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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