519
WTPZ44 KNHC 260232
TCDEP4
TROPICAL STORM ISELLE DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092026
800 PM PDT TUE AUG 25 2026
SATELLITE IMAGERY INDICATES THAT ISELLE CONTINUES TO BE SHEARED AND
THAT THE LOW-LEVEL CIRCULATION IS BECOMING MORE DETACHED FROM THE
MID-LEVEL CENTER. AS SUCH, THE DEEP CONVECTION IS STILL LOCATED AWAY
FROM THE CENTER OF THE STORM, WHICH IS A STRONG INDICATION THAT THE
CYCLONE IS CONTINUING TO WEAKEN. WATER VAPOR IMAGERY ALSO SHOWS THAT
DRY AIR IS INTRUDING FAR INTO THE CORE OF THE CYCLONE AS WELL. WHILE
THE MOST RECENT SUBJECTIVE DVORAK INTENSITY ESTIMATE FROM TAFB WAS
AT CI 3.5/55 KT, THE OBJECTIVE UW-CMISS ESTIMATES ARE LOWER AND
RANGE FROM 33-45 KT. THUS, BASED ON THE AVAILABLE DATA, THE INITIAL
INTENSITY HAS BEEN SET TO 45 KT FOR THIS ADVISORY.
FURTHER WEAKENING IS ANTICIPATED DUE TO CONTINUED SHEAR,
PROGRESSIVELY COOLER WATER AND INCREASING DRY AIR ENTRAINMENT NEAR
THE CORE OF THE CYCLONE. THE GFS AND ECMWF SIMULATED SATELLITE
IMAGERY SHOW THE CYCLONE BECOMING DEVOID OF ORGANIZED DEEP
CONVECTION IN 24 TO 36 H. GIVEN THE CURRENT APPEARANCE OF THE
STORM, IT IS POSSIBLE THAT ISELLE COULD BECOME A POST-TROPICAL
REMNANT LOW SOONER AND DISSIPATE FASTER THAN INDICATED IN THE
FORECAST. THE CURRENT NHC INTENSITY FORECAST IS VERY SIMILAR TO THE
PREVIOUS ONE, WITH MINOR ADJUSTMENTS TOWARDS THE END OF THE
FORECAST PERIOD.
TRENDS FROM THE MOST RECENT SATELLITE FIXES SHOW THAT THE ISELLE
CONTINUES TO MOVE TO THE WEST-NORTHWEST AROUND 7 KT. A RIDGE FROM
THE SOUTHERN UNITED STATES IS EXPECTED TO EXTEND WESTWARD AND SHOULD
KEEP THE SYSTEM MOVING TOWARDS THE WEST-NORTHWEST. AS THE STORM
WEAKENS, IT SHOULD TURN MORE WESTWARD DUE TO THE LOW-LEVEL FLOW
STEERING THE SHALLOW CYCLONE. THE CURRENT NHC TRACK IS VERY SIMILIAR
TO THE PREVIOUS TRACK, WITH ONLY SLIGHT ADJUSTMENTS TO THE PREVIOUS
FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 26/0300Z 21.3N 122.5W 45 KT 50 MPH
12H 26/1200Z 21.6N 123.7W 40 KT 45 MPH
24H 27/0000Z 22.3N 125.5W 35 KT 40 MPH
36H 27/1200Z 22.9N 127.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 28/0000Z 23.4N 129.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 28/1200Z 23.8N 131.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 29/0000Z...DISSIPATED
FORECASTER KATZ/PAPIN
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