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Tropical Storm Norbert Forecast Discussion Number 6
2020-10-07 04:38:35| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Tue Oct 06 2020 000 WTPZ44 KNHC 070238 TCDEP4 Tropical Storm Norbert Discussion Number 6 NWS National Hurricane Center Miami FL EP192020 900 PM MDT Tue Oct 06 2020 Norbert's satellite presentation has degraded slightly over the past several hours as its convective cloud tops have warmed compared to earlier today. The system may be feeling the effects of some weak westerly wind shear, as the coldest cloud tops are displaced somewhat to the east of the estimated low-level center position. Regardless, objective satellite estimates from UW-CIMSS and a T3.0 Dvorak classification from TAFB support holding the initial intensity at 45 kt with this advisory. Sea surface temperatures of 29 degrees Celsius and 10 kt or less of deep-layer vertical wind shear should support at least modest strengthening during the next 24 h or so. The latest SHIPS guidance indicates moderate southeasterly wind shear will develop over this small cyclone by Thursday and persist into the upcoming weekend. This should inhibit further intensification and may even cause Norbert to weaken. There is once again a fairly large spread in the intensity guidance, with the global models still struggling to capture this compact system and depicting steady weakening during the next few days. Meanwhile, SHIPS guidance maintains Norbert at tropical storm strength and even shows some gradual strengthening. Since the statistical-dynamical models have performed better with Norbert, the NHC intensity forecast once again trends above the consensus aids and closer to the SHIPS/LGEM guidance. The official forecast shows Norbert peaking as a 50-kt tropical storm on Wednesday, then weakening slightly on Thursday and leveling off through the weekend. Norbert is drifting slowly north-northwestward tonight. The storm is expected to remain nearly stationary over the next couple of days as distant Hurricane Delta over the northwestern Caribbean Sea weakens the mid-level ridge that had been steering Norbert. This weak steering environment could lead to some erratic storm motion until the ridge becomes re-established later this week, but the track guidance consensus suggests little movement during the next couple of days. By Friday night, the storm should begin moving slowly westward or west-northwestward, and the models are in better agreement with regards to this general storm motion at 72 h and beyond. The latest NHC track forecast follows the consensus aids more closely than any individual model solution. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 14.5N 106.9W 45 KT 50 MPH 12H 07/1200Z 14.6N 107.0W 50 KT 60 MPH 24H 08/0000Z 14.7N 107.0W 50 KT 60 MPH 36H 08/1200Z 14.7N 107.1W 50 KT 60 MPH 48H 09/0000Z 14.7N 107.3W 45 KT 50 MPH 60H 09/1200Z 14.8N 108.0W 45 KT 50 MPH 72H 10/0000Z 15.2N 108.9W 45 KT 50 MPH 96H 11/0000Z 16.0N 110.5W 45 KT 50 MPH 120H 12/0000Z 16.5N 112.5W 50 KT 60 MPH $$ Forecaster Reinhart/Berg
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