Issued at 800 AM PDT Fri Oct 03 2025
000 WTPZ45 KNHC 031433 TCDEP5 Tropical Storm Octave Discussion Number 14 NWS National Hurricane Center Miami FL EP152025 800 AM PDT Fri Oct 03 2025 Octave has changed little during the past several hours. The system still appears to be sheared, and satellite intensity estimates are similar to six hours ago, so the intensity is held at 45 kt for this advisory. The outlook for Octave is relatively high confidence for the next day or so. Octave should continue moving west-northwestward near 7 kt, steered by a small mid-level ridge centered between Octave and the Baja California Peninsula. During that time, it should also remain somewhat sheared with its intensity only fluctuating slightly up or down over that period. Confidence in the NHC forecast is high through Saturday. However, by Saturday evening, the uncertainty in the forecast grows substantially. First, the aforementioned ridge is expected to weaken, resulting in very weak steering flow for the following couple of days. A trough over the far northern east Pacific will probably cause Octave to turn and drift eastward during that time. After that, another larger disturbance to Octave's east will likely also influence Octave's track, potentially causing it to move faster toward the east by the middle of next week. With steering currents weak, only small changes in the environment could have a large impact on Octave's track. The spread in the track guidance grows substantially beyond 48 h, so confidence in the forecast is much lower at that point. The intensity is likewise uncertain beyond 24 to 36 h. The shear affecting Octave is expected to lessen, and the tropical storm should be in an environment otherwise conducive for strengthening for at least a day or two. Octave's relatively small size could make it susceptible to relatively quick changes in intensity, up or down. All of the traditional dynamical intensity models forecast that Octave will change little in strength during that period. On the other hand, Google DeepMind (GDM) ensemble shows a very different story with an unusually large range of possibilities between tropical depression and major hurricane strength. The NHC forecast has not been changed, and is on the high end of the traditional guidance, but below the GDM ensemble mean. Because of this discrepancy, confidence in the intensity forecast is low, despite the fact that no changes were made to the NHC forecast with this advisory. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 13.4N 121.0W 45 KT 50 MPH 12H 04/0000Z 13.8N 122.0W 45 KT 50 MPH 24H 04/1200Z 14.4N 123.2W 45 KT 50 MPH 36H 05/0000Z 15.0N 123.9W 50 KT 60 MPH 48H 05/1200Z 15.4N 124.1W 55 KT 65 MPH 60H 06/0000Z 15.6N 123.7W 55 KT 65 MPH 72H 06/1200Z 15.7N 123.0W 50 KT 60 MPH 96H 07/1200Z 15.4N 121.2W 40 KT 45 MPH 120H 08/1200Z 15.0N 119.0W 35 KT 40 MPH $$ Forecaster D. Zelinsky
