Tropical Storm Vance

000
WTPZ42 KNHC 291432
TCDEP2
 
Tropical Storm Vance Discussion Number  33
NWS National Hurricane Center Miami FL       EP222026
800 AM MST Thu Oct 29 2026
 
Deep convection near the center yesterday evening produced 
tropical-storm-force winds in Vance's northern and eastern 
semicircles.  Strong (50 kt) west-southwesterly vertical wind shear 
has been pushing the deep convection farther and farther away from 
the center over the past 9 to 12 hours, and now the convection is 
located more than 90 n mi east and northeast of the center.  Recent 
surface observations from Islas Marias are 20 kt gusting to 30 kt 
while located underneath some of the deepest convection for the past 
few hours, so the winds are likely decreasing, but it is still 
possible that a small area of winds to tropical-storm-force exists 
in that convection, so Vance will be held at 35 kt for this 
advisory.  Scatterometer passes expected within the next couple of 
hours should give us a better assessment of Vance's strength.
 
The UW-CIMSS shear analysis and the latest SHIPS guidance are both 
analyzing about 50 kt of west-southwesterly vertical wind shear 
currently impacting Vance.  The shear is forecast to increase to 
around 55 kt over the next 6 h or so.  Vance is also located within 
a drier environment than it was yesterday, with mid-level relative 
humidity values in the 40 to 50 percent range. Therefore, deep 
convection, which is currently located well east of the center and 
moving farther away, is unlikely to return, and the GFS and ECMWF 
simulated satellite products do not forecast any new convection to 
form near the center.  Therefore, the timing of post-tropical 
transition has been moved up to hour 12 in the official forecast. 
Most of the models then show the remnant low dissipating in about 18 
to 24 hours over the southern Gulf of California.  Although gradual 
weakening is forecast until dissipation, gusts to 
tropical-storm-force are still likely today within the deep 
convection well east of the center.
 
Vance has been moving northward, or 350/7 kt.  A generally northward 
motion at about the same speed is expected until Vance degenerates 
into a trough of low pressure over the southern Gulf of California 
in about 18 to 24 hours.  The new NHC forecast is nudged a bit to 
the left of the previous one and is near the latest HCCA and GDMI. 
It should be emphasized that the main threat with Vance is the very 
heavy rainfall and high rain rates near the areas of very deep 
convection near the Islas Marias and west-central Mexico.
 
 
Key Messages:
 
1. Periods of heavy rainfall associated with Vance will impact
portions of western Mexico during the next day or two. This rainfall
may produce flooding and mudslides across central and southern
Sinaloa, far southwestern Durango, and far northwestern Nayarit,
especially in areas along steep terrain.
 
2. Moisture carried northeastward from Vance will produce heavy rain
across portions of the U.S. Southern Plains and New Mexico today
into Friday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 21.6N 108.8W   35 KT  40 MPH
 12H  30/0000Z 22.9N 108.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 24H  30/1200Z...DISSIPATED
 
$$
Forecaster Hagen