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Tropical Storm Norbert Discussion Number   5
NWS National Hurricane Center Miami FL       EP192020
300 PM MDT Tue Oct 06 2020
 
A compact central dense overcast with cloud tops occasionally
cooling to -80 degrees C has persisted over the center of Norbert
throughout the day. A recent ASCAT overpass showed peak winds of 41
kt near the center of storm. However, due to the small size of the
cyclone, the highest winds are likely not being sampled. Therefore,
the initial intensity is being raised to 45 kt, and this is in good
agreement with the latest Dvorak CI values from TAFB and SAB.

Norbert is expected to remain in an environment of low vertical wind 
shear while over very warm waters for the next couple of days.  
Despite the positive environmental factors in the near term, model 
guidance is in poor agreement on the future intensity of Norbert. 
The spread in the forecast intensity has widened even further today, 
with most of the global and hi-resolution dynamical models 
weakening the system over the next few days, while the SHIPS and 
LGEM guidance favor slow strengthening. Since the SHIPS guidance 
has been the most accurate for Norbert's intensity thus far, the 
latest NHC forecast is close to, but just below the SHIPS guidance 
values through 48 h. After 48 h, the shear is expected to become 
moderate, and there are indications that subsidence will increase 
over the cyclone. These negative environmental factors should 
inhibit further intensification, and could cause the cyclone to 
weaken.
 
The steering currents around Norbert are collapsing, as the 
mid-level ridge over southern Mexico dissipates in response to 
Hurricane Delta over the northwestern Caribbean Sea. Model tracks 
diverge by a few hundred miles in varying directions while the 
steering flow is weak. The consensus guidance is in between these 
solutions and shows very little movement for the next 72 h. By late 
this week, a weak mid-level ridge should build north of the cyclone, 
which would result in a slow west-northwestward to westward motion. 
The latest NHC track forecast remains close to the various consensus 
aids.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/2100Z 14.4N 106.6W   45 KT  50 MPH
 12H  07/0600Z 14.5N 106.7W   50 KT  60 MPH
 24H  07/1800Z 14.5N 106.7W   50 KT  60 MPH
 36H  08/0600Z 14.5N 106.7W   55 KT  65 MPH
 48H  08/1800Z 14.5N 106.7W   55 KT  65 MPH
 60H  09/0600Z 14.5N 107.2W   50 KT  60 MPH
 72H  09/1800Z 14.8N 108.0W   50 KT  60 MPH
 96H  10/1800Z 15.5N 110.1W   50 KT  60 MPH
120H  11/1800Z 16.0N 112.0W   50 KT  60 MPH
 
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Forecaster Latto
 
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