Tropical Cyclone Discussion
062 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