Issued at 800 AM PDT Tue Sep 16 2025
773 WTPZ43 KNHC 161450 TCDEP3 Tropical Storm Mario Discussion Number 16 NWS National Hurricane Center Miami FL EP132025 Issued by the NWS Weather Prediction Center College Park MD 800 AM PDT Tue Sep 16 2025 Convection associated with Mario continues to diminish this morning as the system moves into cooler waters and encounters increasing southwesterly shear. Satellite intensity estimates from TAFB and SAB are decreasing, and thus the initial intensity was lowered to 40 kt this advisory. The initial location of Mario remains a bit uncertain, although a recent microwave pass from shortly after 09Z indicated the system is likely farther southwest than anticipated. As Mario continues to weaken and lose vertical structure, the expectation is that the shallow low-level circulation will slow down and feel less of an impact from the deep-layer southerly flow. This should result in an increasingly sheared system, with the low-level circulation staying farther west and the mid-level remnants going northward. Given this, the latest track forecast is slightly west of the previous forecast, generally remaining on the western side of the track guidance. Mario will continue to weaken as it moves over cooler waters and increasing shear. As the low-level and mid-level circulation decouple, the system will lose its organized convection and should become a post-tropical remnant low as soon as tonight. Thereafter, the low should dissipate into a trough by 48-60 h. While Mario is forecast to dissipate as a tropical cyclone well to the south of California, its remnant moisture will spread farther north, affecting portions of the southwestern United States by mid to late week. Locally heavy rainfall and some instances of flash flooding will be possible by Thursday. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 22.7N 117.2W 40 KT 45 MPH 12H 17/0000Z 23.7N 118.2W 30 KT 35 MPH 24H 17/1200Z 24.9N 119.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 18/0000Z 25.8N 120.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 18/1200Z 26.0N 120.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 19/0000Z...DISSIPATED $$ Forecaster Chenard/Blake
