803
WTPZ42 KNHC 270231
TCDEP2

Tropical Storm Vance Discussion Number  23
NWS National Hurricane Center Miami FL       EP222026
800 PM MST Mon Oct 26 2026

The structure of Vance has degraded significantly over the last
several hours as the center of the cyclone has become separated from
the convection as seen on visible satellite imagery. Based on a
combination of the subjective and objective intensity estimates, the
initial intensity has been lowered to 45 kt.

Vance has continued to move slowly to the west, 275/4 kt. The
tropical storm is expected to make a turn to west-northwest or
northwest over the next 24 h due to a weak mid-level ridge to the
north of the system. By Wednesday, a broad mid-level trough near the
Baja California Peninsula should force Vance to turn more to the
north. The current NHC track forecast remains in good agreement with
the most recent GDMI and HCCA models. There is still some model
spread in the latter portion of the track forecast, however the
current track still favors a more slower storm motion overall.

Strong westerly to southwesterly wind shear is expected to persist
and increase through the forecast period. However, given the
presence of warm water and sufficient atmospheric moisture, the
cyclone is currently forecast to weaken only gradually over the next
several days. The intensity forecast remains on the upper end of the
guidance and brings Vance to a post-tropical cyclone around 72
hours, as the convection will likely be sheared off by the
aforementioned trough by that time. It should be noted that it is
possible the system could degenerate into a remnant low sooner than
currently forecast, however, GFS and ECMWF simulated satellite
guidance indicates that intermittent convective bursts could still
occur near the center during the next few days.

Key Messages:

1. 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 southern Sinaloa,
southwest Durango, and coastal sections of Nayarit and Jalisco,
especially in areas along steep terrain.

2. Interests in southwest and west-central Mexico should
continue to monitor Vance`s progress.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 15.5N 106.3W   45 KT  50 MPH
 12H  27/1200Z 15.9N 107.1W   45 KT  50 MPH
 24H  28/0000Z 17.2N 107.9W   40 KT  45 MPH
 36H  28/1200Z 18.8N 108.3W   40 KT  45 MPH
 48H  29/0000Z 20.5N 108.3W   40 KT  45 MPH
 60H  29/1200Z 22.0N 108.1W   35 KT  40 MPH
 72H  30/0000Z 23.5N 107.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  31/0000Z...DISSIPATED

$$
Forecaster Katz/Cangialosi