788
WTPZ45 KNHC 262039
TCDEP5
HURRICANE JOHN DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL EP102024
300 PM CST THU SEP 26 2024
JOHN HAS SLOWED ITS FORWARD MOTION THIS AFTERNOON. A SCATTEROMETER
PASS LATE THIS MORNING CONFIRMED THAT THE MOTION HAD SLOWED AND THE
CENTER IS LINGERING OFFSHORE. THE INNER CORE OF CONVECTION HAS
BECOME LESS PRONOUNCED AND THE CIRCULATION MAY BE FEELING THE
OROGRAPHIC EFFECTS OF THE MOUNTAINOUS TERRAIN OF SOUTHWESTERN
MEXICO. HOWEVER, A STRONG CONVECTIVE CURVED BAND EXTENDS IN THE
SOUTHWEST SEMI-CIRCLE. DVORAK SATELLITE INTENSITY ESTIMATES HAVE
REMAINED FAIRLY STEADY THIS AFTERNOON BETWEEN 65 TO 75 KT. GIVEN THE
CURRENT SATELLITE INTENSITY ESTIMATES, THE INITIAL INTENSITY FOR
THIS ADVISORY REMAINS AT 65 KT.
THE HURRICANE HAS NOT BEEN MOVING MUCH SINCE THE PREVIOUS ADVISORY
AND THE ESTIMATED MOTION IS 325/ 2 KT. THIS SLOW MOTION IS FORECAST
TO CONTINUE AS JOHN APPROACHES THE COASTLINE, MOVING ALONG THE
COAST OR JUST INLAND LATER TONIGHT OR EARLY TOMORROW. SOME OF THE
GLOBAL MODEL FIELDS KEEP THE SYSTEM OFFSHORE NEAR THE COAST A
LITTLE LONGER. IN THE LONG TERM, A TURN BACK TO THE WEST-NORTHWEST
IS ANTICIPATED AS THE SYSTEM WEAKENS AND IS STEERED BY A HIGH
PRESSURE RIDGE LOCATED OVER NORTHERN MEXICO.
THE OVERALL ENVIRONMENT REMAINS FAVORABLE FOR JOHN TO STRENGTHEN
WITH VERY WARM SEA SURFACE TEMPERATURES AND LOW WIND SHEAR.
HOWEVER, JOHN'S PROXIMITY TO THE COASTLINE MAY CONTINUE TO DISRUPT
THE CIRCULATION AND NOT ALLOW FOR MUCH ADDITIONAL STRENGTHENING. THE
LATEST NHC INTENSITY FORECAST SHOWS SOME SLIGHT STRENGTHENING OVER
THE NEXT 12 H. MODELS ARE IN FAIRLY GOOD AGREEMENT THAT STEADY
WEAKENING WILL BEGIN FRIDAY, WITH THE SYSTEM BECOMING A DEPRESSION
ON FRIDAY NIGHT.
JOHN HAS A VERY LARGE RAIN SHIELD, AND FLOODING IMPACTS WILL EXTEND
WELL OUTSIDE WHERE THE SYSTEM MAKES LANDFALL. 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 AND MICHOACAN.
KEY MESSAGES:
1. HURRICANE 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 STRENGTHENING UP UNTIL LANDFALL, AND
A HURRICANE WARNING IS IN EFFECT ALONG THE COASTLINE OF SOUTHWESTERN
MEXICO, WHERE HURRICANE CONDITIONS ARE IMMINENT. TROPICAL STORM
WARNINGS ARE ALSO IN EFFECT FOR PORTIONS OF THE AREA, WHERE
TROPICAL STORM CONDITIONS ARE ONGOING OR IMMINENT.
FORECAST POSITIONS AND MAX WINDS
INIT 26/2100Z 17.6N 102.8W 65 KT 75 MPH
12H 27/0600Z 18.0N 103.0W 70 KT 80 MPH
24H 27/1800Z 18.6N 103.5W 40 KT 45 MPH...INLAND
36H 28/0600Z 19.2N 104.7W 30 KT 35 MPH...OVER WATER
48H 28/1800Z 19.8N 106.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 29/0600Z 20.6N 107.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 29/1800Z...DISSIPATED
FORECASTER KELLY
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