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ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM 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 hurricane to accelerate northeastward. The track guidance is in good agreement on the track of Sergio, although there is still some uncertainty associated with the timing for when Sergio will reach the west coast of the Baja California peninsula. Only minor changes were made to the official track forecast, which lies near the middle of the guidance envelope and very close to TVCN. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 15.3N 128.6W 80 KT 90 MPH 12H 09/0000Z 15.9N 128.4W 75 KT 85 MPH 24H 09/1200Z 16.6N 127.6W 70 KT 80 MPH 36H 10/0000Z 17.4N 126.1W 65 KT 75 MPH 48H 10/1200Z 18.6N 124.0W 65 KT 75 MPH 72H 11/1200Z 22.3N 119.0W 55 KT 65 MPH 96H 12/1200Z 27.5N 113.0W 40 KT 45 MPH...INLAND 120H 13/1200Z 33.0N 105.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Zelinsky NNNN