278
WTNT44 KNHC 141631
TCDAT4

Hurricane Sally Special Discussion Number 13
NWS National Hurricane Center Miami FL AL192020
1130 AM CDT Mon Sep 14 2020

A NOAA Hurricane Hunter aircraft investigating Sally recently
measured peak flight-level winds of 88 kt at 700 mb and SFMR winds
of 78 kt north of the center, and an Air Force reconnaissance
aircraft just measured 79 kt flight-level winds at 700 mb. These
data indicate that Sally has rapidly strengthened into a hurricane
with an intensity of around 80 kt. In addition, data from the KEVX
WSR-88D show an eye forming at around 16,000 ft altitude. This
special advisory has been issued to increase the initial and
forecast intensity. Additional adjustments to the intensity forecast
could be required this afternoon. Only a slight adjustment was made
to the 12-h track forecast position based on the more northward and
eastward initial position.

KEY MESSAGES:

1. It is too early to determine where Sally's center will move
onshore given the uncertainty in the timing and location of Sally's
northward turn near the central Gulf Coast. Users should not focus
on the details of the official forecast track, since NHC's average
forecast error at 48 hours is around 80 miles, and dangerous storm
surge, rainfall, and wind hazards will extend well away from the
center.

2. An extremely dangerous and life-threatening storm surge is
expected for areas outside the southeastern Louisiana Hurricane and
Storm Damage Risk Reduction System from Port Fourchon, Louisiana, to
the Alabama/Florida border, where a Storm Surge Warning is in
effect. Residents in these areas should follow any advice given by
local officials.

3. Hurricane conditions are expected tonight within the Hurricane
Warning area in southeastern Louisiana and are expected by late
Tuesday within the Hurricane Warning area along the Mississippi and
Alabama coastline. Tropical storm conditions are likely to begin
later today and this evening in these areas and preparations
should be rushed to completion.

4. Life-threatening flash flooding is likely, as well as widespread
minor to isolated major flooding, on area rivers along and just
inland of the Central Gulf Coast. Significant flash and urban
flooding, as well as widespread minor to moderate river flooding is
likely across Mississippi and Alabama through the middle of the
week. Flooding impacts are expected to spread farther across the
Southeast through the week. Sally could continue to produce flash
flooding across the Florida peninsula and prolong existing minor
river flooding across west-central Florida through today.


FORECAST POSITIONS AND MAX WINDS

INIT 14/1630Z 28.7N 87.0W 80 KT 90 MPH
12H 15/0000Z 28.8N 87.8W 85 KT 100 MPH
24H 15/1200Z 29.2N 88.8W 90 KT 105 MPH
36H 16/0000Z 29.8N 89.1W 90 KT 105 MPH
48H 16/1200Z 30.8N 88.7W 65 KT 75 MPH...INLAND
60H 17/0000Z 31.8N 87.7W 30 KT 35 MPH...INLAND
72H 17/1200Z 32.6N 86.5W 25 KT 30 MPH...INLAND
96H 18/1200Z 33.1N 84.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 19/1200Z...DISSIPATED

$$
Forecaster Brown
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