[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 090845
TCDAT1

Hurricane Delta Discussion Number  19
NWS National Hurricane Center Miami FL       AL262020
400 AM CDT Fri Oct 09 2020

Delta has been generally steady in strength during the past several
hours as it starts to close in on the southwestern Louisiana coast.
An eye has occasionally been evident in geostationary satellite
images, and deep convection remains quite intense around that
feature.  The Air Force Hurricane Hunters recently found have been
investigating Delta this morning, and recently reported maximum
flight-level winds of 125 kt and peak SFMR surface winds of 99 kt.
Based on a blend of this data, the initial intensity is held at
105 kt. The hurricane appears to be leveling off in strength as
recent microwave passes show some asymmetry in the eyewall and
vertical tilt due to southwesterly shear.  The core of the hurricane
passed very close to NOAA buoy 42002 a few hours ago, and the
pressure at the buoy fell to 953 mb.  The buoy also reported peak
winds around 70 kt and a significant wave height of about 35 ft.

The major hurricane is now moving northward at 10 kt.  The track
forecast models remain quite consistent.  Delta is forecast to
continue moving northward today and then turn north-northeastward
tonight between a ridge over the western Atlantic and a trough over
the south-central United States.  This motion is expected to take
the core of the hurricane to the Louisiana coast this evening.
After landfall, a turn to the northeast is forecast as a larger
trough moves eastward toward Delta, and that motion should continue
until the cyclone dissipates over Tennessee or Kentucky in a few
days.  The models remain tightly clustered, and only minor tweaks
were made to the previous NHC track forecast.

Delta is expected to move over waters with progressively lower
oceanic heat content as it approaches the Louisiana coast.  These
less favorable oceanic conditions combined with an increase in
southwesterly shear should cause Delta to weaken a little before
it moves onshore.  Regardless, Delta is forecast to be near major
hurricane intensity when it makes landfall and significant impacts
are expected (see Key Messages below).  After landfall, rapid
weakening is anticipated and Delta is forecast to fall below
hurricane strength tonight or early Saturday and dissipate in about
3 days.

Key Messages:

1. Life-threatening storm surge is expected near and east of where
Delta makes landfall this evening, and a Storm Surge Warning is in
effect from High Island, Texas, to Ocean Springs, Mississippi. The
highest inundation of 7 to 11 feet is expected somewhere between
Rockefeller Wildlife Refuge and Morgan City, Louisiana. Residents
in the warning area should promptly follow advice given by local
officials. The storm surge risk remains high despite the forecast
decrease in intensity before landfall since Delta is a relatively
large hurricane.

2. Hurricane-force winds are expected this afternoon and evening
somewhere within the Hurricane Warning area between High Island,
Texas, and Morgan City, Louisiana.  Hurricane force winds will also
spread inland across portions of southern Louisiana near the path of
Delta’s center this evening and tonight.

3. Heavy rainfall will lead to significant flash flooding and minor
to major river flooding in parts of Louisiana today and Saturday.
Additional flooding is expected across portions of the central Gulf
Coast into the Lower Mississippi Valley.


FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 26.9N  93.7W  105 KT 120 MPH
 12H  09/1800Z 28.6N  93.3W   95 KT 110 MPH
 24H  10/0600Z 31.1N  92.3W   60 KT  70 MPH...INLAND
 36H  10/1800Z 32.9N  91.0W   30 KT  35 MPH...INLAND
 48H  11/0600Z 34.2N  89.1W   25 KT  30 MPH...INLAND
 60H  11/1800Z 35.6N  87.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  12/0600Z...DISSIPATED

$$
Forecaster Cangialosi

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