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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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