Issued at 200 PM PDT Thu Aug 13 2026
045 WTPZ43 KNHC 132048 TCDEP3 Tropical Storm Hernan Discussion Number 4 NWS National Hurricane Center Miami FL EP082026 200 PM PDT Thu Aug 13 2026 Hernan continues to be affected by strong westerly wind shear today. After a brief increase in convection this morning, showers and thunderstorms have become displaced to the northeast and east, leaving the center of circulation almost completely exposed. An earlier scatterometer pass indicated that the storm had moved nearly due south from the previous center position and that the radius of 34 kt winds has contracted. Recent subjective and objective intensity estimates, however, range from 28-45 kt. Keeping all of this in mind, the initial intensity is maintained at 40 kt for this advisory. The storm is moving southward at around 5 kt along the southeastern periphery of a ridge building to the northwest. A gradual turn toward the southwest and then west-southwest is forecast from Friday into this weekend as Tropical Storm Lala strengthens to the west. The latest NHC forecast has been shifted slightly to the left of the previous advisory during the first 24 h and sped up somewhat beyond 24 h through the remainder of the forecast period. Considerable spread persists among the track guidance, so confidence in the track forecast remains below average. Although Hernan remains over warm 27-28 C waters and within a fairly moist mid-level environment, strong westerly shear is expected to support gradual weakening tonight. By early Friday, increasingly dry mid-level air and decreasing upper-level divergence should further inhibit the storm's organization. The ECMWF and GFS simulated satellite imagery suggest that Hernan may struggle to maintain organized convection on 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 13/2100Z 17.3N 131.9W 40 KT 45 MPH 12H 14/0600Z 16.8N 132.0W 35 KT 40 MPH 24H 14/1800Z 16.2N 132.4W 30 KT 35 MPH 36H 15/0600Z 15.9N 133.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 15/1800Z 15.4N 135.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 16/0600Z 15.0N 136.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 16/1800Z...DISSIPATED $$ Forecaster Adams
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