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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If you don't see the wobble to wsw, you're not looking very hard!
Better keep that one handy
Morning BT. I guess we'll see if 92L is going to take advantage of that hot water.
Earl?
LOL I'm tired exuse my reference to a dead and gone storm.
105mph, just like I guessed...woohoo. i got it right. the pressure is lower than I guessed.. so an 18 mb drop in 6 hrs.. impressive
In the last 10 years of watching models I have never seen one try to break anything near a 1025 ridge. Yes that cannot happen although I have seen hurricanes put a weakness in ridges up to 1020 when trapped that they then went through. But in the ECMWF model that was posted and all the current models the trough is creating a weakness with the Igor going through the 1012MB isobar which it will easily do.
The forecast track is sound but the timing and intensity of the trof and the ridge is still to be determined.
Since there is no Extra tropical low north east of the ridge to reinforce it( although igors outflow might help it out) and the trof is getting a little extra energy from absorbing the small low in the mid-atlantic as well as the fact that North Atlantic/polar lows start to tend to become stronger this time of year I think the GFS model is more accurate and we will soon re-curve start tomorrow with Igor being no threat to land other than Bermuda
Earl 5-minute interval:
Earl SRSO loops (both greater than 25 MB):
http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2010/08/100824_g15_vis_srso_anim.gif
http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2010/08/100824_g15_vis_srso_2_anim.gif
Contrast that to Alex's 947 with 105 mph winds.
it sure is i think this could pull an Isabel,Fran track or a Frances track because the ship models shows a slight bend back west at the end of the forecast period
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....
Very impressive eyewall.
92L looks like it is wrapping convection around a coc at approximately 72.2W/16N.
I love that Alex loop. Alex was a good storm to track, going through a pre-landfall RI and all. Too bad it did all of that bad stuff to Mexico.
I was noticing that this morning when I woke up, and I see the models after taking Igor on a NW path bend it back to the WNW. Only the GFS for now insists on the re-curvature. Also the path that 92L takes the more further west it goes may dictate the path that Igor takes if the trough is not strong enough to pull it out to sea.
Earl had a left of track bias for days. This sure looks similar. Can't trust the wobbles! They get lots of people excited tho! If ya bet against the TPC/NHC on a regular basis, you'll lose a bunch of money!
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
yes
It def looks like he may cut it close
That could be a candidate for the A word down the line.
Not unless it has learned teleportation.
TD12 IS OFF THE COAST OF AFRICA
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