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By: wxchaser97 , 11:00 AM GMT on November 01, 2013
Tropical Depression 18-E
A low pressure system has organized into tropical depression 18-E southwest of Mananzillo, Mexico. Deep convection has been increasing in organization around the center for a little while now. About 24hrs ago there was very little organized convection directly over the center, but 18-E has been able to organize in a semi-favorable environment. The surface low also has gotten better organized than it was yesterday, A recent ASCAT passed showed a closed circulation, albeit still somewhat broad, and a couple 30kt wind barbs. That, along with satellite derived intensities (TAFB at T2.0 and SAB at T1.5), has prompted the NHC to initiate advisories on the tropical depression. Upper-level outflow is pronounced on the western side of 18-E, but not so much on the eastern side. The low-level and mid-level circulations of 18-E are also tilted slightly in a westerly direction, indicating the presence of some easterly to east southeasterly shear. The current advisory info and satellite image can be found below.
2:00 AM PDT Fri Nov 1
Location: 16.4°N 108.0°W
Moving: N at 7 mph
Min pressure: 1007 mb
Max sustained: 35 mph
Forecast for TD 18-E
Tropical Depression 18-E is poised to become the EPAC's next tropical storm. The EPAC has seen a high amount of tropical cyclones this season, which is unusual given there is no El Nino. The environment that 18_E is in will be mostly favorable for further strengthening for the next 2-3 days. Wind shear is currently between 5-15kts per SHIPS analysis and UW-CIMSS shear maps. While this won't inhibit strengthening, it shouldn't allow any rapid deepening for the system. The low to moderate shear should continue for the next 3 days before sharply increasing in response to a trough moving in. SST's are over 28.5C, but will be slowly decreasing over the next couple days. The low and mid-levels look to be moist enough to allow for the continue development of deep convection for a couple of days as well. Going based off of the factors above, 18-E should be able to strengthen into a weak tropical storm before conditions become unfavorable and before it makes landfall. Global and intensity aren't very enthusiastic on the strength of 18-E. At best, they only show a weak tropical storm. Given the atmosphere isn't the most ideal for strengthening, and the model support, this seems like a likely solution. My intensity forecast is close to the NHC's.
Tropical depression 18-E is currently moving to the north at 7mph per the NHC advisory. The center looks to be located at about 16.6N and 108.0W based off of satellite loops and that ASCAT pass mentioned earlier. A mid-level ridge to the northeast of the system should turn 18-E to the WNW over the next 24hrs. While this change in direction is occurring, a mid-level trough will be dropping down from the north-northwest. In about 36hrs, 18-E should begin to turn to the north, and then northeast, in response to that trough. Global and dynamical models are in fairly good agreement with the track of 18-E. Most show the turn to the WNW followed by a N, then NE, turn in 36-48hrs. They show 18-E making landfall in about 4 days. Given the steering pattern that will be in place, there is little reason to diverge from the model consensus. My forecast track is a blend of the GFS, ECMWF, and dynamical model consensus. TD 18-E should make landfall in 84-96hrs, bringing locally heavy rain, flooding, and blustery winds to parts of Mexico. Mid-level moisture associated with 18-E could enhance more rainfall in the southern US, further helping the drought situation.
INIT 01/1100Z 30 KT 35 MPH
12H 02/0000Z 35 KT 40 MPH
24H 02/1200Z 35 KT 40 MPH
36H 03/0000Z 40 KT 45 MPH
48H 03/1200Z 40 KT 45 MPH
72H 04/1200Z 35 KT 40 MPH
96H 05/1200Z 30 KT 35 MPH...INLAND
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