Tropical Storm Vance

110 
WTPZ42 KNHC 261434
TCDEP2
 
Tropical Storm Vance Discussion Number  21
NWS National Hurricane Center Miami FL       EP222026
900 AM CST Mon Oct 26 2026
 
Vance is experiencing 15 to 20 kt of west-southwesterly vertical
wind shear.  It appears that the surface center is near the
west-southwest edge of the main convective area.  The latest TAFB
Current Intensity number remains 3.5/55 kt.  Recent objective
intensity estimates from UW-CIMSS have been running in the 45-55 kt
range.  The initial intensity is held at 55 kt for this advisory.

Vance's estimated motion is west-northwestward or 295/6 kt, aided by 
GPMI and AMSR-3 microwave passes from around 0800 UTC.  This slow 
west-northwestward track is expected to continue over the next 24 
hours or so 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 induce a turn toward the north.  The NHC 
track forecast has again been shifted to the west of the previous 
one, but not as far west as the Google DeepMind Ensemble Mean.  The 
official forecast is in good agreement with the latest HFIP 
Corrected Consensus Approach (HCCA).

Although Vance remains in a favorable thermodynamic environment with 
warm water and enough atmospheric moisture, the cyclone is 
experiencing moderate to strong west-southwesterly wind shear.  The 
wind shear is forecast to increase a bit more (to near 25 kt) over 
the next 12 to 24 hours, and this should be enough to cause steady 
weakening over the next day or so.  On Wednesday, as Vance turns 
northward and gets closer to the broad trough over Baja California 
and the subtropical jet, the west-southwesterly vertical wind shear 
increases to over 35 kt, and is forecast to increase further on 
Thursday.  Surprisingly, most of the models hold onto this system as 
a tropical storm for a couple more days.  The NHC forecast is 
slightly lower than the previous forecast, and lies in the middle of 
the guidance envelope through 48 hours, near the HCCA model.  From 
60 hours onward, the NHC intensity forecast is near the lower end of 
the model guidance suite, near the average of the GDMI and HCCA 
models.  It is likely that Vance's convection will be sheared off by 
72 hours, and the new forecast has moved up post-tropical timing to 
this period.  Nearly all of the models show the circulation 
dissipating by day 5, so the NHC forecast shows dissipation by this 
time, just before it reaches the coast of Mexico.

 
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, Jalisco, Colima 
and Michoacan, especially in areas along steep terrain.

2. Although the wind 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.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/1500Z 15.4N 105.7W   55 KT  65 MPH
 12H  27/0000Z 15.7N 106.6W   45 KT  50 MPH
 24H  27/1200Z 16.4N 107.6W   40 KT  45 MPH
 36H  28/0000Z 17.6N 108.2W   40 KT  45 MPH
 48H  28/1200Z 19.2N 108.4W   40 KT  45 MPH
 60H  29/0000Z 20.7N 108.4W   35 KT  40 MPH
 72H  29/1200Z 22.0N 108.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  30/1200Z 24.1N 108.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  31/1200Z...DISSIPATED
 
$$
Forecaster Hagen