WTPZ42 KNHC 072035 RRA

TCDEP2



HURRICANE JOHN DISCUSSION NUMBER   9

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122018

300 PM MDT TUE AUG 07 2018



THE EYE OF JOHN HAS BECOME MORE DISTINCT IN VISIBLE AND INFRARED

SATELLITE IMAGERY DURING THE PAST FEW HOURS, HOWEVER THE SURROUNDING

CONVECTIVE CLOUDS TOPS HAVE WARMED, AND A 1642 UTC AMSU

MICROWAVE OVERPASS INDICATED THAT THE EYEWALL WAS OPEN OVER THE

NORTHWESTERN PORTION OF THE CIRCULATION.  ALTHOUGH OBJECTIVE DVORAK

T-NUMBERS HAVE INCREASED TO T5.6, SUBJECTIVE ESTIMATES FROM TAFB AND

SAB ARE UNCHANGED SO THE INITIAL INTENSITY IS KEPT AT 90 KT.  THERE

IS STILL AN OPPORTUNITY FOR JOHN TO BECOME A MAJOR HURRICANE TONIGHT

OR EARLY WEDNESDAY WHILE IT REMAINS OVER WARM WATER AND IN A LOW

SHEAR ENVIRONMENT.  AFTER THAT TIME, THE HURRICANE WILL BE MOVING

OVER DECREASING SSTS AND INTO A LESS FAVORABLE THERMODYNAMIC

ENVIRONMENT. THESE CONDITIONS SHOULD RESULT IN STEADY TO RAPID

WEAKENING AND JOHN IS FORECAST TO BECOME A POST-TROPICAL CYCLONE BY

DAY 4 WHEN IT IS OVER SSTS OF 20-21C.  THERE IS SIGNIFICANT SPREAD

IN THE INTENSITY GUIDANCE AS TO HOW RAPID JOHN WILL SPIN DOWN.  THE

NHC FORECAST IS A LITTLE HIGHER THAN THE ICON CONSENSUS MODEL, BUT

SHOWS A FASTER RATE OF WEAKENING THAN THE STATISTICAL GUIDANCE.



JOHN IS MOVING NORTHWESTWARD OR 320/9 KT.  THE HURRICANE SHOULD

CONTINUE MOVING NORTHWESTWARD AROUND THE WESTERN SIDE OF A

MID-LEVEL RIDGE OVER NORTHERN MEXICO DURING THE NEXT 2-3 DAYS.

AFTER THAT TIME, THE SYSTEM SHOULD TURN WESTWARD AS IT WEAKENS AND

COMES UNDER THE INFLUENCE OF THE LOW-LEVEL FLOW.  THE TRACK

GUIDANCE REMAINS IN EXCELLENT AGREEMENT AND THE NEW NHC TRACK IS