657
WTPZ45 KNHC 270235
TCDEP5
TROPICAL STORM JOHN DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL EP102024
900 PM CST THU SEP 26 2024
THE CONVECTION NEAR THE CENTER OF JOHN HAS WEAKENED SIGNIFICANTLY
OVER THE PAST 12 HOURS. A CURVED BAND OFF TO THE SOUTHWEST AND WEST
OF JOHN'S CENTER IS PRODUCING A CONTINUOUS LARGE AREA OF DEEP
CONVECTION. SUBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES FROM TAFB
AND SAB RANGE FROM 65 TO 77 KT, BUT THE OBJECTIVE INTENSITY
ESTIMATES FROM UW-CIMSS RANGE FROM 49 TO 56 KT. SINCE THE CONVECTION
OVER THE CENTER HAS WARMED ON INFRARED IMAGERY AND APPEARS TO BE
LESS ORGANIZED OVER THE PAST 12 HOURS, THE INITIAL INTENSITY IS
BEING LOWERED TO 60 KT FOR THIS ADVISORY.
JOHN HAS BEEN MOVING NORTHWESTWARD, OR 315/4 KT, WHICH IS A BIT
FASTER THAN BEFORE. THIS SLOW MOTION IS FORECAST TO CONTINUE FOR
ANOTHER 12 TO 24 H, AS JOHN MOVES NEAR THE COASTLINE OR JUST INLAND
LATE TONIGHT AND EARLY TOMORROW. AFTER THAT, A TURN TO THE
WEST-NORTHWEST WITH SOME ACCELERATION IS FORECAST, IF JOHN SURVIVES
ITS INTERACTION WITH THE HIGHER TOPOGRAPHY IN THIS PART OF MEXICO.
THE LATEST TRACK FORECAST IS A LITTLE TO THE LEFT AND SLIGHTLY
FASTER THAN THE PREVIOUS FORECAST, AND IS VERY NEAR THE LASTEST HCCA
CORRECTED CONSENSUS AID.
IT SEEMS UNLIKELY THAT JOHN WILL BE ABLE TO RESTRENGTHEN SINCE THE
CENTER IS NOW JUST 20 MILES FROM THE COASTLINE AND IS FORECAST TO
MOVE EVEN CLOSER TO THE COAST OVER THE NEXT SEVERAL HOURS. SINCE
JOHN'S CORE HAS BEEN DISRUPTED BY THE TOPOGRAPHY TODAY, IT IS
UNLIKELY TO RECOVER, DESPITE RELATIVELY FAVORABLE ENVIRONMENTAL
CONDITIONS. LITTLE CHANGE IN STRENGTH, OR PERHAPS SLOW WEAKENING,
IS LIKELY OVER THE NEXT 12 HOURS UNTIL THE CENTER REACHES THE
COASTLINE. THEREAFTER, FASTER WEAKENING IS EXPECTED ON FRIDAY AS THE
CENTER MOVES NEAR OR ALONG THE COASTLINE. THE LATEST NHC INTENSITY
FORECAST IS NEAR THE MIDDLE OF THE INTENSITY GUIDANCE SUITE. IT IS
QUITE POSSIBLE THAT JOHN COULD WEAKEN TO A REMNANT LOW AND DISSIPATE
SOONER THAN FORECAST.
KEY MESSAGES:
1. TROPICAL STORM JOHN WILL BRING ADDITIONAL VERY HEAVY RAINFALL TO
COASTAL PORTIONS OF SOUTHWEST MEXICO THROUGH FRIDAY. THE ADDITIONAL
RAINFALL TOTALS WILL BE FALLING ACROSS AREAS THAT HAVE RECEIVED VERY
HEAVY RAINFALL AMOUNTS OVER THE PAST FEW DAYS. THIS HEAVY RAINFALL
WILL LIKELY CAUSE SIGNIFICANT AND CATASTROPHIC LIFE-THREATENING
FLASH FLOODING AND MUDSLIDES TO THE MEXICAN STATES OF GUERRERO AND
MICHOACáN.
2. JOHN IS FORECAST TO CONTINUE BRINGING TROPICAL STORM CONDITIONS
ACROSS PORTIONS OF THE TROPICAL STORM WARNINGS AREA THROUGH FRIDAY.
FORECAST POSITIONS AND MAX WINDS
INIT 27/0300Z 17.9N 103.2W 60 KT 70 MPH
12H 27/1200Z 18.3N 103.4W 55 KT 65 MPH...INLAND
24H 28/0000Z 19.0N 104.4W 35 KT 40 MPH...OVER WATER
36H 28/1200Z 19.5N 105.7W 25 KT 30 MPH
48H 29/0000Z 20.2N 107.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 29/1200Z 20.8N 108.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 30/0000Z...DISSIPATED
FORECASTER HAGEN
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