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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I'm assuming you expect they will? Sorry, I haven't had a chance to go over to your update yet.
9(10)
4
3
LOL!!
Nah! This is even better....
I may be forced to take a Siesta, shortly.
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 12 SEP 2010 Time : 171500 UTC
Lat : 17:39:53 N Lon : 45:56:42 W
CI# /Pressure/ Vmax
6.2 / 944.8mb/119.8kt
Final T# Adj T# Raw T#
6.2 6.5 6.5
Let's not get carried away.. Yes, the 12z CMC has shifted significantly to the left, but it is one run. We need to see how these troughs evolve or devolve as it were.
I was thinking more along the lines of Bermuda getting wailed, but I could be wrong. Lord knows I'm no expert. ;)
Yes and yes Igor does resemble one of them though it probably has too much banding.
They look like donuts. are supercanes and can become annular and then go back to being just hurricanes. Wiki has a good explanation and here's a pdf of one. a-canes
@802.
Whispers...Wow. omg. Wow. wow.
Storm likes to tease us in order to make us work harder at learning. He's a good teacher.
i have to agree with you but its getting very frighting
--SSTs can't be below 25.4.C or higher than 28.5.C;
--Winds can't be below 85 knots or higher than 125 knots;
--Deep-layer (850-200 mb) wind shear can't be greater than 23.9 knots;
--Generalized wind shear can't be greater than 30.7 knots;
--The 200 mb zonal wind can't be less than -11 or greater than 17.2 knots;
--The radius of the coldest (brightest) cloud tops can't be less than 50 km;
--The REFC (Relative Eddy angular momentum Flux Convergence) can't be under -4.4 or greater than 8.4.
Not sure where Igor stands on all those, but I suspect he's pretty darn close...
Possibly a strong cat. 4 by 5pm.
Why is everyone having such a hard time with the name of this storm? It's IGOR! LOL!
Date : 12 SEP 2010 Time : 171500 UTC
Lat : 17:39:53 N Lon : 45:56:42 W
CI# /Pressure/ Vmax
6.2 / 944.8mb/119.8kt
Final T# Adj T# Raw T#
6.2 6.5 6.5
No Zero Nada.
Been like that all day!
Since it appears that Igor is obtaining Cat 4 and still could get stronger, how much effect would "Pumping the Ridge" have on its movement. Expecially if and when he would fell the effects of any troughs?
It's Igor, IGOR!! Lol.
it all depends on what model the NHC is leaning to. The track right now has a lot of GFS bias IMO
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 160
MILES...260 KM.
It's not that big. That'll help him achieve any greater intensity.
The pressure's a little bit high for a usual Cat 4, but it's not that uncommon.
119.8KTS~138 MPH
So at 12:15PM CDT we have a CAT 4 w/140MPH winds and a central pressure of 945MB!! AMAZING :O)!!
losin' the bubble?
Alex did not have room to run in the bay of Campeche. His winds would have matched that pressure if he'd had one more night over water.
They typically lean with the GFS ensembles.. I say typically because there are times they go the other direction.
THE OFFICIAL FORECAST IS
BASED ON PRIMARILY ON THE TVCN MULTI-MODEL CONSENSUS BUT IS
ADJUSTED SLIGHTLY TO THE LEFT OF THE PREVIOUS ADVISORY BEYOND DAY 3
AND CLOSER TO THE UKMET...ECMWF...AND THE ECMWF ENSEMBLE MEAN.
96 hour....
Viewing: 851 - 901
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