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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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