721
WTNT41 KNHC 071455
TCDAT1

Hurricane Delta Discussion Number 12
NWS National Hurricane Center Miami FL AL262020
1000 AM CDT Wed Oct 07 2020

Satellite and surface observations show that Delta made landfall
along the northeastern coast of the Yucatan peninsula around 1030
UTC near Puerto Morelos. A WeatherFlow observing site at Puerto
Morelos reported near calm winds and a minimum pressure of around
972 mb when the center passed that location. Another WeatherFlow
site near Cancun reported peak sustained winds of 73 kt with a gust
to 92 kt. Hurricane-force winds gusts were also reported at an
observing site on Cozumel. Since landfall, Delta has moved across
the northeastern portion of the Yucatan peninsula and is now about
the emerge off the northern coast of the peninsula into the
southern Gulf of Mexico. Assuming some weakening has occurred, the
initial intensity has been set at 90 kt, but this could be a little
generous. An Air Force Reserve Hurricane Hunter aircraft is
scheduled to investigate Delta early this afternoon. A NOAA P-3
aircraft has been preforming a Tail Doppler Radar mission this
morning.

Once Delta moves over the southern Gulf of Mexico, warm waters and
expected low vertical wind shear conditions are expected to allow
for re-strengthening during the next 24 to 36 hours. After 48
hours, increasing southwesterly shear and cooler waters over the
northern Gulf are likely to induce some weakening. The intensity
guidance has trended downward this cycle, and the NHC forecast has
been adjusted accordingly. Delta, however is still expected to
regain major hurricane status and the wind field is likely to grow
in size during its approach to the northern Gulf coast, which will
increase the storm surge and wind threats. Regardless of Delta's
landfall intensity, life-threatening storm surge and strong winds
are likely over a large portion of the northwestern and northern
Gulf coast, which has necessitated the issuance of Storm Surge,
Hurricane, and Tropical Storm watches for portions of that area.

Delta is moving northwestward or 305/15 kt. The hurricane should
continue moving northwestward around the southwestern portion of a
subtropical ridge that extends over Florida and the northeastern
Gulf of Mexico through early Thursday. After that time, a
developing mid-level trough over the south-central United States
should cause Delta to slow down and turn north-northwestward on
Thursday. Delta is forecast to begin accelerating northward or north-northeastward toward the northern Gulf coast ahead of the
trough Thursday night and Friday. There has been little change to
the early portion of the track forecast, but there has been a little
westward shift in the guidance envelope after 24 hours, and the NHC
forecast has been moved in that direction. The new forecast track
lies near or just left of the TVCA multi-model consensus and a
little right of the HFIP corrected consensus aid, again close to the
GFS, GFS ensemble mean, and UKMet models.

Key Messages:

1. Life-threatening storm surge and dangerous winds will continue
within portions of the northern Yucatan Peninsula of Mexico into
early afternoon. Heavy rainfall, which could lead to significant
flash flooding, will affect the northern Yucatan Peninsula through
early Thursday.

2. Delta is expected to grow in size as it approaches the northern
Gulf Coast, where there is an increasing likelihood of life-
threatening storm surge and dangerous hurricane-force winds
beginning Friday, particularly for portions of the Louisiana coast.
Storm Surge and Hurricane Watches are in effect, and residents in
these areas should follow advice given by local officials.

3. Flash, urban, small stream, and minor river flooding is likely
Friday through Saturday from portions of the central Gulf Coast
northward into portions of the Lower to Middle Mississippi Valley.
As Delta moves farther inland, additional heavy rainfall is
expected in the Ohio Valley and Mid Atlantic this weekend.

FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 21.4N 88.0W 90 KT 105 MPH...INLAND
12H 08/0000Z 22.8N 90.2W 95 KT 110 MPH...OVER WATER
24H 08/1200Z 24.3N 92.4W 100 KT 115 MPH
36H 09/0000Z 26.0N 93.3W 105 KT 120 MPH
48H 09/1200Z 28.1N 93.3W 105 KT 120 MPH
60H 10/0000Z 30.8N 92.4W 70 KT 80 MPH...INLAND
72H 10/1200Z 33.2N 90.9W 40 KT 45 MPH...INLAND
96H 11/1200Z 36.5N 86.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 12/1200Z 39.5N 81.0W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown
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