Tropical Cyclone Discussion
963 WTPZ42 KNHC 242040 TCDEP2 Hurricane Vance Discussion Number 14 NWS National Hurricane Center Miami FL EP222026 300 PM CST Sat Oct 24 2026 Vance has become significantly less organized since the last advisory due to a combination of cold water near the center and increasing southwesterly shear. Microwave data indicates that the eyewall has broken open, with the remaining convection limited to north of the center. In addition, visible imagery shows the low-level center to be near or a little south of the southern edge of the convective mass. The various satellite intensity estimates have dropped, and based on them the initial intensity is lowered to 80 kt. This could be quite generous, as the current structure does not look much like a hurricane. The intensity forecast is still problematic, but perhaps a little less so than earlier. Vance is likely to weaken during the next 12-18 h as it crosses a pool of colder water with temperatures near 27C that has been upwelled by several previous tropical cyclones, while at the same time it experiences at least moderate southwesterly shear. Beyond that time, the center is expected to move over sea surface temperatures near 29C closer to the coast of Mexico. This could allow intensification if the shear is light enough and the storm structure is still good enough to allow it. The GFS and ECMWF continue show a period of reduced, but still marginal, shear that could allow some intensification, and based on this and trends in the guidance slight re-intensification is shown at 48 h. By the end of the forecast period, increasing shear is likely to cause Vance to steadily weaken. It is still possible that Vance could weaken more than forecast before reaching warmer water and that the shear may be too strong to allow re-intensification after 36 h. The new intensity forecast has major downward adjustments from the previous forecast. The initial motion remains north-northwestward or 340/5 kt. Vance is being steered by a weak low- to mid-level ridge over eastern Mexico, and it is approaching a large mid-latitude trough over the western United States and northwestern Mexico. While neither of these features will change much during the next few days, Vance is likely to move into an area of lighter steering currents near the base of the trough and slow its forward motion during the next 24 or so. The track forecast beyond that time is dependent on the cyclone's strength and vertical structure. A weaker system that shears apart like shown in the UKMET and Canadian is likely to move west-northwestward to northwestward before resuming a more northerly motion, while a stronger and vertically deeper system is likely to continue slowly northward or north-northwestward. The track guidance envelope has shifted westward since the previous advisory, and the new forecast track has been nudged westward as well. Additional westward adjustments to the track may be necessary if Vance continues to lose organization. Key Messages: 1. Due to the uncertainties in both the track and intensity forecasts, it is too early to say what wind and storm surge impacts Vance may cause along the coast of Mexico. Interests in southwestern Mexico should continue to monitor the progress of the hurricane. 2. Heavy rainfall associated with slow-moving Hurricane Vance will impact the western coast of Mexico from Michoacán to Jalisco during much of next week. This rainfall may produce life-threatening flooding and mudslides across Colima and western portions of Michoacán and Jalisco, especially in areas along steep terrain. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 13.3N 103.3W 80 KT 90 MPH 12H 25/0600Z 14.0N 103.6W 75 KT 85 MPH 24H 25/1800Z 14.9N 104.0W 70 KT 80 MPH 36H 26/0600Z 15.6N 104.4W 70 KT 80 MPH 48H 26/1800Z 16.0N 104.6W 75 KT 85 MPH 60H 27/0600Z 16.4N 104.8W 70 KT 80 MPH 72H 27/1800Z 17.0N 104.9W 65 KT 75 MPH 96H 28/1800Z 18.1N 105.2W 50 KT 60 MPH 120H 29/1800Z 19.3N 105.6W 40 KT 45 MPH