WTPZ41 KNHC 010854 RRA

TCDEP1



TROPICAL STORM SERGIO DISCUSSION NUMBER   8

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212018

300 AM MDT MON OCT 01 2018



SERGIO'S CONVECTIVE PATTERN IN INFRARED SATELLITE IMAGERY HAS WAXED

AND WANED SINCE THE PREVIOUS ADVISORY. A PREVIOUSLY LARGE, SOLID

CURVED BAND HAS BECOME BROKEN DURING THE PAST COUPLE OF HOURS, BUT

THE COMMA HEAD OR CDO OF THE CLOUD BAND HAS INCREASED IN SIZE WHILE

CLOUD TOPS HAVE COOLED TO NEAR -80C. PASSIVE MICROWAVE IMAGERY

INDICATES THAT WITHIN THE COMMA HEAD FEATURE AN 18-20-NMI-WIDE

CLOSED EYE HAS DEVELOPED IN THE LOW-LEVELS, WHILE THE MID- AND

UPPER-LEVEL EYE REMAINS OPEN AND RAGGED. SUBJECTIVE INTENSITY

ESTIMATES REMAIN T3.5/55 KT FROM TAFB AND SAB. HOWEVER, BASED ON THE

WELL-DEFINED, LOW-LEVEL EYE, THE INTENSITY HAS BEEN NUDGED UPWARD TO

60 KT FOR THIS ADVISORY.



THE INITIAL MOTION IS NOW 270/12 KT, BASED PRIMARILY ON MICROWAVE

SATELLITE FIX POSITIONS. SERGIO IS FORECAST TO MOVE GENERALLY

WESTWARD FOR THE NEXT 36 HOURS OR SO, UNDER THE INFLUENCE OF A

STRONG, DEEP-LAYER RIDGE LOCATED TO THE NORTH OF THE CYCLONE. BY 48

HOURS, A MID- TO UPPER-LEVEL TROUGH MOVING SOUTHEASTWARD ALONG AND

OFFSHORE OF THE WESTERN U.S. IS EXPECTED TO GRADUALLY ERODE THE

WESTERN PART OF THE RIDGE, ALLOWING SERGIO TURN WEST-NORTHWESTWARD

ON DAY 2 AND MOVE NORTHWESTWARD ON DAYS 3-5.  THE NEW NHC TRACK

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

BLEND OF THE CONSENSUS MODELS TCVA, TVCE, AND HCCA.



BOTH THE STATISTICAL AND DYNAMICAL INTENSITY MODELS HAVE BEEN TOO

BULLISH ON SERGIO STRENGTHENING DURING THE PAST 36 HOURS. ALTHOUGH

THE ENVIRONMENT IS QUITE MOIST WITH NEAR 80 PERCENT MID-LEVEL