000
WTPZ42 KNHC 260838
TCDEP2
 
Tropical Storm Vance Discussion Number  20
NWS National Hurricane Center Miami FL       EP222026
300 AM CST Mon Oct 26 2026

Vance has not changed significantly in organization over the past 
several hours.  There are disorganized bursts of deep convection 
near and east of the estimated center, but convective banding 
features are not well defined.  Upper-level outflow is mainly over 
the northern semicircle of the system.  The advisory intensity is 
held at 55 kt for now, which is in agreement with a subjective 
Dvorak estimate from TAFB and a little higher than most of the 
objective estimates from UW-CIMSS.  

Although the center is difficult to locate, it is estimated to be 
situated near the western side of the main area of convection.  The 
storm appears to still be moving slowly northwestward, with an 
initial motion estimate of around 305/5 kt.  A slow 
west-northwestward track is likely over the next 36 hours or so due 
to a weak mid-level ridge to the north of the system.  In a couple 
of days, a broad mid-level trough near the Baja California peninsula 
should induce a turn toward the north, and the weakening cyclone 
should then move northward and approach mainland Mexico later this 
week.  The official track forecast is shifted somewhat to the west 
of the previous one, but not as far west as much of the model 
guidance.  Additional westward adjustments may be required in 
subsequent advisory packages.

Vance remains in an environment of strong westerly vertical wind 
shear and in a somewhat dry mid-level air mass.  The SHIPS guidance 
indicates that the strong shear should persist for the next few 
days.  Therefore weakening is anticipated as in the previous NHC 
forecast.  Simulated satellite imagery from the ECMWF global model 
output shows Vance losing most of its deep convection after 72 
hours.  Thus, the system is expected to become a post-tropical 
remnant low by late this week.  The official forecast is on the high 
side of the intensity model guidance suite.


Key Messages:
 
1. Although the threat to southwest Mexico is decreasing as the 
forecast track shifts westward away from the coast, interests there 
should continue to monitor Vance's progress.
 
2. Periods of heavy rainfall associated with Vance will impact 
portions of western Mexico during much of this week.  This rainfall 
may produce flooding and mudslides across Sinaloa and along western 
portions of Jalisco, Nayarit and Durango, especially in areas along 
steep terrain.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/0900Z 15.3N 105.1W   55 KT  65 MPH
 12H  26/1800Z 15.6N 105.9W   50 KT  60 MPH
 24H  27/0600Z 16.1N 106.9W   45 KT  50 MPH
 36H  27/1800Z 17.2N 107.6W   40 KT  45 MPH
 48H  28/0600Z 18.5N 108.0W   40 KT  45 MPH
 60H  28/1800Z 19.9N 108.1W   40 KT  45 MPH
 72H  29/0600Z 21.4N 108.0W   35 KT  40 MPH
 96H  30/0600Z 23.2N 107.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  31/0600Z 24.5N 108.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Pasch