Tropical Storm Norbert Discussion Number 22
NWS National Hurricane Center Miami FL EP192020
300 AM MDT Wed Oct 14 2020
Norbert continues to produce a concentrated area of deep convection,
but it has been very difficult pinpointing the exact location of the
center overnight. Earlier ASCAT data and an 0152 UTC SSMIS
microwave overpass suggests that the center could be a little north
of the previous estimates, but overnight shortwave infrared imagery
and TAFB and SAB fixes still place it closer to the southern portion
of the convective mass. The advisory position is a compromise
between the various estimates, but leans toward the previous track
out of respect for continuity. Dvorak estimates from TAFB and SAB
support an intensity of 35 kt, which is used as the initial wind
speed for this advisory. The earlier ASCAT overpass revealed some
slightly stronger wind vectors, but these appear to have been rain
inflated.
The initial motion estimate is a somewhat uncertain 325/13 kt.
Norbert is moving northwestward between a mid-level ridge over
northern Mexico and a mid- to upper-level low to its northwest. This
general heading should continue over the next 24 to 36 hours with
some reduction in forward speed as Norbert begins to weaken and is
steered by the weaker low-level flow. The dynamical models are
in general agreement, but there are differences in how fast and far
north Norbert will move. The models that maintain a deeper cyclone
depict a more poleward motion. The NHC track leans toward the
southern solutions by 24 hours since Norbert is likely to weaken and
become a more vertically shallow system by that time.
Norbert only has a short window of opportunity in which to
strengthen this morning. After that time, increasing southwesterly
shear and cooler sea surface temperatures should begin to weaken
the tropical storm. Norbert is likely to become a remnant low in
24 to 36 hours as it encounters sea surface temperatures below 26C,
moderate to strong shear, and a more stable atmosphere. The global
models indicate that the low will dissipate within a couple of
days, and the NHC forecast follows suit.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0900Z 22.1N 113.3W 35 KT 40 MPH
12H 14/1800Z 23.5N 114.3W 35 KT 40 MPH
24H 15/0600Z 24.9N 115.2W 30 KT 35 MPH
36H 15/1800Z 26.0N 115.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 16/0600Z...DISSIPATED
$$
Forecaster Brown
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