WTPZ41 KNHC 081448 RRA

TCDEP1



HURRICANE SERGIO DISCUSSION NUMBER  37

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212018

800 AM PDT MON OCT 08 2018



SERGIO'S STRUCTURE HAS REMAINED NEARLY STEADY-STATE FOR THE PAST 24

HOURS.  A SOLID RING OF DEEP CONVECTION SURROUNDS SERGIO'S GIANT

EYE, AND THERE IS LITTLE EVIDENCE OF ANY CONVECTIVE BANDS.  DESPITE

UPWELLING THAT IS PRESUMABLY OCCURING BENEATH THE SLOW MOVING

HURRICANE, CLOUD TOPS HAVE ACTUALLY COOLED OVER THE PAST FEW HOURS,

AND SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB HAVE NOT

CHANGED. THE INITIAL INTENSITY HAS THEREFORE BEEN HELD AT 80 KT,

WHICH ALSO AGREES WITH A 1045 UTC UW-CIMSS SATCON ESTIMATE.



AS LONG AS SERGIO CAN MAINTAIN ITS ANNULAR STRUCTURE IN AN

ENVIRONMENT OF NEGLIGIBLE SHEAR, ONLY VERY GRADUAL WEAKENING IS

EXPECTED, DESPITE PRESUMABLY COOLING WATERS BENEATH THE CYCLONE

ASSOCIATED WITH ITS SLOW MOVEMENT.  THE ECMWF AND GFS FORECAST THAT

THE SHEAR WILL BEGIN TO INCREASE IN ABOUT 24 TO 36 HOURS, AND THE

CYCLONE WILL ALSO BE REACHING MUCH COOLER WATERS SHORTLY AFTER THAT

TIME.  A FASTER RATE OF WEAKENING IS THEREFORE ANTICIPATED BEYOND

48 H, IN LINE WITH THE LATEST INTENSITY CONSENSUS, AND SERGIO IS

FORECAST TO BE A TROPICAL STORM WHEN IT APPROACHES NORTHWESTERN

MEXICO IN A FEW DAYS.  THE CYCLONE SHOULD WEAKEN QUICKLY AFTER

LANDFALL, AND WILL LIKELY DISSIPATE OVER THE HIGH TERRAIN OF

MAINLAND MEXICO, THOUGH A 5 DAY REMNANT LOW POINT IS STILL SHOWN

FOR CONTINUITY PURPOSES.



SERGIO IS MOVING VERY LITTLE RIGHT NOW, AND THE SLOW MOTION WILL

LIKELY CONTINUE DURING THE DAY TODAY.  BY TONIGHT, A LARGE TROUGH

CENTERED OVER THE SOUTHWESTERN UNITED STATES WILL CAUSE THE