Issued at 300 AM CST Thu Oct 08 2026
000 WTPZ45 KNHC 080855 TCDEP5 Tropical Storm Simon Discussion Number 4 NWS National Hurricane Center Miami FL EP202026 300 AM CST Thu Oct 08 2026 This evening's conventional satellite imagery and a recent ASCAT overpass and a 0323 UTC MetOp-SG1 MI indicate that Simon is developing a compact inner core structure. There are also curved bands with -73C to -82C cold cloud tops forming in the west and northeast portions of the cyclone. The TAFB subjective satellite intensity estimate is T3.0/45 kt and a blend of the UW-CIMSS objective estimates (41-47 kt) yield an initial intensity of 45 kt. The shear is low, the atmosphere is moist, and the ocean is warm with high heat content values, all contributing to a high probability of Simon quickly intensifying during the next couple of days. The upper wind pattern is also quite favorable with impressive diffluent easterly flow ventilating the western portion of the cyclone. The latest SHIPS RI Index shows a 63 percent chance of a 55 kt increase in 48 hrs, while the UW-CIMSS AI-RI indicates a similar likelihood of rapid intensification. The official forecast shows Simon becoming a major hurricane in 48 hrs with a peak intensity of 115 kt on Saturday, and this is based on the HFIP-HCCA and slightly above the Google DeepMind ensemble guidance. Simon's initial motion is estimated to be due west, or 270 degrees at 6 kt. This general motion should continue through today while being steered by high pressure north of the cyclone over central Mexico. On Friday, the system should turn west-northwestward to north-northwestward in response to a mid-tropospheric trough approaching Baja California. Toward the end of the period, Simon is expected to move northward ahead of and on the southeastern side of the aforementioned trough and approach the southwestern coast of Mexico over the weekend. The GFS and the ECMWF HiRes global models still show outlier tracks to the left of the NHC forecast but have been trending eastward, aligning more with the better-performing HCCA and Google DeepMind TC ensemble mean aids, which the official forecast leans toward. Simon's 34 kt wind radii were decreased a bit based on a 0403 UTC METOP-B ASCAT pass. Key Messages: 1. Simon is expected to strengthen into a hurricane by early Friday and approach the west-central coast of Mexico as a major hurricane on Saturday. Tropical storm conditions are possible within the tropical storm watch area early Friday. There is also risk of dangerous wind and storm surge impacts along portions of this coast over the weekend and into early next week and additional watches will likely be required for portions of southwestern Mexico. 2. Heavy rainfall associated with Simon will impact portions of southwestern Mexico later this week and into the weekend. This rainfall may produce life-threatening flooding and mudslides, especially in areas of steep terrain. 3. 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 08/0900Z 15.4N 103.1W 45 KT 50 MPH 12H 08/1800Z 15.4N 104.1W 60 KT 70 MPH 24H 09/0600Z 15.9N 105.1W 75 KT 85 MPH 36H 09/1800Z 16.6N 105.5W 95 KT 110 MPH 48H 10/0600Z 17.4N 105.6W 110 KT 125 MPH 60H 10/1800Z 18.3N 105.4W 115 KT 130 MPH 72H 11/0600Z 19.3N 105.3W 110 KT 125 MPH 96H 12/0600Z 21.8N 105.7W 80 KT 90 MPH 120H 13/0600Z 24.3N 106.1W 55 KT 65 MPH...INLAND $$ Forecaster Roberts
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