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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Is that high breaking.....hmmmmmmm
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!
:) ..... where do you get those?
Great blog!!!
Great Job!!
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
Very nice, Kori!
That's true, I expect the turn, but not that sharp.
why dosent the NHC do a special advisory? it might not be a cat. 5 by the time 11pm rolls around
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]
WHAT!!! I can't believe that!!!
Excellent job!
Mind if I email this to a few people to let them know whats going on?
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
Come on now, Igor isn't *that* strong... ;D
No, it sure doesn't. Go read Levi's latest blog. That will even make you feel worse.
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
Sheesh, and this time of the evening is normally the diurnal minimum.
diurnal impacts almost never apply to storms of this strength
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.
Impressive. 7.0 is possible if the cloud top temperatures in the eyewall cool some more or the temperature in the eye warms.
My kids rolled on this one. Cute! LOL
indeed......
Always.
You can watch them on Google Earth. You can also watch the GRIP Global Hawk and DC-8 which are also flying in the same area on RTMM Classic on Google Earth.
Viewing: 2451 - 2501
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