3 Sep Mon 2018

Tropical Storm Florence Discussion Number 16
NWS National Hurricane Center Miami FL AL062018
500 AM AST Mon Sep 03 2018

The structure of Florence has recovered overnight. Several recent
microwave images indicate that the tropical storm’s center is still
dislocated to the south of most of the associated convection, but
convective banding has increased. There is also evidence that
Florence has developed better defined low-level inner-core.
Satellite intensity estimates have increased and now range from 45
to 60 kt. As a compromise of the various estimates, the initial
intensity has been raised slightly to 50 kt, but its worth noting
that this increase is within the noise level of our ability to
observe the intensity of tropical storms over the open ocean.

Based on SHIPS diagnostics, the southwesterly shear affecting
Florence could remain moderate for the next 12 h, and some slight
intensification is possible. However, by 24 h, an increase in the
shear should kick off a gradual weakening trend. By the end of the
forecast period, the tropical storm is forecast to re-intensify
while it moves over warmer SSTs and the environmental shear
decreases. Given the improved current structure of Florence, the new
official intensity forecast shows slight intensification for the
first 12 h. Beyond that time, the models are in good agreement and
the NHC forecast is near the middle of the relatively tight
intensity guidance envelope.

The tropical storm is still moving west-northwestward, at an
estimated 14 kt. A continued west to west-northwest motion is
forecast by all the global models for the next couple of days. By
the end of the forecast period, nearly all of the guidance shows a
turn toward the northwest, and the main source of uncertainty in
the track forecast continues to be exactly when and to what extent
Florence will make this turn. At this point I have no reason to
depart from the various consensus models, and the track forecast is
very close to the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 18.0N 37.5W 50 KT 60 MPH
12H 03/1800Z 18.3N 39.6W 55 KT 65 MPH
24H 04/0600Z 18.7N 42.0W 50 KT 60 MPH
36H 04/1800Z 19.3N 44.2W 45 KT 50 MPH
48H 05/0600Z 20.0N 46.5W 45 KT 50 MPH
72H 06/0600Z 22.2N 51.1W 40 KT 45 MPH
96H 07/0600Z 24.5N 54.5W 45 KT 50 MPH
120H 08/0600Z 26.0N 57.0W 55 KT 65 MPH

$$
Forecaster Zelinsky

Tropical Storm Gordon Special Discussion Number 4
NWS National Hurricane Center Miami FL AL072018
830 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 the disturbance has developed a closed surface circulation and
a well-defined center. Recent observations from a Weatherflow site
at Carys Fort Reef and radar data support increasing the maximum
winds to at least 40 kt. As a result of these data, the system has
been upgraded to Tropical Storm Gordon, the seventh named system of
the 2018 Atlantic hurricane season. An Air Force Reserve Unit
reconnaissance aircraft is enroute to investigate Gordon.

The initial motion estimate is 300/15 kt and the previous forecast
track remains unchanged. The intensity forecast was adjusted upward
in the first 24 to 36 hours to account for the initial increase in
intensity. Some additional adjustments may be required after the
reconnaissance aircraft completes its mission and provides more
detailed information on the stricture and intensity of Gordon.

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 is in effect for these areas.

2. A Tropical Storm Warning is in effect for portions of the
central Gulf Coast, and tropical storm conditions are expected in
those areas beginning late Tuesday. Heavy rainfall from Gordon will
affect portions of the central Gulf Coast over the next few days,
including areas that have already received heavy rainfall from a
different weather system. Interests in these areas should monitor
products from their local National Weather Service office.

FORECAST POSITIONS AND MAX WINDS

INIT 03/1230Z 25.1N 80.7W 40 KT 45 MPH
12H 03/1800Z 25.7N 82.1W 45 KT 50 MPH
24H 04/0600Z 27.2N 84.8W 50 KT 60 MPH
36H 04/1800Z 28.8N 87.4W 50 KT 60 MPH
48H 05/0600Z 30.4N 89.7W 50 KT 60 MPH
72H 06/0600Z 33.0N 92.7W 30 KT 35 MPH…INLAND
96H 07/0600Z 34.0N 95.0W 25 KT 30 MPH…INLAND
120H 08/0600Z 35.5N 96.0W 20 KT 25 MPH…POST-TROP/REMNT LOW

$$
Forecaster Stewart