WTPZ41 KNHC 060232 RRA

TCDEP1



HURRICANE SERGIO DISCUSSION NUMBER  27

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212018

800 PM PDT FRI OCT 05 2018



SERGIO HAS MAINTAINED A 25-30-NMI WIDE EYE THIS EVENING, AND A RING

OF COLD CLOUD TOPS HAS COOLED AROUND THE WELL-DEFINED EYE. SATELLITE

INTENSITY ESTIMATES RANGE FROM T5.5/102 KT FROM TAFB AND SAB TO

T5.9/122 KT FROM ADT AND A T6.0/115 KT NHC OBJECTIVE T-NUMBER, SO

THE INTENSITY HAS BEEN BUMPED UP TO 110 KT FOR THIS ADVISORY.

UPPER-LEVEL OUTFLOW AND THE OVERALL CONVECTIVE PATTERN HAVE BOTH

IMPROVED SINCE THE PREVIOUS ADVISORY WHILE SERGIO HAS LOST LATITUDE

AND MOVED OVER WARMER WATERS.



THE MOTION IS NOW SOUTHWESTWARD, OR 235/06 KT. SERGIO'S RECENT

SOUTHWESTWARD MOTION IS FORECAST TO BE SHORT LIVED, WITH A RETURN TO

A WEST-SOUTHWESTWARD TO WESTWARD MOTION EXPECTED WITHIN THE NEXT 12

HOURS. THE DEEP-LAYER RIDGE TO THE NORTH OF SERGIO IS FORECAST TO

BECOME MORE NARROW DUE TO A PASSING SHORTWAVE TROUGH, BUT IT IS

BASICALLY EXPECTED TO REMAIN INTACT. THIS FEATURE WILL STEER THE

HURRICANE SLOWLY WESTWARD THROUGH SUNDAY. BY MONDAY, HOWEVER, A

STRONGER TROUGH IS FORECAST BY THE GLOBAL MODELS TO DROP SOUTHWARD

OFF THE COASTS OF CALIFORNIA AND BAJA CALIFORNIA, CAUSING A

SIGNIFICANT WEAKENING AND EROSION OF THE WESTERN PORTION OF THE

RIDGE. THIS IS EXPECTED TO RESULT IN SERGIO TURNING SLOWLY

NORTHEASTWARD ON MONDAY, AND ACCELERATE ON DAYS 4 AND 5. THE NEW NHC

FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK, AND LIES

CLOSE TO CONSENSUS MODELS TVCE AND NOAA-HCCA.



OTHER THAN VERY BRIEF INTRUSIONS OF DRY MID-LEVEL AIR AND POSSIBLE

UPWELLING BENEATH THE HURRICANE DUE TO ITS SLOW FORWARD SPEED, THERE