579
WTPZ44 KNHC 242032
TCDEP4
TROPICAL STORM ISELLE DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092026
200 PM PDT MON AUG 24 2026
ISELLE'S CLOUD PATTERN CONTINUES TO GRADUALLY IMPROVE IN
GEOSTATIONARY SATELLITE IMAGERY DESPITE THE MODERATE
WEST-NORTHWESTERLY SHEAR IN THE ENVIRONMENT. THE CYCLONE CONTAINS A
CORE OF DEEP CONVECTION WITH AN IMPRESSIVE TRAILING CURVED BAND
EXTENDING SOUTHWARD ON THE EAST SIDE OF ISELLE. SOME RECENT
MICROWAVE SATELLITE OVERPASSES SHOW A SIMILAR STRUCTURE. THE LATEST
SUBJECTIVE DVORAK CLASSIFICATION FROM TAFB IS T3.5/55 KT, AND
OBJECTIVE SATELLITE INTENSITY ESTIMATES RANGE FROM 55 TO 59 KT.
BASED ON THE IMPROVING STRUCTURE, THE INITIAL INTENSITY IS INCREASED
TO 60 KT FOR THIS ADVISORY.
THE INITIAL MOTION ESTIMATE IS UNCHANGED FROM THE PREVIOUS ADVISORY,
NORTHWESTWARD, OR 310/11 KT. A MID-LEVEL RIDGE NORTH OF ISELLE IS
FORECAST TO STRENGTHEN, CAUSING ISELLE TO TURN WEST-NORTHWESTWARD ON
TUESDAY, AND THAT MOTION SHOULD THEN CONTINUE THROUGH THE END OF THE
WEEK. THE LATEST NHC TRACK FORECAST IS QUITE SIMILAR TO THE
PREVIOUS ONE, AND LIES VERY CLOSE TO THE HFIP CORRECTED CONSENSUS
(HCCA) AND THE GOOGLE DEEPMIND ENSEMBLE MEAN (GDMI).
ISELLE REMAINS OVER WARM WATERS AND WITHIN A MOIST ENVIRONMENT.
HOWEVER, THE CYCLONE IS EXPERIENCING MODERATE WEST-NORTHWESTERLY
VERTICAL WIND SHEAR. WATER TEMPERATURES AND MOISTURE WILL REMAIN
QUITE FAVORABLE FOR ANOTHER 12 TO 24 H, BUT THE SHEAR IS FORECAST TO
INCREASE SLIGHTLY TO ABOUT 20 KT IN ABOUT 12 H. GIVEN THE RECENTLY
IMPROVING STRUCTURE, THE NHC FORECAST CONTINUES TO CALL FOR THE
SYSTEM TO STRENGTHEN TO A HURRICANE IN 12 H. THE NHC INTENSITY
FORECAST IS NEAR THE HIGH END OF THE GUIDANCE SUITE FOR THE FIRST 36
H OF THE FORECAST. BEYOND 24 H, GRADUALLY DECREASING OCEAN
TEMPERATURES AND MOISTURE WILL LEAD TO STEADY WEAKENING, AND THE NHC
INTENSITY FORECAST LIES IN THE MIDDLE OF THE GUIDANCE ENVELOPE FROM
HOUR 48 ONWARD. THE LATEST ECMWF AND GFS SIMULATED SATELLITE IMAGERY
SUGGEST THAT ISELLE COULD BECOME A REMNANT LOW AS EARLY AS THURSDAY.
THE TIME OF WHEN ISELLE BECOMES A POST-TROPICAL CYCLONE HAS BEEN
MOVED FORWARD TO 72 HOURS. AFTER THAT, THE MODELS INDICATE THE
REMNANT LOW OPENING UP INTO A TROUGH BETWEEN DAY 4 AND 5.
FORECAST POSITIONS AND MAX WINDS
INIT 24/2100Z 19.2N 118.0W 60 KT 70 MPH
12H 25/0600Z 20.1N 119.4W 65 KT 75 MPH
24H 25/1800Z 20.9N 121.3W 60 KT 70 MPH
36H 26/0600Z 21.4N 123.2W 55 KT 65 MPH
48H 26/1800Z 21.9N 124.9W 45 KT 50 MPH
60H 27/0600Z 22.4N 126.8W 35 KT 40 MPH
72H 27/1800Z 22.9N 128.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 28/1800Z 23.5N 133.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 29/1800Z...DISSIPATED
FORECASTER HAGEN
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