943
WTPZ45 KNHC 081437
TCDEP5
TROPICAL STORM SIMON DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202026
900 AM CST THU OCT 08 2026
SIMON CONTINUES TO STEADILY BECOME BETTER ORGANIZED. SATELLITE AND
MICROWAVE IMAGES INDICATE THAT THE STORM HAS A COMPACT INNER CORE
AND MUCH LARGER RAINBANDS SURROUNDING IT. THE OUTER BANDS ON THE
NORTHEAST SIDE OF THE CIRCULATION ARE MOVING ACROSS COASTAL AREAS OF
SOUTHWESTERN MEXICO, LIKELY BRINGING HEAVY RAINS AND GUSTY WINDS
THERE. THE LATEST SATELLITE INTENSITY ESTIMATES RANGE FROM 45 TO 55
KT, AND THE INITIAL INTENSITY IS SET AT THE HIGH END OF THE
ESTIMATES AT 55 KT.
THE TROPICAL STORM IS MOVING SLOWLY WESTWARD AT ABOUT 5 KT, STEERED
BY A WEAK MID-LEVEL RIDGE TO ITS NORTH. A CONTINUED SLOW WEST TO
WEST-NORTHWEST MOTION IS EXPECTED THROUGH TONIGHT AS THAT RIDGE
REMAINS IN PLACE. HOWEVER, A SHARP TURN TO THE NORTH IS FORECAST ON
FRIDAY WHEN THE RIDGE WEAKENS AND SHIFTS EASTWARD, IN RESPONSE TO AN
APPROACHING MID- TO UPPER-LEVEL TROUGH. ALTHOUGH THE MODELS
GENERALLY AGREE ON THE LARGE-SCALE STEERING PATTERN EVOLUTION,
THERE ARE VERY IMPORTANT DIFFERENCES IN WHERE AND WHEN THE SYSTEM
MAKES THAT TURN. MOST OF THE AI MODELS, INCLUDING GFSAI, ECAI, AND
GDMI SHOW THE TURN OCCURRING WELL EAST OF THE PHYSICS-BASED MODELS.
SINCE THE PHYSICS-BASED MODELS HAVE OFTEN HAD A WESTWARD BIAS IN
THIS REGION, THE NHC TRACK FORECAST HAS BEEN NUDGED EASTWARD TO BE
IN BETTER AGREEMENT WITH THE LATEST AI GUIDANCE. THIS FORECAST
BRINGS THE CORE OF THE SYSTEM INLAND OVER SOUTHWESTERN AND
WEST-CENTRAL MEXICO SATURDAY NIGHT OR EARLY SUNDAY.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE QUITE CONDUCIVE FOR
STRENGTHENING, INCLUDING LOW WIND SHEAR, VERY WARM WATERS, AND HIGH
MOISTURE. BASED ON THESE FAVORABLE CONDITIONS AND THE COMPACT
INNER CORE STRUCTURE, RAPID INTENSIFICATION IS FORECAST, AND SIMON
IS EXPECTED TO BECOME A HURRICANE LATER TODAY AND A VERY DANGEROUS
CATEGORY 4 HURRICANE BEFORE IT REACHES THE COAST OF MEXICO. THIS
FORECAST LIES NEAR THE HIGH END OF THE GUIDANCE, IN BEST AGREEMENT
WITH THE HCCA MODEL.
BASED ON THE LATEST FORECAST, THE GOVERNMENT OF MEXICO HAS ISSUED A
HURRICANE WATCH FOR PORTIONS OF WEST-CENTRAL MEXICO.
KEY MESSAGES:
1. SIMON IS EXPECTED TO STRENGTHEN TO A HURRICANE LATER TODAY AND
APPROACH THE WEST-CENTRAL COAST OF MEXICO AS A MAJOR HURRICANE ON
SATURDAY AND SATURDAY NIGHT.
2. THE RISK OF LIFE-THREATENING WIND AND STORM SURGE IMPACTS IS
INCREASING FOR PORTIONS OF THE WEST-CENTRAL COAST OF MEXICO, AND A
HURRICANE WATCH IS NOW IN EFFECT FROM MANZANILLO TO PUNTA MITA.
PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE COMPLETED BY
SATURDAY.
3. HEAVY RAINFALL ASSOCIATED WITH SIMON WILL IMPACT PORTIONS OF
SOUTHWESTERN MEXICO THROUGH THIS WEEKEND. THIS RAINFALL MAY PRODUCE
LIFE-THREATENING FLOODING AND MUDSLIDES, ESPECIALLY IN AREAS OF
STEEP TERRAIN.
4. SWELLS WILL AFFECT PORTIONS OF THE SOUTHWESTERN AND WEST-CENTRAL
COAST OF MEXICO THROUGH THE WEEKEND. THESE SWELLS ARE LIKELY TO
CAUSE LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. PLEASE
CONSULT PRODUCTS FROM YOUR LOCAL WEATHER OFFICE.
FORECAST POSITIONS AND MAX WINDS
INIT 08/1500Z 15.4N 103.3W 55 KT 65 MPH
12H 09/0000Z 15.5N 104.1W 70 KT 80 MPH
24H 09/1200Z 16.1N 104.9W 85 KT 100 MPH
36H 10/0000Z 16.9N 105.1W 100 KT 115 MPH
48H 10/1200Z 17.6N 105.1W 115 KT 130 MPH
60H 11/0000Z 18.7N 105.1W 115 KT 130 MPH
72H 11/1200Z 19.7N 105.1W 115 KT 130 MPH...INLAND
96H 12/1200Z 22.2N 105.6W 65 KT 75 MPH...INLAND
120H 13/1200Z 25.1N 106.0W 30 KT 35 MPH...POST-TROP/INLAND
FORECASTER CANGIALOSI
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