92L still a threat to develop; Igor a hurricane; TD 12 forming near Africa
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
Reader Comments
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10-0 baby now
First Isabel, then Ivan, now Igor.
Yes
It has to be.
Why isn't the NHC making a Special Advisory (SA)
WHY WHY WHY?!?!?
I'm through...lol
Wouldn't the massive high pressure per the CMC push any storm into Florida and then into the GOM? Granted if that scenario would have to materialize.
Does that mean that the wave still has a "low" in it? (not sure if I'm making sense)
Last run of ECMWF I saw this morning did have it brushing the Eastern seaboard ala Earl
Well, its nowhere near land, so issuing a special advisory doesn't seem needed. But, I am not so sure about Igor being a cat. 4 just yet. Its possible it will be that this evening (right now its probably a cat. 3).
Darn, I didn't foresee this rapid of an intensfication in my forecast last night. Intensity forecasting is hard!
2009 gave us a break, though.
"Annular hurricanes are very rare."
Please see wiki article on them below.
annularhurricane
Levi,
If the high that is protecting the TX/LA coast right now bridges with the other, will that move the high off the TX/LA coast?
Yes
I knew it, Igor was destined to be a strong hurricane from an African tropical wave all along! Its an appropriate name for a beast of a Cape Verde hurricane. Its perfect, LOL
It would be centered more off to the east, which would open the door for 92L to make a move closer to Texas instead of Mexico.
Don't forget Ike!
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.
WOW I love mimic
Oh don't worry.
I think I have successfully given myself carpal tunnel.
Here's the link to my account if anyone is interested.
Toilet Paper War?
No because you have an incoming trough
Don't forget Ike
wow
Back to lurking. God bless!
Hey Cycloone! Long time no see!
Man, 947MB is like going up 2500 feet in altitude. We're getting into some serious pressure gradients here.
Engineering Toolbox: Air Pressure
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?
Thank you.
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.
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.
Viewing: 701 - 751
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