Potential Tropical Cyclone Sixteen Forecast Discussion Number 4


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Issued at 400 AM CDT Fri Oct 18 2019

WTNT41 KNHC 180833

Potential Tropical Cyclone Sixteen Discussion Number 4
NWS National Hurricane Center Miami FL AL162019
400 AM CDT Fri Oct 18 2019

Although the convection associated with the disturbance has
increased during the past few hours, there is no evidence that a
well-defined center has formed yet. One can observe several swirls
of low clouds rotating within a larger gyre. Most of the global
models forecast that the system will become better organized
later today, and given the current trend, NHC forecasts that a
tropical or most likely a subtropical cyclone will form later this
morning. A reconnaissance plane will investigate the disturbance in
a few hours.

The disturbance is located to the east of an upper trough which
is digging along the western Gulf of Mexico, and the upper-level
diffluence caused by the trough should induce some strengthening
during the next 24 hours or so before the system moves inland.
However, the simulated convection by the GFS and the ECMWF models
resembles a comma-shape pattern which is characteristic of a
subtropical cyclone. After landfall, the cyclone is expected to
become extratropical and gradually weaken while it moves
northeastward near the southeast U.S. coast. By day 5, the low is
forecast to be absorbed by a front over the western Atlantic.

Since the center is not well defined, the initial motion is highly
uncertain. The best estimate is toward the northeast or 045 degrees
at 12 kt. The system should accelerate later today and continue
toward the northeast embedded within the flow ahead of the trough.
Track models are in remarkably good agreement, and the NHC
forecast is in the middle of the tight guidance envelope.

Regardless of the exact evolution of the system, portions of the
northern coast of the Gulf of Mexico will experience strong winds,
locally heavy rains, and storm surge Friday and Saturday. Similar
impacts are expected across portions of the Atlantic coast of the
southeastern United States Saturday and Sunday.

Key Messages:

1. There is a danger of life-threatening storm surge inundation of
up to 5 feet above ground level beginning today along the Florida
Gulf Coast from Indian Pass to Clearwater, where a Storm Surge
Warning is in effect. Residents in these areas should follow advice
given by local officials.

2. Tropical storm force winds are likely by later today along
portions of the central and eastern Gulf Coast, where tropical storm
warnings are in effect. Regardless of the exact track and intensity
of the system, these winds will cover a large area, especially east
of the center.

3. Isolated flash flooding is possible along the central and eastern
Gulf Coast and southeastern United States coast from today through
Saturday night. Since soils across the southeast are dry, the
risk of flash flooding will be confined to the immediate coast where
heavier rainfall is possible.

4. Wind and coastal flooding hazards along the U.S. East Coast will
be covered by non-tropical watches and warnings issued by local NWS
offices, since the system is expected to lose any tropical
characteristics after it moves inland along the Gulf Coast.


12H 18/1800Z 26.8N 89.8W 40 KT 45 MPH...TROPICAL STORM
24H 19/0600Z 29.0N 87.0W 45 KT 50 MPH
36H 19/1800Z 31.5N 84.5W 35 KT 40 MPH...INLAND
48H 20/0600Z 33.5N 80.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
72H 21/0600Z 37.0N 72.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 22/0600Z 37.5N 69.5W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 23/0600Z...DISSIPATED

Forecaster Avila

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