WTPZ45 KNHC 292042 RRA

TCDEP5



HURRICANE ROSA DISCUSSION NUMBER  19

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202018

200 PM PDT SAT SEP 29 2018



THE STRENGTHENING TREND SEEN EARLIER HAS AT LEAST SLOWED, AS ROSA

HAS SHOWN LITTLE CHANGE IN ORGANIZATION SINCE THE LAST ADVISORY.

THE HURRICANE CONTINUES TO HAVE A WELL-DEFINED 30-40 N MI WIDE EYE

INSIDE A CENTRAL DENSE OVERCAST WITH CLOUD TOPS AS COLD AS -75C.

THE VARIOUS SATELLITE INTENSITY ESTIMATES HAVE CHANGED LITTLE, SO

THE INITIAL INTENSITY REMAINS 90 KT.  THE HURRICANE HAS GOOD TO

EXCELLENT CIRRUS OUTFLOW IN THE NORTHEASTERN SEMICIRCLE, AND THE

OUTFLOW HAS RECENTLY IMPROVED IN THE SOUTHWESTERN SEMICIRCLE.



ROSA IS NOW CROSSING THE 26C ISOTHERM, SO ADDITIONAL SIGNIFICANT

STRENGTHENING APPEARS UNLIKELY.  AFTER 12 H, THE COMBINATION OF

DECREASING SEA SURFACE TEMPERATURES AND INCREASING SHEAR SHOULD

CAUSE STEADY TO RAPID WEAKENING, AND THE INTENSITY FORECAST

CONTINUES TO CALL FOR THE CYCLONE TO WEAKEN BELOW HURRICANE STRENGTH

BEFORE THE CENTER REACHES THE BAJA CALIFORNIA PENINSULA IN JUST

OVER 48 H.  AFTER LANDFALL, THE SURFACE CIRCULATION IS FORECAST TO

DISSIPATE NEAR THE 72-H POINT IN AGREEMENT WITH ALL OF THE DYNAMICAL

MODELS.  HOWEVER, THE MID-LEVEL CIRCULATION AND THE ASSOCIATED

RAINFALL WILL CONTINUE MOVING ACROSS THE SOUTHWESTERN UNITED STATES

AFTER THE SURFACE CIRCULATION DISSIPATES.



THE INITIAL MOTION IS 350/10.  DURING THE FORECAST PERIOD, THE

HURRICANE WILL RECURVE INTO THE WESTERLIES BETWEEN A DEEP-LAYER

RIDGE OVER NORTHERN MEXICO AND A LARGE MID- TO UPPER-LEVEL TROUGH

OVER CALIFORNIA AND THE ADJACENT PACIFIC.  THIS SHOULD RESULT IN A

CONTINUED NORTHWARD MOTION THROUGH TONIGHT, FOLLOWED BY A TURN