Tropical Cyclone Discussion
126 WTPZ45 KNHC 091447 TCDEP5 Hurricane Simon Discussion Number 9 NWS National Hurricane Center Miami FL EP202026 900 AM CST Fri Oct 09 2026 The intensity of Simon has been hard to diagnose this morning. The most recent TAFB Dvorak fix still supported an intensity of 80 kt at 1200 UTC, while all of the objective techniques from UW-CIMSS are lower. Since that time, a warm spot near the center of Simon's small CDO has recently appeared, which appears to be the early development of an eye. Based on the continued improvement in Simon's satellite appearance, the initial intensity has been increased to 85 kt for the advisory. Over the next 24 hours, continued rapid intensification is expected. The RI probabilistic guidance (both SHIPS and DTOPS) actually decreased this cycle, but the hurricane is located in a low-shear, high-moisture, and high-SST environment that is conducive for explosive deepening. Furthermore, recent microwave imagery, such as an AMSR3 pass just after 08Z suggests the hurricane has a small inner-core, which makes rapid changes in intensity more likely. Therefore, the NHC forecast is in line with the previous one, above most of the guidance and shows Simon becoming a major hurricane later today. Simon's forecast beyond that is extremely difficult, and this is a case where it is important to not focus on the details of NHC's deterministic forecast. Simon will turn northward this weekend, steered between a deep trough to its northwest and a ridge to the east. This track will take the center of Simon very near or over the Mexican states of Colima and Jalisco. If the center of Simon moves over land, it will quickly weaken and could even dissipate, drastically lessening the risk of hurricane-force-winds farther north in Mexico. However, if the core of Simon remains offshore, it will likely continue northward as a hurricane. A majority of the guidance this morning shows Simon remaining just offshore, however most of these models have historically had a west bias in this region. Likewise, ensemble means like GDM or even HCCA can be misleading when some members move inland and dissipate. This results in the mean being computed solely from the surviving, and in this case farther west, members. The NHC forecast therefore remains within, but on the east side of the guidance envelope, and is best characterized as a hedge between the aforementioned possibilities. Key Messages: 1. Simon is expected to approach the west-central coast of Mexico as a major hurricane on Saturday. 2. Catastrophic wind and life-threatening storm surge impacts are likely 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 today. 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 09/1500Z 16.0N 104.7W 85 KT 100 MPH 12H 10/0000Z 16.5N 104.8W 105 KT 120 MPH 24H 10/1200Z 17.2N 104.9W 125 KT 145 MPH 36H 11/0000Z 18.2N 105.0W 125 KT 145 MPH 48H 11/1200Z 19.4N 105.2W 115 KT 130 MPH 60H 12/0000Z 20.7N 105.4W 95 KT 110 MPH...INLAND 72H 12/1200Z 21.9N 105.6W 75 KT 85 MPH...OVER WATER 96H 13/1200Z 23.6N 106.2W 55 KT 65 MPH...INLAND 120H 14/1200Z 24.9N 106.9W 30 KT 35 MPH...POST-TROP/INLAND