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Tropical Depression Norbert Discussion Number 11
NWS National Hurricane Center Miami FL EP192020
300 AM MDT Thu Oct 08 2020
Norbert was very close to becoming a remnant low overnight. A recent
burst of deep convection to the southeast of the partially exposed
low-level center was sufficient to keep Norbert as a tropical
depression for this advisory. Water vapor imagery indicates the
depression is still battling dry mid-level air on the northern
periphery of the circulation. The initial intensity has been lowered
to 25 kt based on a 04 UTC ASCAT-B overpass that showed max winds of
25 kt in the southwest quadrant of Norbert.
Norbert is presently drifting east-southeastward under weak
steering currents, and the cyclone may continue meandering
erratically for the next 6-12 h. Then, Norbert is forecast to move
slowly west-southwestward or westward through 48 h. Thereafter, a
mid-level ridge is expected to build to the north and northeast of
Norbert, which should steer the system northwestward at a slightly
faster speed. The NHC forecast track is shifted slightly to the
right of the previous one based on the guidance consensus aids
including TVCE and HCCA.
Although drier mid-level air continues to impinge on the northern
side of Norbert's circulation, the depression remains in an
otherwise favorable environment of high oceanic heat content and
light vertical wind shear. If Norbert can survive the slight
increase in deep-layer shear depicted by the SHIPS guidance during
the next 24 h, improving environmental conditions thereafter could
allow Norbert to at least remain a depression for several days.
Alternatively, moderate shear and additional dry air intrusions
could cause Norbert to degenerate into a remnant low at almost
any time. The NHC intensity forecast assumes the first scenario and
keeps Norbert as a 25-30 kt depression for the next several days. By
96-120 h, GFS simulated satellite imagery suggests the cyclone will
be devoid of convection as it moves into a drier mid-level
environment. Thus, the official forecast depicts a transition to
remnant low status by day 4.
FORECAST POSITIONS AND MAX WINDS
INIT 08/0900Z 13.2N 106.3W 25 KT 30 MPH
12H 08/1800Z 13.0N 106.2W 25 KT 30 MPH
24H 09/0600Z 13.0N 106.5W 25 KT 30 MPH
36H 09/1800Z 13.2N 107.0W 30 KT 35 MPH
48H 10/0600Z 13.5N 107.6W 30 KT 35 MPH
60H 10/1800Z 14.4N 108.2W 30 KT 35 MPH
72H 11/0600Z 15.3N 108.6W 30 KT 35 MPH
96H 12/0600Z 16.0N 109.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 13/0600Z 16.5N 110.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
$$
Forecaster Reinhart/Zelinsky
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