Tropical Cyclone Discussion
863 WTPZ45 KNHC 081437 TCDEP5 Tropical Storm Simon Discussion Number 5 NWS National Hurricane Center Miami FL EP202026 900 AM CST Thu Oct 08 2026 Simon continues to steadily become better organized. Satellite and microwave images indicate that the storm has a compact inner core and much larger rainbands surrounding it. The outer bands on the northeast side of the circulation are moving across coastal areas of southwestern Mexico, likely bringing heavy rains and gusty winds there. The latest satellite intensity estimates range from 45 to 55 kt, and the initial intensity is set at the high end of the estimates at 55 kt. The tropical storm is moving slowly westward at about 5 kt, steered by a weak mid-level ridge to its north. A continued slow west to west-northwest motion is expected through tonight as that ridge remains in place. However, a sharp turn to the north is forecast on Friday when the ridge weakens and shifts eastward, in response to an approaching mid- to upper-level trough. Although the models generally agree on the large-scale steering pattern evolution, there are very important differences in where and when the system makes that turn. Most of the AI models, including GFSAI, ECAI, and GDMI show the turn occurring well east of the physics-based models. Since the physics-based models have often had a westward bias in this region, the NHC track forecast has been nudged eastward to be in better agreement with the latest AI guidance. This forecast brings the core of the system inland over southwestern and west-central Mexico Saturday night or early Sunday. Environmental conditions are expected to be quite conducive for strengthening, including low wind shear, very warm waters, and high moisture. Based on these favorable conditions and the compact inner core structure, rapid intensification is forecast, and Simon is expected to become a hurricane later today and a very dangerous category 4 hurricane before it reaches the coast of Mexico. This forecast lies near the high end of the guidance, in best agreement with the HCCA model. Based on the latest forecast, the government of Mexico has issued a Hurricane Watch for portions of west-central Mexico. Key Messages: 1. Simon is expected to strengthen to a hurricane later today and approach the west-central coast of Mexico as a major hurricane on Saturday and Saturday night. 2. The risk of life-threatening wind and storm surge impacts is increasing for portions of the west-central coast of Mexico, and a Hurricane Watch is now in effect from Manzanillo to Punta Mita. Preparations to protect life and property should be completed by Saturday. 3. Heavy rainfall associated with Simon will impact portions of southwestern Mexico through this weekend. This rainfall may produce life-threatening flooding and mudslides, especially in areas of steep terrain. 4. Swells will affect portions of the southwestern and west-central coast of Mexico through the weekend. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 15.4N 103.3W 55 KT 65 MPH 12H 09/0000Z 15.5N 104.1W 70 KT 80 MPH 24H 09/1200Z 16.1N 104.9W 85 KT 100 MPH 36H 10/0000Z 16.9N 105.1W 100 KT 115 MPH 48H 10/1200Z 17.6N 105.1W 115 KT 130 MPH 60H 11/0000Z 18.7N 105.1W 115 KT 130 MPH 72H 11/1200Z 19.7N 105.1W 115 KT 130 MPH...INLAND 96H 12/1200Z 22.2N 105.6W 65 KT 75 MPH...INLAND 120H 13/1200Z 25.1N 106.0W 30 KT 35 MPH...POST-TROP/INLAND