Issued at 900 AM CST Fri Sep 12 2025
000 WTPZ43 KNHC 121444 TCDEP3 Tropical Storm Mario Discussion Number 4 NWS National Hurricane Center Miami FL EP132025 900 AM CST Fri Sep 12 2025 37-GHz AMSR2 data from 0823 UTC did an excellent job showing the well-defined center of the small tropical cyclone about 20 n mi off the coast of Guerrero, Mexico. As noted in the previous forecast, an ASCAT pass from overnight showed maximum winds just over 30 kt. The convective organization has been increasing since that time, and the depression has powered up to Tropical Storm Mario with maximum winds estimated at 35 kt. This is supported by a T2.5/35 kt from TAFB and 35-40 kt objective estimates from ADT, AiDT, and SATCON. Model guidance is having a challenging time simulating Mario's future due to the storm's small size and proximity to Mexico's coastal topography. Some models, including the ECWMF and many of the Google DeepMind ensemble members, show the system moving inland and dissipating today. Assuming Mario stays offshore, it is likely to contend with moderate shear out of the north or northeast for the next 36 hours while moving over very warm water temperatures around 30 degrees Celsius. Shear is expected to be low beyond 36 hours, and some strengthening is therefore shown in the NHC intensity forecast. Some of the hurricane models continue to show Mario reaching hurricane strength, but given the large degree of uncertainty, the NHC forecast leans much closer to the IVCN consensus at this time. Mario is expected to reach colder waters by day 5, and transition to a post-tropical cyclone is shown at that time. Mario has been moving faster toward the west-northwest (295/12 kt), moving roughly parallel to the coast of Mexico. A mid-level ridge extending across northern Mexico westward over the Pacific waters is expected to keep Mario on a west-northwestward trajectory, but at a slower speed, for at least the next 4 days. The models that maintain Mario's identity agree on this scenario, and no significant changes were made to the NHC track forecast. Given Mario's very close proximity to the coast of Mexico, the government of Mexico has issued a Tropical Storm Watch for a small segment of the coast from Lazaro Cardenas to Punta San Telmo. Key Messages: 1. Heavy rainfall associated with Tropical Storm Mario will impact southern Mexico through Sunday, which could result in flash flooding, particularly in areas of higher terrain. 2. Tropical storm conditions are possible along portions of the coast of Michoacan today while Mario moves roughly parallel to the southwestern coast of Mexico. Gusty winds are possible elsewhere along the coasts of western Guerrero, Michoacan, and Colima through tonight. Interests in these areas should continue to monitor the progress of Mario. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 17.2N 101.9W 35 KT 40 MPH 12H 13/0000Z 17.7N 103.7W 35 KT 40 MPH 24H 13/1200Z 18.2N 105.5W 35 KT 40 MPH 36H 14/0000Z 18.7N 107.1W 40 KT 45 MPH 48H 14/1200Z 19.1N 108.5W 45 KT 50 MPH 60H 15/0000Z 19.5N 110.0W 50 KT 60 MPH 72H 15/1200Z 20.1N 111.4W 55 KT 65 MPH 96H 16/1200Z 21.7N 114.2W 40 KT 45 MPH 120H 17/1200Z 23.5N 117.2W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Berg
