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 TropicalAnalystwx13:
Earl's a Cat. 4!


The only word that popped into my head was "DUH!" lol

He's looking all kinds of fine out there. I'm hoping and praying he stays far away from land. I don't think he will right now, but I'm sure has heck hoping he will!
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Quoting tropicfreak:


You mean Igor.


Yes, yes I do.
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In a way, be nice if Igor did become annular.

Hopefully get some really nice observations with the new gadgetry they have.

Been 4 years since the last one (Daniel, EPAC).

And is it mean to laugh liberally at the Bengals?
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Quoting TropicalAnalystwx13:
Earl's a Cat. 4!

Earl! XD
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Special advisory out, Igor now a category 4 hurricane.

...IGOR RAPIDLY INTENSIFIES INTO A CATEGORY FOUR HURRICANE...
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IGOR 950 cat4 - ALEX Cat2 at 947....

Odd......
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000
WTNT31 KNHC 121806
TCPAT1
BULLETIN
HURRICANE IGOR SPECIAL ADVISORY NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
230 PM AST SUN SEP 12 2010

...IGOR RAPIDLY INTENSIFIES INTO A CATEGORY FOUR HURRICANE...


SUMMARY OF 230 PM AST...1830 UTC...INFORMATION
----------------------------------------------
LOCATION...17.7N 46.1W
ABOUT 1120 MI...1800 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...135 MPH...215 KM/HR
PRESENT MOVEMENT...W OR 270 DEGREES AT 14 MPH...22 KM/HR
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES





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Any updates since the 1645Z CIMSS update est of 947MB/T 6.4 and 117KTS???
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Quoting MiamiHurricanes09:
Awesome! The image is almost 3 hours old though.


Yeah, that was the point lol

Was trying to show that this could have been a phase of RI.
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The NHC is calling it Igor a 135mph Cat 4 right now...
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Quoting TropicalAnalystwx13:
Earl's a Cat. 4!


You mean Igor.
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000
WTNT31 KNHC 121806
TCPAT1
BULLETIN
HURRICANE IGOR SPECIAL ADVISORY NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
230 PM AST SUN SEP 12 2010

...IGOR RAPIDLY INTENSIFIES INTO A CATEGORY FOUR HURRICANE...


SUMMARY OF 230 PM AST...1830 UTC...INFORMATION
----------------------------------------------
LOCATION...17.7N 46.1W
ABOUT 1120 MI...1800 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...135 MPH...215 KM/HR
PRESENT MOVEMENT...W OR 270 DEGREES AT 14 MPH...22 KM/HR
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 230 PM AST...1830 UTC...THE CENTER OF HURRICANE IGOR WAS LOCATED
NEAR LATITUDE 17.7 NORTH...LONGITUDE 46.1 WEST. IGOR IS MOVING
TOWARD THE WEST NEAR 14 MPH...22 KM/HR. A TURN TOWARD THE
WEST-NORTHWEST IS EXPECTED ON TUESDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 135 MPH...215 KM/HR...WITH HIGHER
GUSTS. IGOR IS A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON
HURRICANE WIND SCALE. SOME ADDITIONAL STRENGTHENING IS FORECAST
DURING THE NEXT 48 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 40 MILES...65 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 160
MILES...260 KM.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 950 MB...28.05 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 PM AST.

$$
FORECASTER ROBERTS/BRENNAN



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00
WTNT31 KNHC 121806
TCPAT1
BULLETIN
HURRICANE IGOR SPECIAL ADVISORY NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
230 PM AST SUN SEP 12 2010

...IGOR RAPIDLY INTENSIFIES INTO A CATEGORY FOUR HURRICANE...


SUMMARY OF 230 PM AST...1830 UTC...INFORMATION
----------------------------------------------
LOCATION...17.7N 46.1W
ABOUT 1120 MI...1800 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...135 MPH...215 KM/HR
PRESENT MOVEMENT...W OR 270 DEGREES AT 14 MPH...22 KM/HR
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

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Earl's a Cat. 4!
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It's true, everytime a Cat3 or higher that's ever come down the pike for the last 6 years this blog has thrown around the annular word.
.
.
So, please enlighten me. What would it mean right now if Igor was declared an annular hurricane? Besides being something of interest for mets. Would it effect track, intensity, etc?
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Quoting Levi32:
Out 'til later.

Tropical Tidbit for Sunday, August 12th


Thanks for the update Levi. Have a good one and see ya later.
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Quoting DDR:

Hey,tell me about it!
Its been raining by the buckets for an hour an a half,possibly some floding going right now

Heh!!
Just started here.
Coming in from the NW.
Your gully must be noisy....
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Quoting StormW:


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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.


Great update Levi. If your crazy Japanese model scenario pans out you should be Met. of the year!
Member Since: August 4, 2010 Posts: 0 Comments: 166
Quoting Bordonaro:

Probably a low end CAT 4 w/135MPH winds, w/min central pressure around 945mb!!!!

I totally agree with you.
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Quoting Ameister12:

I totally agree with you.

By 5PM AST, Igor may have 145MPH winds and a minimum central pressure of 935MB..Looks beautiful..
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Quoting Bordonaro:

Probably a low end CAT 4 w/135MPH winds, w/min central pressure around 945mb!!!!

I totally agree with you.
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Quoting Stormchaser2007:
Sweet! RAMMB added AVHRR.

Hot-towers in the eye?

Awesome! The image is almost 3 hours old though.
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Quoting Stormchaser2007:
Sweet! RAMMB added AVHRR.

Hot-towers in the eye?


Wow!
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Probably a low end CAT 4 w/135MPH winds, w/min central pressure around 945mb!!!!


And ALEX was a medium cat2 @ 947? Homey don't think so!
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Out 'til later.

Tropical Tidbit for Sunday, August 12th
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting Chicklit:
IGOR is BAAAD!


Wow! He truly is. Let's just hope he recurves and follows his brothers and sisters into the North Atlantic to visit Iceland. Yikes.
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Quoting StormW:


Igor's going nuts! Wow that looks good. Maybe I'll have to give up and jump on the bandwagon that says its a cat. 4 right now instead of cat. 3. One thing's for sure, this is our third major hurricane this season.
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Quoting Bordonaro:

Probably a low end CAT 4 w/135MPH winds, w/min central pressure around 945mb!!!!

I totally agree with you.
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Sweet! RAMMB added AVHRR.

Hot-towers in the eye?

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All NOAA Tropical Floater Imagery
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Some characteristics of an Annular cyclone. This microwave pass from an hour ago reveals no spiral banding, but it does show a small tight core.

Member Since: October 28, 2006 Posts: 57 Comments: 30490
Quoting FloridaTigers:


Well, Igor could very well be becoming annular, there isn't a need for snark here.

snark? you gotta admit...there's always the annular comment. just stating the obvious.
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Igor will likely become the strongest and first Category 5 storm since Dean in 2007.
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O Lordy..

LOL
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Quoting Levi32:


Thanks Storm! Same to you.

Yes...Igor is eye-candy to us Mets right now.


Trust me, there is many non-Met weather-geeks that are drooling looking at him too! lol Myself included!! :D
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Quoting NCHurricane2009:


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.
Thank you
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IGOR lookin good, like the 'FINS!
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Quoting Seflhurricane:
dear god that is one monster approaching the central bahamas !!!!!!!!!!
U know, u could have NOT said that.......

Hoping CMC is on crack 2day.... especially since this is 12z and not one of the more suspect "interim" runs....

Quoting StSimonsIslandGAGuy:
I also think that Igor may become the first true annular hurricane in the Atlantic since Isabel.
Yeah, was thinking this earlier this morning when I saw that very solid structure even though cloud tops had not yet cooled to where they are now...

Quoting hurricane23:
Anything is possible but i doupt the 12z CMC comes even close to verifying.
Thank u for ur support.... lol Really REALLY not liking even the idea of that right now.

Quoting Levi32:
Freaking Beautiful.

Like, that's why I haven't changed my avatar.... like the most beautiful storm of our time... lol

Want to see if Igor can match that.
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.