WTPZ42 KNHC 070848 RRA

TCDEP2



HURRICANE OLIVIA DISCUSSION NUMBER  27

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172018

200 AM PDT FRI SEP 07 2018



OLIVIA'S OVERALL CLOUD STRUCTURE IN INFRARED AND PASSIVE MICROWAVE

SATELLITE IMAGERY HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY,

EXCEPT THAT THE CLOUD TOPS HAVE WARMED SIGNIFICANTLY AROUND THE

WELL-DEFINED, 20-NMI-DIAMETER EYE. AS A RESULT, BOTH SUBJECTIVE AND

OBJECTIVE INTENSITY ESTIMATES HAVE DECREASED MARKEDLY SINCE OLIVIA

BRIEFLY REGAINED CATEGORY-4 STRENGTH ON THE PREVIOUS ADVISORY.

HOWEVER, MICROWAVE IMAGERY INDICATES THAT OLIVIA HAS EVOLVED INTO AN

ANNULAR HURRICANE, WITH ONLY INNER-CORE CONVECTION PRESENT AND NO

BANDING FEATURES. AS A RESULT, THE INITIAL INTENSITY ONLY BEEN

DECREASED TO 110 KT, WHICH IS A TYPICAL SLOWER RATE OF WEAKENING FOR

ANNULAR HURRICANES.



THE INITIAL MOTION ESTIMATE IS 290/13 KT. THERE IS NO SIGNIFICANT

CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. OLIVIA IS

EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD FOR THE NEXT 24-36

HOURS, FOLLOWED BY A WESTWARD MOTION AS THE HURRICANE NUDGES UP

AGAINST A STRONG DEEP-LAYER SUBTROPICAL RIDGE THAT STRETCHES FROM

MEXICO AND THE SOUTHWESTERN U.S. WESTWARD INTO THE CENTRAL PACIFIC.

THE NEW NHC FORECAST TRACK IS ESSENTIALLY JUST AN EXTENSION OF THE

PREVIOUS ADVISORY TRACK AND IS DOWN THE MIDDLE OF THE VERY TIGHTLY

PACKED MODEL GUIDANCE, CLOSEST TO THE SPEED OF THE TVCN CONSENSUS

TRACK MODEL.



AS MENTIONED IN THE PREVIOUS ADVISORY DISCUSSION, THE CURRENT

ANNULAR PATTERN INDICATES THAT HURRICANE OLIVIA SHOULD WEAKEN MORE

SLOWLY THAN INDICATED BY GUIDANCE, EVEN THOUGH THE CYCLONE WILL BE