[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 100252
TCDAT4

Hurricane Michael Discussion Number  14
NWS National Hurricane Center Miami FL       AL142018
1000 PM CDT Tue Oct 09 2018

Data from Air Force Reserve and NOAA Hurricane Hunter aircraft this
afternoon and evening indicate that Michael has been undergoing a
rapid deepening phase with the pressure having dropped to 947 mb, a
decrease of 20 mb between 1800Z and 0200Z with most of those
pressures falls occurring during the past few hours. Michael's eye
has become more distinct in GOES-16 high-resolution infrared
satellite imagery, with a solid ring of cloud top temperatures
colder than -75 deg C surrounding the warming eye. Some cloud tops
in the eyewall have been as cold as -88C, which is very impressive
for a Gulf system. The peak 8000-ft flight-level winds measured by
the NOAA aircraft thus far has been 130 kt and the strongest SFMR
surface wind speed observed has been 110 kt in the same location as
the peak flight-level winds. Based on these wind data, along with a
central pressure of 947 mb, Michael's intensity has been increased
to 110 kt. Satellite intensity estimates from TAFB and SAB, along
with objective estimates from UW-CIMSS ADT and NHC, support an
intensity of 115-127 kt. However, those also estimates also would
support a central pressure of about 935 mb, which the aircraft has
not measured thus far.

The initial motion estimate is due north, or 360/10 kt. Michael is
essentially on the previous advisory track, and there is no
significant change to the previous track forecast discussion. The
models have settled in a stable forecast pattern, which calls for
Michael to remain embedded within deep southerly flow for the next
24 hours between a  substantial ridge to the east and a highly
amplified mid-latitude trough moving eastward across the western and
central U.S. and northern Mexico. As a result, the dangerous
hurricane is expected to move northward to north-northeastward and
make landfall along the coast of the central panhandle of Florida by
late Wednesday afternoon. After landfall, increasing southwesterly
flow ahead of the approaching deep-layer trough is expected to
accelerate Michael toward the northeast through 48 h, with the
cyclone moving across the southeastern U.S. late Wednesday and
Thursday, and emerging over the western Atlantic by early Friday. A
continued northeastward motion at forward speeds of 30-40 kt is
forecast at 72-120 h when Michael is expected to be an extratropical
cyclone. The new NHC forecast track is essentially just an update of
the previous advisory track, and lies close to the tightly packed
consensus models TVCN, TVCX, TCON, and NOAA-HCCA.

Similar to the previous advisory, the environment ahead of Michael
is expected to remain conducive for additional strengthening until
landfall occurs due to SSTs of at least 85 deg F beneath the
hurricane, combined with decreasing vertical wind shear along with
the shear vector shifting from current west-northwesterly to a less
hostile southwesterly component, which will be more along Michael's
forecast track. As a result, Michael is now explicitly forecast to
become a category 4 hurricane before landfall occurs. After
landfall, significant weakening is expected while Michael moves over
the southeastern United States, but the cyclone is forecast to
re-strengthen over the western Atlantic due to baroclinic forcing
after it merges with a front and becomes extratropical on Friday.
The new intensity forecast closely follows a blend of the IVCN,
HCCA, and FSSE consensus models throughout the 120-h period.

Tropical storm conditions are expected to reach the hurricane
warning area by Wednesday morning, so all preparations should be
rushed to completion.

Key Messages:

1. Life-threatening storm surge is likely along portions of the
coasts of the Florida Panhandle, Big Bend, and Nature Coast, where
a storm surge warning is in effect. The worst storm surge is
expected between Mexico Beach and Keaton Beach, where 9 to 13 feet
of inundation is possible. Water levels will rise well in advance of
the center of Michael, and residents within the storm surge warning
area should finish preparations to protect life and property today.

2. Everyone in the hurricane warning area along the Florida Gulf
Coast should prepare for life-threatening major hurricane winds
associated with the core of Michael. Hurricane force winds will also
extend well 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, the Carolinas, and southeast Virginia.

4. Tropical storm conditions will likely affect portions of the
southeast U.S. coast from northeast Florida through North Carolina,
and tropical storm watches and warnings are in effect for these
areas.


FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 27.1N  86.5W  110 KT 125 MPH
 12H  10/1200Z 28.7N  86.2W  115 KT 130 MPH
 24H  11/0000Z 30.8N  84.9W   70 KT  80 MPH...INLAND
 36H  11/1200Z 33.0N  82.4W   40 KT  45 MPH...INLAND
 48H  12/0000Z 35.2N  78.6W   40 KT  45 MPH...INLAND
 72H  13/0000Z 40.8N  65.1W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  14/0000Z 47.2N  44.8W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  15/0000Z 51.2N  24.9W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart
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