[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 290840
TCDAT3

Tropical Storm Zeta Discussion Number  19
NWS National Hurricane Center Miami FL       AL282020
400 AM CDT Thu Oct 29 2020

Surface observations and Doppler radar data indicate that Zeta
weakened to a tropical storm around 0600 UTC when it was located
over central Alabama.  During the past few hours, the cyclone's
structure has degraded further with the center no longer easily
apparent in radar images and convection appearing more ragged and
asymmetric.  The initial intensity is lowered to 50 kt for this
advisory, and that could be a little generous.  The minimum
pressure is estimated to be 988 mb based on surface observations.

The storm continues to accelerate, and the latest initial motion is
northeastward at 34 kt.  Zeta is expected to race northeastward
today in the fast steering flow between a potent mid- to upper-level
low to its west and a high pressure ridge to its southeast.  This
pattern should take the cyclone across the southeast and
Mid-Atlantic states throughout the day, before emerging over the
western Atlantic this evening.  An even faster east-northeastward
motion is predicted tonight and on Friday until the cyclone
dissipates by Friday night.

The tropical storm is forecast to weaken a little more during the
next several hours as it remains over land, and Zeta will likely
become extratropical by the time it reaches the mid-Atlantic
states this afternoon.  However, after that time, the models show
the cyclone leveling off in strength or perhaps even
re-intensifying over the western Atlantic before it becomes
absorbed into a frontal zone in 36 to 48 hours.  The NHC intensity
forecast follows the GFS and ECMWF models.


KEY MESSAGES:

1.  Strong, damaging wind gusts, which could cause tree damage and
power outages, will continue to spread well inland across portions
of northeastern Alabama, northern Georgia, the Carolinas, and
southeastern Virginia today due to Zeta's fast forward speed.  Wind
gusts could be especially severe across the southern Appalachian
Mountains.

2.  Through today, heavy rainfall is expected near and in advance of
Zeta from portions of the central Appalachians, Mid-Atlantic and
lower to middle Ohio Valley. This rainfall may lead to flash, urban,
small stream, and isolated minor river flooding.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 34.0N  85.5W   50 KT  60 MPH...INLAND
 12H  29/1800Z 37.7N  79.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
 24H  30/0600Z 40.8N  66.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  30/1800Z 43.4N  54.6W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  31/0600Z...DISSIPATED

$$
Forecaster Cangialosi
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