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Tropical Storm Gordon Discussion Number  10
NWS National Hurricane Center Miami FL       AL072018
400 PM CDT Tue Sep 04 2018

Gordon has been undergoing another convective bursting phase during
the past few hours, with a sharp increase in Doppler velocity
values noted between 9,000-12,000 ft. Some peak velocity values
have been in excess of 80 kt, but average values have been around
65-67 kt, which supports an advisory intensity of 60 kt. Another
reconnaissance mission will be conducted in Gordon in a few hours,
which provide additional intensity and pressure data.

The initial motion estimate is 310/13 kt. There remains no
significant change to the previous NHC forecast track or reasoning.
The new model guidance has shifted slightly to the east, but not
enough to make any appreciable changes to the previous forecast
track. As a result, Gordon is expected to move northwestward toward
the Mississippi coastline, and the cyclone will make landfall in
that area around 0300 UTC. After landfall, steering currents are
still expected to weaken, causing Gordon to slow down considerably.
The slower forward speed, which will be near 5 kt at times, will act
to enhance the heavy rainfall potential. By Friday, a mid- to
upper-level trough and a cold front are forecast to cause a break
int the subtropical ridge, allowing Gordon to turn northward on
Friday, and move northeastward on Saturday. Gordon's remnant
circulation is expected to merge with a cold front by Sunday. The
new official track forecast is close to a blend of the consensus
models HCCA, FSSE, and TVCA,

Gordon still has another 6 hours or so over warm waters near 30C,
which in combination with an upper-level environment of diffluent
southeasterly upper-level flow and increased surface convergence due
to land interaction will provide a brief window of opportunity for
Gordon to reach hurricane strength before landfall. Once Gordon
moves inland, the small circulation is expected to spin down
quickly, with Gordon becoming a remnant low by 48 hours.

Key Messages:

1. Gordon is expected to bring life-threatening storm surge and
hurricane conditions to portions of the central Gulf Coast, where a
Storm Surge Warning and Hurricane Warning are in effect. The highest
storm surge is expected along the coasts of Mississippi and Alabama
from the Mouth of the Pearl River to Dauphin Island tonight and
early Wednesday. Tropical storm conditions and storm surge will also
affect portions of the western Florida Panhandle.

2. Heavy rainfall from Gordon will affect the western Florida
Panhandle, southwest Alabama, southern and central Mississippi,
northeastern Louisiana, and southern Arkansas, where totals could
reach as high as 12 inches. This rainfall will cause flash flooding
in portions of these areas.

FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 29.4N  87.8W   60 KT  70 MPH
 12H  05/0600Z 30.7N  89.3W   55 KT  65 MPH...INLAND
 24H  05/1800Z 32.2N  90.7W   30 KT  35 MPH...INLAND
 36H  06/0600Z 33.2N  91.9W   25 KT  30 MPH...INLAND
 48H  06/1800Z 34.0N  93.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  07/1800Z 35.7N  94.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  08/1800Z 38.1N  93.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  09/1800Z 41.0N  89.5W   20 KT  25 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

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