Tropical weather analysis - November 19, 2011
Tropical Depression Thirteen-E
In a rare circumstance, the Eastern Pacific managed to churn out a tropical depression today. TD13-E is the latest forming tropical cyclone in the Eastern Pacific since Hurricane Sergio in 2006 formed on November 13. Additionally, should it become a tropical storm, it will be the latest-forming tropical storm in the historical database since Hurricane Winnie of 1983. As of the latest NHC advisory, the following was posted:
Wind: 35 mph, with higher gusts
Location: 10.3°N 102.1°W
Movement: W at 12 mph
Pressure: 1006 mb
Category: Tropical depression (Saffir-Simpson Hurricane Scale)
The depression has made a bit of a comeback this evening, after a brief convective lull during the diurnal minimum. In addition to the mass of convection covering the low-level center, a loose band of thunderstorms is found downstream of that.
Figure 1. Latest infrared satellite image of Tropical Depression Thirteen-E, courtesy of NOAA's Satellite Services Division (SSD).
Environmental conditions appear favorable for intensification, with light shear, high moisture, and warm SSTs. The depression should become a tropical storm tomorrow, and a hurricane in about three to four days. One possible inhibiting factor in later periods could be an area of dry air from 110W westward. After about 96 hours, the cyclone will encounter the 26C isotherm, and an increase in westerly shear. This should then bring about weakening, possibly rapid at the end of the period.
The depression is expected to turn west-northwest soon as an upper trough to the west weakens the subtropical ridge to the north. After about a day or so, this trough lifts out and the ridge rebounds, which then forces the depression westward again. By 72-96 hours, a secondary trough is forecast to weaken the ridge again, causing the tropical cyclone to turn more poleward. With the exception of the GFDL and HWRF, which appear to be eastern outliers, the track guidance is in excellent agreement with this.