331
WTPZ44 KNHC 232032
TCDEP4
TROPICAL STORM ISELLE DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092026
200 PM PDT SUN AUG 23 2026
RECENT SATELLITE IMAGERY OVER ISELLE SHOWS A SHEAR PATTERN, WITH A
LARGE AREA OF VERY DEEP CONVECTION LOCATED IN THE SOUTHWEST
SEMICIRCLE OF ISELLE. VISIBLE IMAGERY SHOWS A PARTIALLY EXPOSED
LOW-LEVEL CENTER AT THE NORTHEAST EDGE OF THE CONVECTION. A RECENT
23/1748Z ASCAT-C OVERPASS SHOWS AN ELONGATED, BUT WELL-DEFINED
SURFACE CIRCULATION, WITH A RADIUS OF MAXIMUM WINDS (RMW) OF ABOUT
70 NAUTICAL MILES, WITH GALES IN THE NE, SE AND SW QUADRANTS. THERE
ARE SEVERAL 40-45 KT VECTORS ON THE SOUTH SIDE, AND THE INTENSITY IS
INCREASED TO 45 KT FOR THIS ADVISORY. THIS IS ABOVE THE LATEST
SUBJECTIVE DVORAK ESTIMATE FROM TAFB, WHICH IS T2.5/35 KT.
THE INITIAL MOTION ESTIMATE IS NORTHWESTWARD, OR 315 DEGREES AT 14
KT. A CONTINUED NORTHWEST MOTION IS EXPECTED THROUGH MONDAY WHILE
ISELLE IS STEERED BY RIDGING OVER THE SOUTHWESTERN UNITED STATES AND
NORTHWESTERN MEXICO. AS THE RIDGE BUILDS IN A BIT MORE TO THE NORTH
OF THE CYCLONE, A GRADUAL TURN TOWARD THE WEST-NORTHWEST IS EXPECTED
ON TUESDAY AND WEDNESDAY. THE NHC TRACK FORECAST HAS BEEN SHIFTED
WELL TO THE RIGHT (OR NORTHEAST) OF THE PREVIOUS FORECAST THROUGH 48
H, MAINLY DUE TO THE FARTHER NORTH INITIAL POSITION AND IS NEARLY ON
TOP OF THE PREVIOUS FORECAST THEREAFTER. THE NHC FORECAST IS VERY
CLOSE TO THE LATEST HFIP CORRECTED CONSENSUS (HCCA) MODEL AND THE
GOOGLE DEEPMIND (GDMI). THERE IS STILL A HEALTHY AMOUNT OF SPREAD
IN THE TRACK GUIDANCE, AND CONFIDENCE IN THE TRACK FORECAST 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. THEREAFTER, ISELLE WILL BE MOVING INTO A MORE
STABLE ENVIRONMENT, WITH GRADUALLY DECREASING SEA-SURFACE
TEMPERATURES, SO WEAKENING IS EXPECTED TO BEGIN BY TUESDAY NIGHT
OR WEDNESDAY. ONLY SMALL CHANGES HAVE BEEN MADE TO THE NHC
INTENSITY FORECAST, WHICH LIES BETWEEN THE MIDDLE AND HIGH END OF
THE GUIDANCE ENVELOPE FOR MOST OF THE FORECAST PERIOD. RAPID
INTENSIFICATION IS BECOMING LESS LIKELY BECAUSE THE RMW IS STILL
LARGE, AND THE SYSTEM HAS AT MOST 36-48 H LEFT TO STRENGTHEN.
FORECAST POSITIONS AND MAX WINDS
INIT 23/2100Z 16.9N 115.1W 45 KT 50 MPH
12H 24/0600Z 18.2N 116.3W 50 KT 60 MPH
24H 24/1800Z 19.6N 117.8W 60 KT 70 MPH
36H 25/0600Z 20.8N 119.4W 65 KT 75 MPH
48H 25/1800Z 21.4N 121.1W 65 KT 75 MPH
60H 26/0600Z 21.9N 122.8W 60 KT 70 MPH
72H 26/1800Z 22.4N 124.6W 50 KT 60 MPH
96H 27/1800Z 23.3N 128.4W 45 KT 50 MPH
120H 28/1800Z 24.2N 132.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
FORECASTER HAGEN
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