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Tropical Storm Gordon Discussion Number   7
NWS National Hurricane Center Miami FL       AL072018
1100 PM EDT Mon Sep 03 2018

WSR-88D radar data from Tampa shows that the small inner core of
Gordon has lost some organization during the past few hours, and
GOES-16 satellite imagery and recent aircraft fixes indicate that
the low-level center is located near the southwestern edge of the
main convective mass.  This suggests that there may be some light to
moderate westerly shear affecting the cyclone.  The Air Force
Reserve reconnaissance aircraft recently measured peak 850-mb
flight-level winds of 57 kt, and SFMR winds of 50-55 kt.  A blend
of these data yields an initial wind speed estimate of 50 kt.

A UW/CIMSS shear analysis and the SHIPS model indicates that there
is about 10-15 kt of westerly shear over the system.  The SHIPS
guidance shows a slight relaxation of the shear during the next
12-18 hours while the system moves over the warm waters of the Gulf
of Mexico, which should allow for some strengthening.  However,
Gordon is a small tropical cyclone and subtle changes in shear
(both up and down) can result in fairly quick intensity changes for
systems like this.  The NHC intensity forecast assumes that shear
will not be prohibitive and that Gordon will become a hurricane
before reaching the northern Gulf coast.  The NHC intensity
forecast is close to the SHIPS guidance through 24 hours, then
follows the HFIP corrected consensus after landfall which shows
Gordon weakening rapidly over land.

Gordon is moving west-northwestward at about 15 kt.  The tropical
storm is expected to maintain a west-northwestward to northwestward
heading during the next few days while it moves around the
southwestern portion of a large deep-layer ridge centered over the
Mid-Atlantic states.  After that time, the cyclone should decelerate
as it moves around the western periphery of the ridge.  The track
guidance continues to be tightly clustered through 72 h, and no
significant changes were required to the previous NHC track
forecast.

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. Residents
in these areas should listen to advice from their local officials.
All preparations to protect life and property should be rushed to
completion, as tropical storm conditions are expected to arrive in
the warning areas Tuesday afternoon.

2. Heavy rainfall from Gordon will affect southern Alabama, southern
Mississippi and Louisiana, where totals could reach as high as 8
inches. This rainfall could cause flash flooding.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 26.9N  84.3W   50 KT  60 MPH
 12H  04/1200Z 28.3N  86.3W   55 KT  65 MPH
 24H  05/0000Z 30.0N  88.6W   65 KT  75 MPH
 36H  05/1200Z 31.6N  90.3W   40 KT  45 MPH...INLAND
 48H  06/0000Z 32.9N  91.6W   25 KT  30 MPH...INLAND
 72H  07/0000Z 34.6N  93.9W   20 KT  25 MPH...INLAND
 96H  08/0000Z 36.5N  94.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  09/0000Z 39.5N  93.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

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