613
WTPZ45 KNHC 161457
TCDEP5
TROPICAL STORM SIMON DISCUSSION NUMBER 37
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202026
800 AM MST FRI OCT 16 2026
SOUTHWESTERLY VERTICAL WIND SHEAR AND DRY MID-LEVEL AIR ARE TAKING A
TOLL ON SIMON THIS MORNING. AN EARLIER AMSR-3 MICROWAVE PASS
INDICATED THAT THE MID-LEVEL CENTER WAS DISPLACED TO THE NORTHEAST
OF THE LOW-LEVEL CENTER, A TREND ALSO REFLECTED IN BURSTS OF DEEP
CONVECTION TO THE NORTH AND EAST OF THE CENTER OVER THE PAST
SEVERAL HOURS. THE PASS ALSO SUGGESTED THAT THE LOW-LEVEL CENTER
WAS SLIGHTLY FARTHER NORTH THAN PREVIOUSLY ESTIMATED, AND THE
INITIAL POSITION WAS ADJUSTED ACCORDINGLY. THE LATEST TAFB DVORAK
INTENSITY ESTIMATE WAS 2.0/30 KT. HOWEVER, CONVECTIVE ORGANIZATION
HAS CHANGED LITTLE, SO THE INTENSITY IS MAINTAINED AT 35 KT FOR THIS
ADVISORY.
SIMON IS MOVING NORTHWESTWARD AT 315/8 KT. GIVEN THE STORM'S SHALLOW
NATURE, ITS MOTION IS BEING STEERED BY THE LOW- AND MID-LEVEL FLOW,
CHARACTERIZED BY TROUGHING TO THE WEST AND A MID-LEVEL RIDGE TO THE
NORTHEAST. THIS GENERAL MOTION IS EXPECTED TO CONTINUE OVER THE NEXT
24-36 H, BRINGING SIMON PARALLEL TO THE COAST OF BAJA CALIFORNIA
SUR. FOLLOWING THE NORTHWARD ADJUSTMENT OF THE INITIAL POSITION, THE
LATEST NHC TRACK FORECAST HAS BEEN SHIFTED SLIGHTLY TO THE RIGHT OF
THE PREVIOUS FORECAST AND LIES NEAR THE CORRECTED CONSENSUS (HCCA)
TRACK.
DESPITE MOVING OVER VERY WARM WATERS (28-30 C), SIGNIFICANT
SOUTHWESTERLY WIND SHEAR AND INCREASINGLY DRY MID-LEVEL AIR ARE
EXPECTED TO SUPPORT CONTINUED WEAKENING. IN FACT, SIMULATED
SATELLITE IMAGERY FROM THE ECMWF AND GFS SUGGEST THAT SIMON MAY
STRUGGLE TO MAINTAIN ORGANIZED DEEP CONVECTION BY LATE TONIGHT. THE
OFFICIAL FORECAST CALLS FOR SIMON TO BECOME A POST-TROPICAL REMNANT
LOW WITHIN 24 H, THOUGH THIS TRANSITION MAY OCCUR SOONER.
DISSIPATION IS EXPECTED BY 48 H.
FORECAST POSITIONS AND MAX WINDS
INIT 16/1500Z 20.6N 109.5W 35 KT 40 MPH
12H 17/0000Z 21.6N 110.9W 30 KT 35 MPH
24H 17/1200Z 22.7N 112.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 18/0000Z 24.0N 114.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 18/1200Z...DISSIPATED
FORECASTER ADAMS
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