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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