WTPZ42 KNHC 091432 RRA

TCDEP2



TROPICAL STORM JOHN DISCUSSION NUMBER  16

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122018

800 AM PDT THU AUG 09 2018



JOHN'S STRUCTURE HASN'T CHANGED MUCH OVER THE PAST FEW HOURS. A

COMBINATION OF COOL SSTS AND STABLE AIR APPEAR TO BE CAUSING

CONVECTION TO ERODE IN THE SOUTHERN PORTION OF THE CYCLONE'S

CIRCULATION.  A BLEND OF OBJECTIVE AND SUBJECTIVE DVORAK

CLASSIFICATIONS WAS USED TO DETERMINE THE INITIAL INTENSITY OF 60

KT. THE TROPICAL STORM WILL BE MOVING OVER PROGRESSIVELY COOLER SSTS

FOR THE NEXT COUPLE OF DAYS, AND FURTHER WEAKENING IS INEVITABLE.

THE INTENSITY MODELS ARE IN GOOD AGREEMENT ON THE FORECAST WEAKENING

RATE, AND JOHN IS STILL FORECAST TO BECOME A REMNANT LOW WITHIN THE

NEXT 48 H.



THE INITIAL MOTION CONTINUES NEAR 305/14 KT.  THERE IS NO CHANGE TO

THE REASONING BEHIND THE TRACK FORECAST, AND THE NEW NHC FORECAST IS

MERELY AN UPDATE OF THE PREVIOUS ADVISORY.  ALL OF THE GUIDANCE

REMAINS IN GOOD AGREEMENT THAT THE CYCLONE SHOULD WILL GRADUALLY

TURN WEST-NORTHWESTWARD AS IT MOVES AROUND A MID-LEVEL RIDGE

CENTERED OVER THE SOUTHWESTERN U.S. FOR THE NEXT FEW DAYS. BY THE

END OF THE FORECAST PERIOD, THE REMNANT LOW IS LIKELY TO SLOW DOWN

TO A DRIFT WITHIN AN AREA OF WEAK LOW-LEVEL STEERING FLOW.



LARGE SWELLS ASSOCIATED WITH JOHN ARE ALREADY AFFECTING PORTIONS OF

THE COAST OF THE BAJA CALIFORNIA PENINSULA AND ARE FORECAST TO

SPREAD NORTHWARD AND REACH PORTIONS OF THE SOUTHERN CALIFORNIA COAST

BY TONIGHT. THESE SWELLS ARE LIKELY TO CAUSE LIFE- THREATENING SURF

AND RIP CURRENT CONDITIONS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL

WEATHER OFFICE.



FORECAST POSITIONS AND MAX WINDS