Issued at 800 AM PDT Thu Aug 13 2026
738 WTPZ43 KNHC 131443 TCDEP3 Tropical Storm Hernan Discussion Number 3 NWS National Hurricane Center Miami FL EP082026 800 AM PDT Thu Aug 13 2026 Convection has increased to the north and east of the center of Hernan this morning. An earlier GPM microwave pass, which became available after the previous advisory, suggested that the center was farther southeast than previously analyzed, and the initial position for this advisory was adjusted accordingly. In addition, a recent scatterometer pass indicated peak winds of 37-39 kt in the western semicircle of the storm. The microwave imagery depicted a compact center with a well-established band wrapping around the northern and eastern portions of the circulation. Objective and subjective intensity estimates range from 28-38 kt. Given the improved satellite presentation and the scatterometer-derived winds, the initial intensity has been set at 40 kt for this advisory. Hernan is drifting slowly southwestward. A slow southwestward to southward motion is expected over the next 24-36 h as a ridge builds to the northwest of the storm and Tropical Storm Lala strengthens to the southwest. The latest NHC track forecast has been nudged slightly to the left of the previous forecast through 36 h to account for the adjusted initial position and lies between the previous forecast and HCCA. Beyond 36 h, Hernan is expected to turn toward the west-southwest and accelerate. Considerable spread remains among the track guidance, so confidence in the track forecast is a little below average. The storm is currently over warm SSTs of around 27-28 C and within a moist mid-level airmass. However, it is being impacted by strong westerly wind shear. Little change in intensity is expected over the next 12 h or so, followed by gradual weakening as Hernan encounters increasingly dry mid-level air and decreasing upper-level divergence. The ECMWF and GFS simulated satellite imagery suggest that Hernan may struggle to maintain organized convection by Friday, and the latest forecast calls for the system to degenerate to a remnant low by 36 h. The post-tropical low is expected to gradually spin down, open into a trough, and dissipate in a few days. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 18.0N 131.9W 40 KT 45 MPH 12H 14/0000Z 17.6N 132.0W 40 KT 45 MPH 24H 14/1200Z 17.1N 132.1W 35 KT 40 MPH 36H 15/0000Z 16.5N 132.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 15/1200Z 15.9N 133.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 16/0000Z 15.5N 135.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 16/1200Z...DISSIPATED $$ Forecaster Adams/Kelly
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