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Tropical Depression Norbert Forecast Discussion Number 9
2020-10-07 22:50:51| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Wed Oct 07 2020 000 WTPZ44 KNHC 072050 TCDEP4 Tropical Depression Norbert Discussion Number 9 NWS National Hurricane Center Miami FL EP192020 300 PM MDT Wed Oct 07 2020 Convection has decreased in association with Norbert since the last advisory, with the system now comprised of a mostly-exposed swirl of low-level clouds. Based on the weakened cloud pattern, the initial intensity is reduced to 30 kt and Norbert is downgraded to a depression. Daytime visible imagery shows that Norbert is south of the previous advisory location, and the initial motion is a somewhat uncertain 180/2. Little motion is expected during the next 12 h or so as the cyclone is in an area of weak steering currents. A west-southwestward drift is forecast from 12-36 h. This will be followed by a slow motion toward the west-northwest or northwest for the remainder of the forecast period as a mid-level ridge builds to the north and northeast of Norbert. The forecast guidance has shifted to the right at 96 and 120 h, so the new forecast track is shifted in that direction as well. Otherwise, the new forecast, which lies near the various consensus models, has only slight changes since the previous advisory. While Norbert is seemingly in a favorable environment of light vertical wind shear over warm water, none of the intensity guidance calls for significant strengthening. Indeed, the GFS and ECMWF models call for the system to dissipate before 120 h, possibly due to dry air intrusions. Given the favorable shear and sea surface temperatures, the official intensity forecast calls for the system to survive for 5 days with little change in strength in overall agreement with the intensity guidance. It should be noted that if any strong convective bursts occur, these could cause the system to strengthen just the little bit it needs to regain tropical storm strength. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 13.4N 107.1W 30 KT 35 MPH 12H 08/0600Z 13.4N 107.1W 30 KT 35 MPH 24H 08/1800Z 13.3N 107.4W 30 KT 35 MPH 36H 09/0600Z 13.1N 107.8W 30 KT 35 MPH 48H 09/1800Z 13.1N 108.2W 30 KT 35 MPH 60H 10/0600Z 13.8N 108.8W 30 KT 35 MPH 72H 10/1800Z 14.7N 109.6W 30 KT 35 MPH 96H 11/1800Z 16.5N 111.0W 30 KT 35 MPH 120H 12/1800Z 18.0N 112.5W 30 KT 35 MPH $$ Forecaster Beven
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