Issued at 200 PM MST Sat Oct 04 2025
827 WTPZ41 KNHC 042033 TCDEP1 Tropical Storm Priscilla Discussion Number 1 NWS National Hurricane Center Miami FL EP162025 200 PM MST Sat Oct 04 2025 The satellite presentation of Invest 99E has continued to improve today, with an elongated convective band having formed through the western and northern part of the circulation. Given the system’s broad nature, its center definition had been questionable, particularly based on ASCAT data from yesterday evening. However, a recent 1645 UTC ASCAT pass showed that the center has become significantly better defined, with 35-40 kt winds occurring north and northwest of the center. Based on these data, advisories are being initiated on Tropical Storm Priscilla, with an estimated intensity of 40 kt. Priscilla is moving northwestward (315 degrees) at 8 kt. A large-scale trough is currently located over the western United States and extends southward over Baja California, leaving Priscilla in an environment of weak steering currents. In the short term, that should cause the storm to slow down and drift in a general northward direction for the next 36 hours. After that time, Priscilla is expected to settle in to a more steady northwestward track as a stronger mid-level ridge builds over northern Mexico and the deep-layer trough remains entrenched over the western United States. For most of the forecast period, the NHC track forecast leans on the eastern side of the guidance envelope, in the vicinity of the ECMWF, HCCA consensus aid, and Google DeepMind ensemble mean. Priscilla will be moving over sea surface temperatures of about 29 degrees Celsius during the next couple of days, coincident with a period of strong upper-level divergence. These conditions should support strengthening, although the system's large size could limit the rate of intensification in the short term. That said, some of the Rapid Intensification (RI) indices are greater than 50% within 36 and 48 hours, so if Priscilla can develop a tighter inner core within the larger wind field, more significant strengthening would be possible. The NHC intensity forecast calls for Priscilla to become a hurricane by Sunday night, with strengthening continuing through Tuesday. Cooler water temperatures and a less favorable atmosphere should induce weakening by Wednesday and Thursday. KEY MESSAGES: 1. Tropical storm conditions are possible along portions of the coast of southwestern Mexico within the watch area Sunday and Monday. Interests in the southern portion of Baja California Sur should also monitor the progress of Priscilla. 2. Heavy rainfall associated with Priscilla will impact coastal sections of southwestern Mexico through Monday, which could result in flash flooding, particularly in areas of higher terrain. 3. Swells generated by Priscilla are affecting portions of the coast of southwestern Mexico and will reach the coasts of west-central Mexico and the southern Baja California peninsula by Monday. These swells are likely to cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 15.5N 106.6W 40 KT 45 MPH 12H 05/0600Z 15.8N 106.8W 45 KT 50 MPH 24H 05/1800Z 16.3N 106.9W 55 KT 65 MPH 36H 06/0600Z 17.0N 107.3W 65 KT 75 MPH 48H 06/1800Z 17.8N 108.2W 75 KT 85 MPH 60H 07/0600Z 18.8N 109.4W 80 KT 90 MPH 72H 07/1800Z 19.7N 110.7W 85 KT 100 MPH 96H 08/1800Z 21.7N 113.3W 80 KT 90 MPH 120H 09/1800Z 24.1N 115.4W 60 KT 70 MPH $$ Forecaster Berg
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