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Quoting StormW:
Levi, great update!

As (mets), couldn't ask for a prettier storm to look at this season.


Thanks Storm! Same to you.

Yes...Igor is eye-candy to us Mets right now.
Member Since: November 24, 2005 Posts: 635 Comments: 26749
92l looks like its going to take a hwrf like path towards haiti/se cuba area,also sustaining convection,though no closed surface low yet,still waiting on west winds,probably a td at some point tonight
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I forget, which of the text advisories has the annular flag in it?

Anyone?
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Quoting Seastep:


Correct me if I am wrong, but I though the CMC performed best last year at 5 days.

Have no idea about this year. Link to that would be appreciated if anyone has it.

I think CyberTeddy posted it before?


Ya the CMC can have some good accuracy on track once it has locked on, but early in the game it can be rather foolish.
Member Since: November 24, 2005 Posts: 635 Comments: 26749
Quoting Stormchaser2007:




WOW! WOW-WOW-WOW-WOW!!!!

(one for each image that was posted of Igor....but this one hit me the most)
Member Since: October 21, 2007 Posts: 27 Comments: 329
Igor is probably a category 4 now. (135 mph)
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In the Meantime....
an afternoon thunder-thingy is building overhead here, with fireworks and cymbal-noises approaching.

I will be back, after I attack a large portion of cheese-cake I just remembered in the fridge...
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Igor is an example of what could be an annular hurricane
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Quoting MiamiHurricanes09:
Igor might be Isabel's little brother. I gotta say, all these "I" names always have to be bad...

First Isabel, then Ivan, now Igor.
That's why I suggested that next time around they go with something like Isaiah, or even Ishkabble.
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747. Vero1
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN SEP 12 2010

...SPECIAL FEATURES...

THE CENTER OF HURRICANE IGOR AT 12/1500 UTC IS NEAR 17.7N 45.7W.
IGOR IS MOVING WESTWARD 11 KT.
THIS POSITION IS ABOUT 1145 MI...
1840 KM E OF THE NORTHERN LEEWARD ISLANDS. THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 970 MB. THE MAXIMUM SUSTAINED WIND SPEEDS
ARE 90 KT WITH GUSTS TO 110 KT.
PLEASE READ THE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/
WTNT31 KNHC AND THE FULL FORECAST AND ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. NUMEROUS STRONG
STRONG CONVECTION IS WITHIN 60 NM OF THE CENTER. IN ADDITION
SCATTERED MODERATE CONVECTION IS FROM 15N-19N BETWEEN 43W-47W.

THE CENTER OF TROPICAL DEPRESSION TWELVE AT 12/1800 UTC IS NEAR
13.1N 22.2W. T.D. TWELVE IS MOVING WESTWARD 12 KT.
THIS POSITION
IS ABOUT 190 MI...305 KM SE OF THE SOUTHERNMOST CAPE VERDE
ISLANDS. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. THE
MAXIMUM SUSTAINED WIND SPEEDS ARE 30 KT WITH GUSTS TO 40 KT.

PLEASE READ THE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT2/ WTNT32 KNHC AND THE FULL FORECAST
AND ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR
MORE DETAILS. WIDELY SCATTERED MODERATE CONVECTION IS FROM
11N-17N BETWEEN 20W-26W.

A 1007 MB LOW PRESSURE CENTER IS NEAR 16N72W...ABOUT 120 NM
SOUTH OF HISPANIOLA.
LOCALLY HEAVY RAINFALL IS OVER PUERTO
RICO...AND HISPANIOLA THAT MAY CAUSE LIFE-THREATENING FLASH
FLOODS AND MUD SLIDES..
.ESPECIALLY IN MOUNTAINOUS TERRAIN.
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 13N-19N BETWEEN
70W-76W...AND FROM 17N-21N BETWEEN 66W-70W. IT IS POSSIBLE THAT
A TROPICAL DEPRESSION MAY FORM DURING THE NEXT 48 HOURS.
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Quoting tropicfreak:


Don't forget Ike!


When you are in an above-average year (ever since the warm AMO kicked in during 1995), its the F,G,H,and I names that have the biggest risk it seems of being a major storm because you've gone through more storms by the time you are at the peak (Sept. 10) of the season.

In years that are below-average (cold AMO years), it seems anywhere from A to E is usually the big storm.
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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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