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Hurricane Sergio Forecast Discussion Number 11
2018-10-02 04:58:17| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Mon Oct 01 2018 797 WTPZ41 KNHC 020258 TCDEP1 Hurricane Sergio Discussion Number 11 NWS National Hurricane Center Miami FL EP212018 900 PM MDT Mon Oct 01 2018 A just-received GMI overpass indicates that Sergio has become better organized with formation of a well-defined eye and eyewall under a convective overcast with cloud tops to -85C. Satellite intensity estimates are in the 55-65 kt range, and based on the improved structure, the intensity will be set at the upper end of that range. Thus, Sergio is upgraded to a hurricane. The intensity forecast is low confidence. The better structure of Sergio is now conducive for rapid intensification. However, the large-scale models forecast northeasterly vertical shear to increase to 20-25 kt by 24 h, which should be strong enough to stop rapid development, although the guidance suggests at least slow strengthening during this time. The intensity forecast follows the guidance trend in calling for gradual strengthening, but there could be a 12-h or so burst of rapid intensification before the shear gets too strong. The shear should subside after about 36 h while Sergio is still over warm water, and the forecast shows the system becoming a major hurricane near the 72 h point in response to the more favorable conditions. After 72 h, a combination of decreasing sea-surface temperatures along the forecast track and entrainment of drier air should lead to gradual weakening. The initial motion is 265/12. As stated in the previous discussion, a westward motion at about the same forward speed is expected during the next day or so while the storm remains on the south side of a mid-level ridge. A turn to the west-northwest is forecast by late Tuesday, followed by a northwestward motion on Wednesday as the western portion of the mid-level ridge erodes due to a large scale mid- to upper-level trough near the southwestern United States. By the end of the forecast period, a ridge is expected to build to the north of Sergio, which should cause a turn back toward the west. The track guidance has changed little since the last advisory, and the new NHC track is close to both the previous forecast track and the consensus models. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 10.9N 112.0W 65 KT 75 MPH 12H 02/1200Z 11.2N 113.7W 75 KT 85 MPH 24H 03/0000Z 11.7N 115.6W 80 KT 90 MPH 36H 03/1200Z 12.6N 117.2W 85 KT 100 MPH 48H 04/0000Z 13.7N 118.5W 95 KT 110 MPH 72H 05/0000Z 16.0N 121.0W 100 KT 115 MPH 96H 06/0000Z 17.0N 124.0W 95 KT 110 MPH 120H 07/0000Z 17.5N 127.0W 85 KT 100 MPH $$ Forecaster Beven
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