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Hurricane Zeta Forecast Discussion


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000
WTNT43 KNHC 281449
TCDAT3

Hurricane Zeta Discussion Number  16
NWS National Hurricane Center Miami FL       AL282020
1000 AM CDT Wed Oct 28 2020

Zeta has a well-organized cloud pattern on satellite images, and the
eye has been fairly well-defined.  Strong upper-level outflow is
evident over the northern semicircle of the hurricane.  Reports from
Air Force and NOAA Hurricane Hunter aircraft indicate that the
system had continued to strengthen over the past few hours.  Peak
700-mb flight level winds were 89 kt, which equates to a maximum
surface wind of about 80 kt, and The central pressure has fallen to
976 mb.  Zeta still has a few hours to intensify before it begins to
move over the cooler waters of the northern Gulf of Mexico, and
southwesterly shear is likely to increase by the time the center
reaches the coast.  Even if a little weakening begins later today,
however, Zeta should maintain hurricane strength through landfall.
The official intensity forecast is near the high end of the model
guidance.  In 36 hours or so, the global models clearly depict the
system as a frontal wave approaching the United States east coast so
the official forecast shows an extratropical cyclone at that point
and beyond.  After 48 hours, the models show the low becoming
elongated and absorbed into the frontal zone.

The hurricane has turned northward and is now moving at around
010/16 kt.  A strong 500-mb trough moving into Texas will continue
to move eastward during the next 36-48 hours.  The flow ahead of
this trough will cause Zeta to accelerate north-northeastward and
move inland along the central Gulf Coast in 6-12 hours.  On
Thursday, the cyclone will then move northeastward on the east
side of the trough, at an even faster pace, over the southeastern
United States.  By early Friday, the system should move east-
northeastward in the westerlies and into the western Atlantic as an
extratropical cyclone.  The official track forecast is close to the
previous one and generally follows the dynamical model consensus.

Given Zeta's acceleration near and after landfall, strong winds are
likely to spread well inland over the southeastern U.S. this evening
and early Thursday.

KEY MESSAGES:

1. A life-threatening storm surge is expected along portions of the
northern Gulf Coast beginning later today, with the highest
inundation occurring between Port Fourchon, Louisiana, and Dauphin
Island, Alabama. Residents in the Storm Surge Warning area should
follow any advice given by local officials.  Overtopping of local,
non-federal levee systems is possible within southeastern Louisiana
outside of the Hurricane and Storm Damage Risk Reduction System.

2.  Hurricane conditions are expected this afternoon and evening
within portions of the Hurricane Warning area along the southeastern
Louisiana and Mississippi coasts.  Tropical storm conditions are
expected within portions of the Tropical Storm Warning area along
the Alabama and far western Florida Panhandle coasts.

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

4.  Through Thursday, heavy rainfall is expected from portions of
the central U.S. Gulf Coast into the Mid-Mississippi Valley, Ohio
Valley, southern to central Appalachians, and Mid-Atlantic States
near and in advance of Zeta. This rainfall will lead to flash,
urban, small stream, and minor river flooding.


FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 26.9N  91.7W   80 KT  90 MPH
 12H  29/0000Z 30.1N  89.9W   80 KT  90 MPH...INLAND
 24H  29/1200Z 35.3N  83.9W   40 KT  45 MPH...INLAND
 36H  30/0000Z 39.1N  74.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  30/1200Z 41.5N  63.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 60H  31/0000Z...DISSIPATED

$$
Forecaster Pasch