WTPZ45 KNHC 290840 RRA

TCDEP5



HURRICANE ROSA DISCUSSION NUMBER  17

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202018

200 AM PDT SAT SEP 29 2018



ROSA'S SATELLITE APPEARANCE HAS DEGRADED SIGNIFICANTLY SINCE THE

PREVIOUS ADVISORY WITH AN EYE NO LONGER EVIDENT IN INFRARED IMAGERY.

HOWEVER, A WELL-DEFINED LOW-LEVEL EYE IS EVIDENT IN RECENT PASSIVE

MICROWAVE IMAGERY. A COMPARISON OF THE TWO DATA SOURCES INDICATE

THAT THE UPPER-LEVEL CIRCULATION IS TILTED TO THE EAST OF THE

LOW-LEVEL EYE BY 12-18 NMI DUE TO WESTERLY SHEAR OF ABOUT 15 KT AS

ASSESSED BY UW-CIMSS. THE INITIAL INTENSITY OF 85 KT IS BASED ON A

BLEND OF SATELLITE INTENSITY ESTIMATES FORM TAFB, SAB, AND UW-CIMSS

ADT AND SATCON.



ROSA IS MOVING NORTHWARD NOW AND THE INITIAL MOTION ESTIMATE IS

350/08 KT. DURING THE NEXT 72 HOURS, THE HURRICANE IS FORECAST TO

MOVE AROUND THE WESTERN PERIPHERY OF A DEEP-LAYER RIDGE THAT EXTENDS

FROM THE GULF OF MEXICO WESTWARD TO BAJA CALIFORNIA, RESULTING IN A

NORTHWARD MOTION TODAY, AND A TURN TOWARD THE NORTH-NORTHEAST AT A

FASTER FORWARD SPEED ON MONDAY AND TUESDAY AS A MID-LATITUDE TROUGH

APPROACHES FROM THE WEST. THE LATEST NHC MODEL GUIDANCE IS TIGHTLY

PACKED ABOUT THE PREVIOUS FORECAST TRACK, SO NO SIGNIFICANT CHANGES

WERE REQUIRED. THE NEW NHC TRACK FORECAST LIES CLOSE TO A BLEND OF

THE CONSENSUS MODELS HCCA, FSSE, AND IVCN.



ROSA'S INTENSITY HAS DECREASED 40 KT DURING THE PAST 24 HOURS, WITH

THE BULK OF THE WEAKENING HAVING OCCURRED DURING THE PAST 18 HOURS,

AND ADDITIONAL WEAKENING IS EXPECTED DUE TO THE CYCLONE MOVING OVER

COOLER WATER AND INTO A REGIME OF INCREASING SOUTHWESTERLY VERTICAL

WIND SHEAR OF MORE THAN 30 KT BY 48 HOURS. ALTHOUGH ROSA IS