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Tropical Storm GORDON


Tropical Storm Gordon Discussion Number   5
NWS National Hurricane Center Miami FL       AL072018
1100 AM EDT Mon Sep 03 2018

Surface observations from the Florida Keys and southeast Florida,
along with Doppler velocity data from the Miami radar, indicate that
Gordon has continued to become organized this morning. The center
of the cyclone passed over Key Largo between 1100-1200 UTC,
producing a west wind in Islamorada and also at an observing site
in Florida Bay. Doppler velocity data and surface observations
support an intensity of 40 kt for this advisory. An Air Force
Reserve Unit reconnaissance aircraft is currently investigating

The initial motion estimate is 300/14 kt. The latest model
guidance has shifted slightly to the right, but this is likely due
to the more northerly initial position. Other than that, the models
remain tightly packed and agree on a general west-northwestward to
northwestward motion for the next 48 hours right up until landfall
as the strong ridge to the north of Gordon moves little. The new NHC
forecast track was adjusted a little to the right of the previous
advisory track, but not as far to the east as some of the model
guidance out of respect for the reliable ECMWF deterministic run,
which is located on the southern edge of the guidance and shows
landfall near the mouth of the Mississippi River, a solution that is
also supported by the new 0600Z short-range UKMET model run.

Gordon's appearance in both radar and satellite imagery has
continued to improve over the past several hours. The GFS- and
ECMWF-based SHIPS models indicate that westerly to northwesterly
vertical wind shear of about 10 kt is allegedly affecting Gordon,
but there are no indications of that in satellite imagery that I
can see. The cirrus outflow has continued to expand in all
quadrants, so the analyzed westerly shear is likely an artifact of
the small circulation being positioned so close to the strong trough
located its west. Since Gordon will be moving over sea-surface
temperatures near 30 deg C during the next 36-48 hours, and be near
or underneath an upper-level anticyclone, steady strengthening seems
likely. It is possible that Gordon could peak as a Category 1
hurricane after 36 hours, just before landfall occurs. For that
reason, a Hurricane Watch has been issued for portions of the
central Gulf Coast. The new intensity forecast is above the previous
advisory, and is close to a blend of the consensus models

Key Messages:

1. Gordon will bring heavy rainfall and tropical storm conditions
to portions of South Florida and the Florida Keys today and a
Tropical Storm Warning remains in effect for these areas.

2. Gordon is expected to bring life-threatening storm surge to
portions of the central Gulf Coast and a Storm Surge Warning has
been issued from the Mouth of the Pearl River to the Mississippi-
Alabama border. Residents in these areas should listen to advice
from their local officials and all preparations to protect life
and property should be rushed to completion.

3. A Tropical Storm Warning and Hurricane Watch are in effect for
portions of the central Gulf Coast. Tropical storm conditions are
expected to reach those areas late Tuesday, with hurricane
conditions possible in the watch area.

4. 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.


INIT  03/1500Z 25.3N  81.3W   40 KT  45 MPH
 12H  04/0000Z 26.5N  83.4W   45 KT  50 MPH
 24H  04/1200Z 28.1N  86.0W   50 KT  60 MPH
 36H  05/0000Z 29.9N  88.4W   60 KT  70 MPH
 48H  05/1200Z 31.3N  90.3W   40 KT  45 MPH...INLAND
 72H  06/1200Z 33.9N  93.2W   25 KT  30 MPH...INLAND
 96H  07/1200Z 34.8N  94.9W   20 KT  25 MPH...INLAND
120H  08/1200Z 37.6N  95.1W   20 KT  25 MPH...POST-TROP/REMNT LOW

Forecaster Stewart