re: Delta Moves On...Cleanup Begins

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663
WTNT41 KNHC 072048
TCDAT1

Hurricane Delta Discussion Number 13
NWS National Hurricane Center Miami FL AL262020
400 PM CDT Wed Oct 07 2020

The center of Delta has moved off the northern coast of the Yucatan
peninsula and is now located over the southern Gulf of Mexico. The
hurricane remains well organized in satellite imagery with a large
curved band wrapping around the center and a fairly symmetric CDO.
An Air Force Reserve reconnaissance aircraft has provided a
few center fixes this afternoon, and found that Delta's passage
over land has resulted in weakening, and the initial wind speed is
set at 75 kt, which is based on a peak flight-level wind of 81 kt.
The aircraft also reported a minimum pressure of 977 mb on its
final center penetration, and data from the plane indicate that
there has been some increase in the radius of maximum winds.

Re-strengthening is anticipated over the next 24-36 hours while
Delta moves within a favorable upper-level environment and over the
relatively deep warm waters of the southern and central Gulf of
Mexico. Most of the intensity guidance brings Delta back up to
major hurricane status, and so does the official forecast. The
global models also significantly deepen Delta during the next 36
hours, lending confidence to re-intensification. After 36 hours,
increasing shear and cooler waters over the northern Gulf of Mexico
are likely to cause some decrease in intensity before Delta makes
landfall, however the hurricane's wind field is forecast to expand,
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.

Delta has been moving on a consistent northwestward heading of
305 degrees at about 15 kt. Delta should continue on this general
heading with some reduction in forward speed tonight and early
Thursday as it approaches the western extent of the subtropical
ridge. A mid- to upper-level trough over Texas is forecast to
slide eastward over the next couple of days, which is expected to
cause Delta to turn north-northwestward on Thursday, and northward
toward the northern Gulf coast by Friday. A faster northward to
north-northeastward motion in 48-60 hours will bring the center
onshore along the northern Gulf coast late Friday. The cross track
spread in the dynamical models has decreased this cycle, with the
model predictions converging on the previous NHC track forecast.
Therefore, little change has been made to the previous official
forecast, and it lies near the center of the now tightly clustered
guidance envelope.

Key Messages:

1. Winds and water levels along the northern coast of the Yucatan
Peninsula will gradually subside this evening. 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 life-threatening storm surge and dangerous
hurricane-force winds are likely 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 to isolated moderate river
flooding is likely Friday and Saturday from portions of the central
Gulf Coast 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 07/2100Z 22.1N 89.5W 75 KT 85 MPH
12H 08/0600Z 23.2N 91.2W 85 KT 100 MPH
24H 08/1800Z 24.8N 92.9W 95 KT 110 MPH
36H 09/0600Z 26.7N 93.4W 100 KT 115 MPH
48H 09/1800Z 29.1N 92.9W 90 KT 105 MPH
60H 10/0600Z 31.6N 91.9W 45 KT 50 MPH...INLAND
72H 10/1800Z 33.7N 90.5W 30 KT 35 MPH...INLAND
96H 11/1800Z 37.0N 85.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 12/1800Z...DISSIPATED

$$
Forecaster Brown

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Looks like a pretty good downgrade in intensity.

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however the hurricane's wind field is forecast to expand,
which will increase the storm surge and wind threats.

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Mike Seidel from The Weather Channel is in Morgan City.

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