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Tropical Storm Hernan Discussion Number   7
NWS National Hurricane Center Miami FL       EP132020
300 PM MDT Thu Aug 27 2020
 
Hernan has had a rather ragged appearance today with intermittent 
convection firing around, but never really over the center. There 
were no ASCAT overpasses during the day that directly sampled the 
system's circulation. The latest Dvorak intensity estimates from 
TAFB and SAB support 35 kt and 30 kt, respectively, while the 
UW-CIMSS ADT and SATCON numbers range from 30 to 40 kt. Based on a 
blend of these values, the initial intensity is being lowered to 35 
kt.
 
Hernan should at least maintain its current strength through 
tonight as it remains over very warm waters while battling moderate
easterly shear. This shear is not forecast to abate during the
forecast period. And by 24 h, the cyclone is expected to begin
moving over progressively cooler waters. The combination of these
two factors should induce a weakening trend. By 60 h, simulated
satellite imagery by global models suggest that the cyclone will
become devoid of deep convection. After that time, the remnant low
is expected to be absorbed within the broader circulation of
Iselle to its west. The latest NHC intensity forecast is in 
agreement with the various intensity consensus aids.
 
Hernan is now moving northwest at about 5 kt. There is no change to 
the track forecast reasoning. Hernan is expected to remain caught 
within a large-scale, eastern North Pacific cyclonic gyre during the 
next few days, which will result in Hernan moving counter-clockwise 
around the eastern and northern periphery of the gyre. The cyclone 
is expected to continue to parallel the coast of southwestern Mexico 
through this evening and should begin to increase its forward speed 
tonight. A turn to the west-northwest then west is forecast Friday 
through Friday night. The westward motion should continue until the 
system becomes absorbed early next week.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/2100Z 19.6N 106.5W   35 KT  40 MPH
 12H  28/0600Z 20.7N 107.6W   35 KT  40 MPH
 24H  28/1800Z 21.6N 109.4W   30 KT  35 MPH
 36H  29/0600Z 22.3N 111.1W   30 KT  35 MPH
 48H  29/1800Z 22.5N 113.0W   25 KT  30 MPH
 60H  30/0600Z 22.6N 114.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  30/1800Z...ABSORBED
 
$$
Forecaster Latto
 
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