[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 082041
TCDAT4

Hurricane Michael Discussion Number   9
NWS National Hurricane Center Miami FL       AL142018
400 PM CDT Mon Oct 08 2018

Data from an Air Force Reserve hurricane hunter aircraft that was
in the storm until about 1700 UTC continued to indicate that the
hurricane was deepening.  The pressure had fallen to 978 mb on
the final fix, but the aircraft was still not able to sample the
northeastern portion of the storm due to the close proximity of
land.  The initial intensity has been increased to 70 kt based on a
blend of Dvorak satellite classifications and the continued
deepening that was observed.

The upper-level outflow has gradually improved over Michael but it
is still somewhat restricted over the western portion of the storm.
There has been no significant change to the intensity forecast
thinking.  The moderate shear that has been affecting the cyclone is
not expected to prevent strengthening while Michael moves over the
warm waters of the eastern Gulf of Mexico.  Although the statistical
guidance is somewhat lower this cycle, the regional hurricane and
global models still favor steady to rapid strengthening, and the NHC
forecast is closest to the Florida State Superensemble and the HFIP
corrected consensus model.

Aircraft and satellite fixes show that Michael has been wobbling as
it moves generally northward. Smoothing through the wobbles gives a
long-term initial motion estimate of 355/8 kt. Michael is forecast
to move north-northwestward to northward between a deep-layer ridge
over the western Atlantic and a trough over the west-central United
States. The trough is forecast move eastward, causing Michael to
turn northeastward in 36 to 48 hours, and the cyclone should then
accelerate northeastward as it enters the mid-latitude westerly
flow. The 1200 UTC dynamical models have converged on both the
track and forward speed through the first 48 to 72 hours. The
updated NHC track has been nudged slightly westward through 48 hours
to be closer to the latest consensus aids.

It should be noted that the location and magnitude of peak storm
surge flooding is very sensitive to small changes in the track,
intensity, and structure of the hurricane. Since there is still
uncertainty in all of these parameters, the official NHC storm surge
forecast and watch/warning areas includes various plausible
scenarios. Regardless of the eventual track and intensity of
Michael, life-threatening storm surge inundation is expected along
portions of the Florida Panhandle and Big Bend/Nature Coast, and the
storm surge watch has been upgraded to a storm surge warning for
parts of this area.

The NOAA G-IV aircraft is conducting a synoptic surveillance mission
over the Gulf of Mexico and dropsondes from that mission will be
assimilated into the 0000 UTC numerical models runs.

Key Messages:

1. Life-threatening storm surge is likely along portions of the
coasts of the Florida Panhandle, Big Bend, and Nature Coast, and a
storm surge warning is in effect for these areas. Residents in these
areas should follow all advice given by their local officials.

2. A hurricane warning has been issued for portions of the Florida
Gulf Coast, and everyone in these areas should prepare for
life-threatening winds associated with the core of Michael.
Damaging winds will also extend inland across portions of the
Florida Panhandle, southern Georgia, and southeast Alabama as
Michael moves inland.

3. Heavy rainfall from Michael could produce life-threatening flash
flooding from the Florida Panhandle and Big Bend region into
portions of Georgia and South Carolina.

4. Hurricane conditions will continue in portions of western Cuba
through this evening, where a hurricane warning is in effect.

5. Michael is expected to produce heavy rainfall and flash flooding
over portions of western Cuba and the northeastern Yucatan Peninsula
of Mexico during the next couple of days.

FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 22.2N  85.2W   70 KT  80 MPH
 12H  09/0600Z 23.7N  85.7W   85 KT 100 MPH
 24H  09/1800Z 25.7N  86.4W   95 KT 110 MPH
 36H  10/0600Z 27.9N  86.6W  105 KT 120 MPH
 48H  10/1800Z 30.2N  85.8W  100 KT 115 MPH...NEAR THE COAST
 72H  11/1800Z 34.5N  80.5W   45 KT  50 MPH...INLAND
 96H  12/1800Z 39.8N  68.8W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  13/1800Z 46.2N  50.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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