Tropical Cyclone Discussion
656 WTPZ42 KNHC 252035 TCDEP2 Tropical Storm Vance Discussion Number 18 NWS National Hurricane Center Miami FL EP222026 300 PM CST Sun Oct 25 2026 Vertical wind shear and relatively dry mid-level air are negatively impacting Vance's structure today. An earlier RCM-2 microwave pass indicated that the center was slightly elongated, with an opening on the southeastern side. Deep convection has been intermittent over the past 6 h or so, and has been concentrated primarily north and east of the center. However, an ASCAT-C pass indicated peak winds of 50-53 kt to the west and northwest of the center. Subjective and objective intensity estimates have continued to trend downward, ranging from 46-65 kt. The initial intensity is set at 60 kt for this advisory, based on a blend of these estimates and the available satellite data. Vance is moving at 330/06 kt, steered by a mid-level ridge centered over the south-central United States, along with a closed upper-level low moving across the southwestern U.S. The tropical storm is expected to move toward the northwest or west-northwest at a slower forward speed over the next couple of days as steering currents weaken. A turn toward the north is forecast around midweek as an amplified upper-level trough moves across the eastern Pacific. The latest NHC track forecast has been adjusted westward once again to reflect trends in the global and regional hurricane model guidance. However, the track still remains near the eastern edge of the guidance envelope, and additional westward adjustments may be needed in subsequent forecast cycles. Westerly to southwesterly wind shear and relatively dry mid-level air are expected to support gradual weakening over the next several days. By midweek, the upper-level trough is forecast to produce a significant increase in wind shear, leading to further weakening. By late this week, simulated satellite imagery from the ECMWF and GFS suggests that Vance may struggle to sustain organized deep convection. The forecast calls for Vance to become post-tropical by 96 h and degenerate into a remnant low by 120 h. Key Messages: 1. Although the threat of impacts to Mexico is trending downward as the forecast track continues to shift westward and away from the coast, uncertainty remains in both the track and intensity forecasts. Interests in southwestern Mexico should continue to monitor the progress of Vance. 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 Colima, Nayarit, and Sinaloa, along with western portions of Michoacán, Jalisco, and Durango, especially in areas along steep terrain. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 14.9N 104.2W 60 KT 70 MPH 12H 26/0600Z 15.0N 104.8W 60 KT 70 MPH 24H 26/1800Z 15.4N 105.5W 55 KT 65 MPH 36H 27/0600Z 16.0N 106.2W 50 KT 60 MPH 48H 27/1800Z 16.9N 106.6W 45 KT 50 MPH 60H 28/0600Z 17.7N 107.0W 45 KT 50 MPH 72H 28/1800Z 19.0N 107.2W 45 KT 50 MPH 96H 29/1800Z 21.0N 107.4W 40 KT 45 MPH...POST-TROPICAL 120H 30/1800Z 23.3N 107.2W 30 KT 35 MPH...POST-TROP/REMNT LOW