268
WTPZ44 KNHC 250843
TCDEP4
TROPICAL STORM ISELLE DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092026
200 AM PDT TUE AUG 25 2026
THE INFRARED SATELLITE PRESENTATION OF ISELLE REMAINS STEADY EARLY
THIS MORNING, FEATURING AN ESTABLISHED CURVED BAND WITH VERY COLD
CLOUD TOPS OF -75C TO -80C THAT WRAPS ABOUT HALFWAY AROUND THE
STORM. MODERATE WESTERLY WIND SHEAR CONTINUES TO IMPACT THE SYSTEM.
EARLIER MICROWAVE IMAGERY SHOWED AN ESTABLISHED CORE NORTH AND EAST
OF THE CENTER, ALTHOUGH THE WESTERN PORTION OF THE CIRCULATION WAS
LESS DEFINED. AN ASCAT-B PASS FROM EARLIER TONIGHT INDICATED MAXIMUM
WINDS OF 53-56 KT, ALONG WITH SLIGHTLY LARGER 34-KT WIND RADII IN
THE NORTHEAST, SOUTHEAST AND NORTHWEST QUADRANTS. RECENT OBJECTIVE
AND SUBJECTIVE DVORAK INTENSITY ESTIMATES RANGE FROM 51-63 KT. GIVEN
THE STEADY SATELLITE PRESENTATION AND ASCAT DATA, AND AFTER BLENDING
THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES, THE INITIAL
INTENSITY IS MAINTAINED AT 60 KT FOR THIS ADVISORY. THE ASCAT DATA
ALSO INDICATED THAT ISELLE IS LOCATED FARTHER NORTHWEST AND MOVING
SLIGHTLY FASTER THAN PREVIOUSLY ESTIMATED.
THE TROPICAL STORM IS MOVING NORTHWESTWARD AROUND 13 KT. A TURN
TOWARD THE WEST-NORTHWEST, ACCOMPANIED BY A SLIGHT DECREASE IN
FORWARD SPEED, IS EXPECTED LATER TODAY AS MID-LEVEL RIDGING
CURRENTLY CENTERED OVER THE SOUTHERN UNITED STATES STRENGTHENS AND
EXPANDS WESTWARD INTO THE EASTERN PACIFIC. THIS GENERAL HEADING IS
EXPECTED TO CONTINUE OVER THE NEXT SEVERAL DAYS. THE LATEST NHC
TRACK FORECAST HAS BEEN SHIFTED SLIGHTLY TO THE LEFT AND IS FASTER
THAN THE PREVIOUS ADVISORY TO ACCOUNT FOR THE ADJUSTMENT TO THE
INITIAL POSITION. THE FORECAST REMAINS NEAR THE MIDDLE OF THE TRACK
GUIDANCE ENVELOPE AND IS CLOSEST TO THE GOOGLE DEEPMIND ENSEMBLE
MEAN (GDMI).
ISELLE IS CURRENTLY MOVING OVER WARM WATERS NEAR 28 C AND REMAINS
WITHIN A RELATIVELY MOIST MID-LEVEL ENVIRONMENT, AND HAS LIKELY
REACHED ITS PEAK INTENSITY. AS THE STORM MOVES WEST-NORTHWESTWARD,
PROGRESSIVELY COOLER WATERS, INCREASING DRY MID-LEVEL AIR, CONTINUED
WESTERLY WIND SHEAR AND INCREASINGLY UNFAVORABLE UPPER-LEVEL WINDS
ARE EXPECTED TO CAUSE GRADUAL WEAKENING OVER THE NEXT SEVERAL
DAYS. THE LATEST NHC INTENSITY FORECAST CALLS FOR ISELLE TO WEAKEN
TO A TROPICAL DEPRESSION BY 60 H, AND A POST-TROPICAL REMNANT LOW BY
72 H. HOWEVER, THE ECMWF AND GFS SIMULATED SATELLITE IMAGERY SUGGEST
THAT ISELLE COULD STRUGGLE TO MAINTAIN ORGANIZED DEEP CONVECTION
BEFORE THAT TIME, RAISING THE POSSIBILITY THAT THE CYCLONE COULD
BECOME POST-TROPICAL EARLIER THAN CURRENTLY FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 25/0900Z 20.7N 119.9W 60 KT 70 MPH
12H 25/1800Z 21.3N 121.4W 55 KT 65 MPH
24H 26/0600Z 21.9N 123.2W 50 KT 60 MPH
36H 26/1800Z 22.7N 124.9W 45 KT 50 MPH
48H 27/0600Z 23.4N 126.8W 35 KT 40 MPH
60H 27/1800Z 23.9N 128.8W 30 KT 35 MPH
72H 28/0600Z 24.3N 130.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 29/0600Z...DISSIPATED
FORECASTER ADAMS
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