Tropical Cyclone Discussion
586 WTPZ45 KNHC 090321 CCA TCDEP5 Hurricane Simon Discussion Number 7...Corrected NWS National Hurricane Center Miami FL EP202026 900 PM CST Thu Oct 08 2026 Corrected malformed non-unicode character in third paragraph. Simon has become a hurricane this evening. The satellite presentation consists of a developing small, intense, central dense overcast with -82C cold cloud tops, and a primary curved band wrapping into the center from the northwest part of the cyclone. The TAFB Dvorak satellite intensity estimate is 65 kt, as well as the initial intensity for this advisory. Simon's wind radii were adjusted based on a 1920 UTC OSCAT-3 overpass. All conducive ocean heat content, dynamic, and thermodynamic environmental contributions indicate that Simon should quickly intensify during the next 24-36 hrs. Subsequently, the SHIPS RI index shows a near 70 percent that the cyclone intensity will increase by 30 kt in 24 hrs. This seems quite reasonable given that Simon's inner core is rather small, indicative of a recent AMSR3 MI pass. Accordingly, the official intensity forecast will continue to predict an RI event on Friday, with Simon becoming a category 4 hurricane while heading toward the coast of west-central Mexico. The NHC intensity forecast is similar to the previous one, is close to the HFIP-HCCA, and now shows a peak intensity of 120 kt on Saturday morning. Simon's initial motion is estimated to be west-northwestward, or 295/5 kt. A turn to the northwest is expected by early Friday. A northward motion is forecast by early Saturday while high pressure over central Mexico weakens and shifts eastward, in response to an amplifying mid-tropospheric trough approaching Baja California. The HiRes global models that have been to the left of the forecast track outliers have trended eastward during the past 24 hours, and now align more with the skilled HCCA and GDMI aids. Therefore, confidence in the forecast track is increasing. The official forecast is slightly to the left of the previous advisory and a little slower to conform to the HCCA model, which includes the Google DeepMind TC ensemble mean. Key Messages: 1. Simon is expected to approach the west-central coast of Mexico as a major hurricane on Saturday. 2. Life-threatening wind and storm surge impacts are expected along a portion of the west-central coast of Mexico, and a Hurricane Warning is in effect from Punta San Telmo to Punta Mita. Preparations to protect life and property should be completed by late Friday. 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 09/0300Z 15.6N 104.6W 65 KT 75 MPH 12H 09/1200Z 16.1N 105.0W 85 KT 100 MPH 24H 10/0000Z 16.9N 105.2W 100 KT 115 MPH 36H 10/1200Z 17.8N 105.3W 120 KT 140 MPH 48H 11/0000Z 19.0N 105.3W 110 KT 125 MPH 60H 11/1200Z 20.4N 105.3W 75 KT 85 MPH...INLAND 72H 12/0000Z 21.6N 105.3W 35 KT 40 MPH...INLAND 96H 13/0000Z 23.3N 105.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 14/0000Z...DISSIPATED