000 WTPZ41 KNHC 060232 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 do not appear to be any other negative factors that would significantly disrupt Sergio's intensity for the next 36-48 hours. By 72 hours and beyond, however, increasing southwesterly vertical wind shear is expected to induce a steady weakening trend after the cyclone begins accelerating toward the northeast, and on days 4 and 5 passing over the cold wake left behind by former Hurricane Rosa. The new official intensity forecast is similar to the previous one, and is near an average of the NOAA-HCCA and IVCN consensus models. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 15.3N 122.7W 110 KT 125 MPH 12H 06/1200Z 15.0N 123.6W 110 KT 125 MPH 24H 07/0000Z 14.7N 124.8W 105 KT 120 MPH 36H 07/1200Z 14.8N 125.8W 100 KT 115 MPH 48H 08/0000Z 15.4N 126.5W 95 KT 110 MPH 72H 09/0000Z 17.1N 126.0W 85 KT 100 MPH 96H 10/0000Z 19.4N 122.7W 70 KT 80 MPH 120H 11/0000Z 23.0N 118.0W 60 KT 70 MPH $$ Forecaster Stewart