Tropical Cyclone Discussion

432
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