WTPZ42 KNHC 070831 RRA

TCDEP2



HURRICANE JOHN DISCUSSION NUMBER   7

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122018

300 AM MDT TUE AUG 07 2018



SATELLITE IMAGES INDICATE THAT JOHN HAS RESUMED ITS INTENSIFICATION

TREND, WITH A RAGGED EYE SHOWING UP IN THE NIGHT-VISIBLE AND OTHER

CHANNELS.  DVORAK ESTIMATES ARE BETWEEN 70-90 KT, SO 80 KT IS USED

AS THE INITIAL WIND SPEED.  JOHN HAS ANOTHER DAY OR SO TO INTENSIFY

IN A LOW-SHEAR, WARM-WATER ENVIRONMENT BEFORE IT RAPIDLY CROSSES

INTO COOLER WATERS.  THE HURRICANE HAS BEEN INTENSIFYING AT A RATE

OF ABOUT 30 KT/24 HOURS, SO THIS TREND WAS HEAVILY WEIGHTED IN THE

LATEST FORECAST GIVEN THE CONTINUATION OF THE CONDUCIVE ENVIRONMENT.

ALL OF THE GUIDANCE SHOW A PRETTY STEEP DROP IN INTENSITY AS THE

HURRICANE QUICKLY ENTERS COOL WATERS, WITH RAPID WEAKENING LIKELY.

THE LATEST FORECAST IS CLOSE TO THE PREVIOUS ONE, BUT SHOWS JOHN

BECOMING POST-TROPICAL BY DAY 4 WHEN IT WILL BE OVER 21C WATERS.



JOHN CONTINUES TO MOVE NORTHWESTWARD, NOW AT ABOUT 8 KT.  THE

HURRICANE SHOULD MOVE IN THAT GENERAL DIRECTION BUT FASTER OVER THE

NEXT 3 DAYS UNDER THE INFLUENCE OF A STRENGTHENING SUBTROPICAL

RIDGE.  AS JOHN WEAKENS, THE CYCLONE IS FORECAST TO TURN WESTWARD,

STEERED MORE BY THE LOW-LEVEL RIDGE.  GUIDANCE REMAINS TIGHTLY

CLUSTERED AND NO SIGNIFICANT CHANGE WAS MADE TO THE PREVIOUS

FORECAST TRACK.



THE DANGEROUS CORE OF JOHN IS FORECAST TO REMAIN WELL OFFSHORE OF

THE BAJA CALIFORNIA PENINSULA.  HOWEVER, AN EASTWARD SHIFT OF THE

FORECAST TRACK OR AN UNEXPECTED INCREASE IN THE SIZE OF THE OUTER

WIND FIELD OF THE HURRICANE COULD BRING TROPICAL-STORM-FORCE WINDS

TO PORTIONS OF THE WEST COAST OF THE PENINSULA. THEREFORE, INTERESTS