233
WTPZ45 KNHC 260335 CCA
TCDEP5
TROPICAL STORM JOHN DISCUSSION NUMBER 13...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL EP102024
900 PM CST WED SEP 25 2024
CORRECTED HURRICANE TO TROPICAL STORM JOHN
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT JUST FINISHED ITS
INVESTIGATION OF TROPICAL STORM JOHN AND FOUND THAT THE CENTRAL
PRESSURE HAS DROPPED TO 984 MB. DROPSONDE DATA AND SFMR DATA
SUPPORT AN INTENSITY OF 55 KT, WHICH IS ALSO THE AVERAGE OF THE
LATEST TAFB AND SAB INTENSITY ESTIMATES. SATELLITE IMAGERY SHOWS A
VERY LARGE AREA OF VERY COLD CLOUD TOPS. BASED ON THE AVAILABLE
DATA, THE INITIAL INTENSITY IS INCREASED TO 55 KT.
BASED ON FIXES FROM THE AIR FORCE PLANE, THE INITIAL MOTION IS
ESTIMATED TO BE NORTHWESTWARD, OR 325/4 KT. THE MODEL GUIDANCE HAS
MADE A BIG SHIFT TO THE WEST ON THIS CYCLE, WHICH MAKES SENSE SINCE
JOHN HAS BEEN MOVING SIGNIFICANTLY TO THE WEST OF THE PREVIOUS NHC
FORECAST TRACK. THE NEW NHC TRACK FORECAST HAS BEEN SHIFTED WELL
TO THE WEST, AND CURRENTLY LIES SLIGHTLY TO THE EAST OF THE LATEST
TRACK CONSENSUS AIDS. THE WESTWARD SHIFT TO THE TRACK HAS
NECESSITATED THE HURRICANE WARNINGS TO BE SHIFTED FARTHER WEST
ALONG THE COAST OF MEXICO. THE NEW FORECAST SHOWS LANDFALL
OCCURRING ABOUT 40 TO 50 MILES FARTHER TO THE WEST COMPARED TO THE
PREVIOUS OFFICIAL FORECAST, WITH THE FORECAST LANDFALL NOW WELL TO
THE WEST OF LAZARO CARDENAS LATER THURSDAY NIGHT. IT SHOULD BE
NOTED THAT THERE IS STILL QUITE A BIT OF UNCERTAINTY IN THE TRACK
FORECAST.
TROPICAL STORM JOHN IS CURRENTLY LOCATED OVER 31C SEA-SURFACE
TEMPERATURES, WHICH IS EXTREMELY WARM. THE TROPICAL STORM IS ALSO
IN A MOIST ENVIRONMENT AND APPEARS TO ALSO HAVE A FAVORABLE
UPPER-LEVEL WIND ENVIRONMENT. BOTH THE GFS-SHIPS AND THE
ECMWF-SHIPS RAPID-INTENSITY-INDEX SHOWS A VERY HIGH CHANCE OF RAPID
INTENSIFICATION OVER THE NEXT 24 HOURS. THE NEW NHC INTENSITY
FORECAST HAS BEEN INCREASED SIGNIFICANTLY FROM THE PREVIOUS OFFICIAL
FORECAST, AND LIES NEAR THE HIGH END OF THE LATEST INTENSITY
GUIDANCE SUITE. GIVEN THE EXTREMELY FAVORABLE ENVIRONMENTAL
CONDITIONS, IT WOULDN'T BE SURPRISING IF FURTHER INCREASES TO THE
INTENSITY FORECAST ARE NEEDED ON SUBSEQUENT FORECASTS.
ALTHOUGH THIS FORECAST SHOWS DISSIPATION BY HOUR 60, THERE IS A
CHANCE THAT JOHN COULD SURVIVE A BIT LONGER, MOVING
WEST-NORTHWESTWARD NEAR THE COAST OF MEXICO.
IT CANNOT BE EMPHASIZED ENOUGH THAT CATASTROPHIC LIFE-THREATENING
FLASH FLOODING AND MUDSLIDES ARE EXPECTED TO CONTINUE THROUGH THE
END OF THE WEEK FOR PORTIONS OF THE MEXICAN STATES OF GUERRERO,
OAXACA AND MICHOACAN.
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,
OAXACA AND MICHOACAN.
2. JOHN IS FORECAST TO STRENGTHEN TO A HURRICANE BEFORE LANDFALL,
AND THE HURRICANE WARNING HAS BEEN EXTENDED WESTWARD ALONG THE
COASTLINE OF SOUTHWESTERN MEXICO, WHERE TROPICAL STORM CONDITIONS
COULD BEGIN WITHIN THE NEXT FEW HOURS. TROPICAL STORM WARNINGS ARE
ALSO IN EFFECT FOR PORTIONS OF THE AREA.
FORECAST POSITIONS AND MAX WINDS
INIT 26/0300Z 17.0N 102.1W 55 KT 65 MPH
12H 26/1200Z 17.3N 102.3W 65 KT 75 MPH
24H 27/0000Z 17.7N 102.5W 80 KT 90 MPH
36H 27/1200Z 18.1N 102.7W 70 KT 80 MPH...INLAND
48H 28/0000Z 18.4N 103.2W 30 KT 35 MPH...INLAND
60H 28/1200Z...DISSIPATED
FORECASTER HAGEN
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