167
WTNT41 KNHC 082100
TCDAT1

Hurricane Delta Discussion Number 17
NWS National Hurricane Center Miami FL AL262020
400 PM CDT Thu Oct 08 2020

Delta is strengthening. In satellite imagery, an eye is now seen in
the cold cloud tops of the central dense overcast. On the aircraft
side, just received reports from an Air Force Reserve Hurricane
Hunter aircraft included 700-mb flight-level winds of 119 kt, SFMR
winds estimates near 90 kt, and a central pressure of 959 mb inside
a 30 n mi wide eye. A blend of the flight-level and SFMR wind
estimates give an initial intensity of 100 kt, and Delta is again a
major hurricane.

The initial motion is now northwestward or 320/10 kt. There is no
change to the track forecast philosophy and little change to the
track forecast from the previous advisory. During the next 12-24 h,
Delta should turn to the north between a mid- to upper-level ridge
over the Florida Peninsula and eastern Gulf of Mexico and a mid- to
upper-level level trough over the U.S. Southern Plains. This should
be followed by a north-northeastward motion that is expected to
bring the center near or over the northern Gulf coast, most likely
in southwestern Louisiana, in about 30 h. After landfall, the
cyclone should move northeastward through the Lower Mississippi and
Tennessee Valleys along the southern edge of the mid-latitude
westerlies until it dissipates. The track guidance remains very
tightly clustered in terms of direction, and the new forecast track
is near the various consensus models.

Shear, sea surface temperature, and moisture conditions appear
favorable for strengthening during the next 12 h or so, and based on
this additional intensification is expected tonight. A short period
of rapid intensification remains possible given current trends,
although the various rapid intensification indices are not
enthusiastic about the possibilities of this, After 12 h, the
global models again forecast strong southwesterly shear developing
over the hurricane before landfall, and based on this some weakening
is forecast. Rapid weakening is expected after landfall. The
system is expected to weaken to a depression no later than 60 h and
degenerate to a remnant low by 72 h, with dissipation following
shortly thereafter. The intensity forecast lies at or above the
upper edge of the intensity guidance.

Recent scatterometer data indicates that Delta is growing in size
as it approaches the Louisiana coast. The NHC wind radii forecast
again follows a combination of the data and the forecasts from
global and hurricane regional models.

Key Messages:

1. Life-threatening storm surge is expected near and east of where
Delta makes landfall Friday, 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 expected to grow in size.

2. Hurricane-force winds are expected Friday 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
Deltas center Friday evening and Friday night.

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

FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 24.8N 93.4W 100 KT 115 MPH
12H 09/0600Z 26.3N 93.9W 110 KT 125 MPH
24H 09/1800Z 28.6N 93.5W 105 KT 120 MPH
36H 10/0600Z 31.0N 92.5W 65 KT 75 MPH...INLAND
48H 10/1800Z 32.9N 91.1W 40 KT 45 MPH...INLAND
60H 11/0600Z 34.3N 89.2W 30 KT 35 MPH...INLAND
72H 11/1800Z 35.8N 87.2W 20 KT 25 MPH...POST-TROP/INLAND
96H 12/1800Z...DISSIPATED

$$
Forecaster Beven
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