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Hurricane SALLY

Hurricane Sally Discussion Number  14
NWS National Hurricane Center Miami FL       AL192020
400 PM CDT Mon Sep 14 2020
After the rapid spin up of the inner core late this morning, the 
most recent aircraft passes through the center have not found any 
higher flight-level winds, however there have been a few SFMR winds 
of 85-90 kt reported.  Using a blend of the flight-level and SFMR 
winds the initial intensity has been increased to 85 kt for this 
advisory.  The next Air Force and NOAA aircraft have begun to sample 
the storm.  Now that Sally has developed an inner core, the 
favorable atmospheric and ocean conditions of low vertical wind 
shear and warm water should allow for additional strengthening 
tonight while the system moves over the north-central Gulf of 
Mexico, and Sally could approach major hurricane strength.  On 
Tuesday, the global models are predicting an increasing in 
southwesterly flow aloft, and this increase in shear, the potential 
for land interaction, and some upwelling over the shallower shelf 
waters over the northern Gulf should slow the intensification 
process.  The NHC intensity forecast is again near the upper-end of 
the guidance envelope in best agreement with the HWRF and HFIP 
corrected consensus models.
Sally did not move much earlier today as the center re-formation
took place, but it appears that a slow west-northwestward to
northwestward motion has resumed.  Weak ridging over the
southeastern United States is expected to steer Sally generally
west-northwestward through early Tuesday.  After that time, steering
currents weaken and a slow northward motion is forecast as a weak
mid-level trough develops over the the central United States.  This
trough is forecast to slide eastward, allowing Sally to begin a
slow north-northeastward or northeastward motion. The specific
timing and location of the turn will be critical as to the eventual
location and timing of landfall along the north-central Gulf Coast.
The UKMET and ECMWF models show a more northeastward motion after
the turn and have trended eastward, with the ECMWF much slower than
the remainder of the guidance.  The NHC track has been adjusted
eastward, and this requires and eastward extension of the hurricane
warning.  The new track most closely follows the GFS and it ensemble
mean, but lies to the west of the various consensus aids, so some
additional eastward adjustments could be needed in subsequent
Given the uncertainty in the timing and location of the northward
turn and the lack of well-defined steering currents, users are
reminded to not focus on the exact forecast track or the specific
timing and location of landfall.  Hurricane-force winds, dangerous
storm surge, and flooding rainfall will affect a large portion of
the north-central Gulf Coast during the next few days.
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 36 to 48 hours is around 60 to 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 Okaloosa/Walton County Line in the Florida Panhandle, 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 late tonight or early Tuesday
within the Hurricane Warning area in southeastern Louisiana and are
expected by late Tuesday and Tuesday night within the Hurricane
Warning area along the Mississippi and Alabama coastlines and the
western Florida Panhandle. Tropical storm conditions are likely to
begin 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.
INIT  14/2100Z 28.8N  87.4W   85 KT 100 MPH
 12H  15/0600Z 29.2N  88.2W   95 KT 110 MPH
 24H  15/1800Z 29.7N  88.7W   95 KT 110 MPH
 36H  16/0600Z 30.4N  88.6W   90 KT 105 MPH...INLAND
 48H  16/1800Z 31.3N  88.0W   55 KT  65 MPH...INLAND
 60H  17/0600Z 32.2N  86.8W   30 KT  35 MPH...INLAND
 72H  17/1800Z 32.9N  85.5W   25 KT  30 MPH...INLAND
 96H  18/1800Z 33.5N  83.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  19/1800Z...DISSIPATED
Forecaster Brown