WTPZ41 KNHC 050232 RRA

TCDEP1



HURRICANE SERGIO DISCUSSION NUMBER  23

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212018

800 PM PDT THU OCT 04 2018



SERGIO'S CLOUD PATTERN HAS DETERIORATED SOMEWHAT SINCE THE PREVIOUS

ADVISORY, WITH CLOUD TOPS WARMING AND THE EYE BECOMING MORE RAGGED

AND LESS DISTINCT. THE INITIAL INTENSITY IS REDUCED TO 110 KT BASED

ON A BLEND OF THE LATEST OBJECTIVE AND SUBJECTIVE DVORAK ESTIMATES.

SERGIO IS EXPECTED TO STEADILY WEAKEN FOR THE NEXT 48 HOURS WHILE

MOVING INTO A DRIER AND MORE STABLE ENVIRONMENT. BY THEN, MOST OF

THE GUIDANCE SUGGESTS LITTLE CHANGE FROM 48-72 HOURS BEFORE THE

SHEAR INCREASES BY THE END OF THE PERIOD AND SSTS COOL TO BETWEEN

26C AND 27C, WHICH SHOULD AGAIN RESULT IN WEAKENING. THE NEW NHC

INTENSITY FORECAST IS LOWER THAN THE PREVIOUS ONE DURING THE FIRST

48 HOURS TO ACCOUNT FOR THE OBSERVED WEAKENING AND THE TREND IN THE

GUIDANCE, BUT IS SIMILAR AFTER THAT TIME. THIS PREDICTION IS CLOSE

TO OR A BIT ABOVE THE LATEST HCCA INTENSITY CONSENSUS AID.



SERGIO HAS TURNED TOWARD THE LEFT DURING THE PAST FEW HOURS, WITH AN

INITIAL MOTION ESTIMATE NOW 305/07. A MID-LEVEL RIDGE BUILDING TO

THE NORTHWEST OF SERGIO WILL STEER THE HURRICANE TOWARD THE WEST AND

EVEN TOWARD THE WEST-SOUTHWEST DURING THE NEXT 36 TO 48 HOURS. AFTER

THAT TIME, AN AMPLIFYING LONGWAVE TROUGH OVER WESTERN NORTH AMERICA

WILL ERODE THE RIDGE AND CAUSE SERGIO TO RECURVE, WITH A FASTER

NORTHEASTWARD MOTION SHOWN BY DAY 5. THE NEW NHC TRACK FORECAST HAS

BEEN ADJUSTED TO THE SOUTH OF THE PREVIOUS ONE FROM 24 TO 48 HOURS,

FOLLOWING THE TREND OF THE LATEST CONSENSUS AIDS, WHICH ARE SHOWING

A MORE EQUATORWARD MOTION DURING THIS TIME. AT DAYS 3 THROUGH 5, THE