Issued at 200 AM MST Wed Oct 01 2025
000 WTPZ45 KNHC 010853 TCDEP5 Tropical Storm Octave Discussion Number 5 NWS National Hurricane Center Miami FL EP152025 200 AM MST Wed Oct 01 2025 The satellite presentation of Octave has improved during the past several hours, with a well-defined curved band now wrapping more than halfway around the low-level center. This improvement in structure appears to be due to a decrease in vertical wind shear, which has lessened to around 16 kt according to the latest UW-CIMSS analysis. The most recent subjective Dvorak intensity estimates from TAFB and SAB also indicate a stronger system, both coming in at 3.5/55 kt, while the UW-CIMSS objective estimates are lower, ranging between 33 and 40 kt since the previous advisory. Based on a blend of these data, and considering the improved satellite presentation, the initial intensity has been raised to 50 kt for this advisory, which may be conservative. Octave is estimated to be moving north-northwestward, or 335 degrees at 6 kt. This general motion is expected to continue today as the cyclone moves into a weakness in the subtropical ridge created by a disturbance to its north. Once that disturbance is absorbed by Octave’s circulation, a mid-level ridge is forecast to become re-established to the north of the cyclone, steering it westward to west-northwestward from tonight through Saturday. By 120 hours, Octave is expected to slow considerably and turn eastward as a longwave trough approaches from the northwest and the subtropical ridge to its east is eroded by a developing tropical cyclone offshore of southwestern Mexico. The new NHC track forecast has been shifted west of the previous one to account for the delay in the cyclone turning toward the north-northwest and to better match the latest guidance trends. The forecast lies near the middle of the guidance envelope and is close to a blend of the GDMI, FSSE, TVCE, and HCCA track aids. Octave will remain over warm water and within a moist environment for the next several days. However, vertical wind shear is forecast to fluctuate between moderate and strong levels, which should hinder significant intensification. Some additional strengthening is possible today, followed by little change in intensity over the next few days. Modest intensification could occur by days 4 and 5 as the shear relaxes, although sea surface temperatures will be slightly cooler and the mid-level environment less moist by that time. Confidence in the intensity forecast remains low due to considerable spread among the guidance. The official forecast has been adjusted higher to account for the cyclone’s improved structure and is most closely aligned with the SHIPS and LGEM intensity aids. FORECAST POSITIONS AND MAX WINDS INIT 01/0900Z 11.1N 114.8W 50 KT 60 MPH 12H 01/1800Z 11.8N 115.2W 55 KT 65 MPH 24H 02/0600Z 12.5N 116.2W 55 KT 65 MPH 36H 02/1800Z 13.0N 117.4W 55 KT 65 MPH 48H 03/0600Z 13.4N 118.6W 55 KT 65 MPH 60H 03/1800Z 13.8N 120.1W 55 KT 65 MPH 72H 04/0600Z 14.3N 121.2W 55 KT 65 MPH 96H 05/0600Z 15.3N 122.4W 60 KT 70 MPH 120H 06/0600Z 16.0N 121.4W 60 KT 70 MPH $$ Forecaster Jelsema (CPHC)
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