336
WTPZ44 KNHC 240245
TCDEP4
TROPICAL STORM ISELLE DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092026
800 PM PDT SUN AUG 23 2026
THE MOST RECENT ASCAT AND OSCAT PASSES HAVE SHOWN THAT THE STRONGEST
WINDS WITH ISELLE ARE AROUND 40 TO 45 KT. UW-CIMSS OBJECTIVE
ESTIMATES ARE IN THE 35-55 KT RANGE, AND THE MOST RECENT TAFB
SUBJECTIVE DVORAK ESTIMATE IS T3.0/45 KT. WITH ALL OF THAT DATA IN
CONSIDERATION, THE INTENSITY HAS BEEN HELD AT 45 KT FOR THIS
ADVISORY. HOWEVER, RECENT OBSERVATIONS AT ISLA CLARION HAVE RECORDED
SUSTAINED WINDS AROUND 30 TO 35 KT, GUSTING UP TO AROUND 40 KT AND
A SURFACE PRESSURE OF 1002 MB. THUS IN LIGHT OF THAT DATA, THE
CENTRAL PRESSURE FOR ISELLE HAS BEEN LOWERED TO 999 MB.
THE INITIAL MOTION ESTIMATE IS NORTHWESTWARD, OR 310 DEGREES AT 8
KT. A CONTINUED NORTHWESTWARD MOTION IS EXPECTED THROUGH MONDAY
WHILE ISELLE IS STEERED BY RIDGING OVER THE SOUTHWESTERN UNITED
STATES AND NORTHWESTERN MEXICO. AS THE RIDGE BUILDS IN SOME MORE TO
THE NORTH OF THE CYCLONE, A GRADUAL TURN TOWARD THE WEST-NORTHWEST
IS EXPECTED ON TUESDAY AND WEDNESDAY. THE CURRENT NHC TRACK IS VERY
SIMILAR TO THE PREVIOUS TRACK, ONLY MINOR ADJUSTMENTS IN SPEED AND
LOCATION HAVE BEEN MADE. THE TRACK REMAINS VERY CLOSE TO THE LASTEST
HFIP CORRECTED CONSENSUS (HCCA) MODEL AND THE GOOGLE DEEPMIND
(GDMI). THERE IS A GOOD AMOUNT OF SPREAD IN THE TRACK FORECAST
TOWARDS THE LATER PORTION OF THE FORECAST, THUS THE CONFIDENCE IS
SLIGHTLY BELOW AVERAGE.
ISELLE WILL BE TRAVELING OVER WARM WATER AND WITHIN A MOIST
ENVIRONMENT WITH WEAK TO MODERATE VERTICAL WIND SHEAR FOR THE NEXT
DAY OR SO, BUT WESTERLY VERTICAL WIND SHEAR SHOULD INCREASE TO THE
15-20 KT RANGE BY TUESDAY OR SOONER. STRENGTHENING IS EXPECTED FOR
THE NEXT 36 H. THE CURRENT NHC INTENSITY FORECAST IS ON THE HIGHER
END OF THE GUIDANCE, THUS IT IS POSSIBLE THAT ISELLE MIGHT NOT QUITE
MAKE IT TO HURRICANE STATUS. AFTER THIS PERIOD, THE CYCLONE WILL
MOVE INTO A MORE HOSTILE ENVIRONMENT WITH STRONGER SHEAR, COLDER
SEA-SURFACE TEMPERATURES, AND SOME SLIGHTLY DRIER AIR. AS SUCH, THE
STORM SHOULD PROGRESSIVELY GET WEAKER BEYOND A COUPLE OF DAYS.
FORECAST POSITIONS AND MAX WINDS
INIT 24/0300Z 17.1N 115.3W 45 KT 50 MPH
12H 24/1200Z 18.1N 116.4W 50 KT 60 MPH
24H 25/0000Z 19.4N 117.8W 60 KT 70 MPH
36H 25/1200Z 20.4N 119.6W 65 KT 75 MPH
48H 26/0000Z 21.0N 121.4W 60 KT 70 MPH
60H 26/1200Z 21.5N 123.1W 55 KT 65 MPH
72H 27/0000Z 21.9N 125.1W 50 KT 60 MPH
96H 28/0000Z 22.8N 128.8W 40 KT 45 MPH
120H 29/0000Z 23.6N 132.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
FORECASTER KATZ/CANGIALOSI
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