Issued at 200 AM PDT Thu Oct 02 2025
000 WTPZ45 KNHC 020850 TCDEP5 Tropical Storm Octave Discussion Number 9 NWS National Hurricane Center Miami FL EP152025 200 AM PDT Thu Oct 02 2025 The overall satellite presentation of Octave has changed little since the previous advisory, though the previously well-defined curved banding to the south and west of the center has become more ragged in recent hours. The cyclone continues to be affected by moderate easterly shear, analyzed at around 17 kt by UW-CIMSS. This shear is restricting outflow in the eastern semicircle and keeping the low-level center near the eastern edge of the deep convection. Recent subjective Dvorak estimates from TAFB and SAB were 3.5/55 kt and 4.0/65 kt, respectively, while UW-CIMSS objective estimates have ranged from 48 to 59 kt over the past few hours. Based on a blend of these data, and with little change in the overall structure, the initial intensity is held at 55 kt. Octave is moving slightly north of due west, or 280 degrees at 7 kt. A west to west-northwest motion is expected during the next few days as the cyclone is steered along the southern flank of a subtropical ridge to its north. After day 3, Octave should slow as a longwave trough approaches from the northwest, weakening the ridge and overall steering flow. A developing disturbance or tropical cyclone offshore of the southwestern or west-central coast of Mexico is then forecast to erode the subtropical ridge to the east of Octave, causing the cyclone to turn eastward by days 4 and 5. The updated NHC forecast has been adjusted slightly southward to account for Octave’s more westward recent motion and the latest model trends. Considerable along- and cross-track spread remains in the extended range, and the forecast track represents a blend of the multi-model consensus and AI-based guidance. Octave will remain over warm water and within a moist environment during the next few days. However, vertical wind shear is expected to fluctuate between moderate and strong levels during the next 36 hours, which should prevent significant intensification. As a result, little change in strength is forecast during this period. Some modest strengthening is possible between 48 and 96 hours as shear decreases, though cooling sea surface temperatures and gradually drier mid-level air should limit intensification. Octave is still forecast to reach hurricane strength by days 3 and 4, remaining below some of the more aggressive hurricane regional model solutions. By day 5, weakening is likely as Octave moves into a more stable, drier air mass and encounters increasing southeasterly shear. The forecast remains close to the previous one and lies near the higher end of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 12.1N 117.9W 55 KT 65 MPH 12H 02/1800Z 12.3N 118.6W 55 KT 65 MPH 24H 03/0600Z 12.8N 119.8W 55 KT 65 MPH 36H 03/1800Z 13.3N 121.1W 55 KT 65 MPH 48H 04/0600Z 13.9N 122.4W 55 KT 65 MPH 60H 04/1800Z 14.4N 123.5W 60 KT 70 MPH 72H 05/0600Z 14.9N 124.0W 65 KT 75 MPH 96H 06/0600Z 15.6N 123.4W 65 KT 75 MPH 120H 07/0600Z 15.6N 121.1W 50 KT 60 MPH $$ Forecaster Jelsema (CPHC)
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