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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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