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Tropical Depression Nineteen Discussion Number   3
NWS National Hurricane Center Miami FL       AL192020
500 AM EDT Sat Sep 12 2020

Surface observations and Doppler radar data indicate that Tropical 
Depression Nineteen was close to tropical storm strength when it 
moved ashore in Miami-Dade county just after 06Z.  The central 
pressure had dropped to near 1004 mb, and the radar showed winds of 
45-50 kt above the surface just to the northeast of the center, 
associated with a strong convective burst.  However, there were no 
surface observations of 35-kt sustained winds, and the highest 
reported gusts were in the 35-40 kt range. Based on the available 
data, the initial intensity remains 30 kt. It should be noted 
that since landfall, the strong convective burst near the 
low-level center has weakened considerably.

The cyclone has turned left during the past several hours, and the 
initial motion is a somewhat uncertain 270/8 kt.  The subtropical 
ridge extending from the southeastern United States eastward over 
the Atlantic should steer the cyclone generally west-northwestward 
through Sunday.  After that time, the ridge is forecast to weaken 
due to an approaching mid-latitude trough.  This should result in a 
northwestward motion through from Sunday night into the middle 
portion of next week, with the cyclone expected to reach the 
northern Gulf coast around the 96 h point.  The latest track 
guidance now has the cyclone responding more strongly to the trough 
and turning northward by 120 h.  The new forecast track is shifted 
a little south of the previous track through 72 h based on the 
initial position and motion.  At 120 h, the new track is nudged to 
the east of the old track, but it still lies to the west of the 
consensus models. 

The depression is currently experiencing some northerly vertical 
wind shear, and the latest global model runs are showing more shear 
affecting the system as it crosses the Gulf of Mexico than earlier. 
However, since the cyclone is going to be over very warm sea 
surface temperatures and in a moist environment, the intensity 
guidance still shows it strengthening to near hurricane strength, 
or stronger, before it reaches the northern Gulf coast.  Due to the 
uncertainty about the amount of shear, the new intensity forecast 
has only minor adjustments from the previous forecast.  However, 
it lies below the various intensity consensus models.
 
Users are reminded to not to focus on the exact details of the 
track or intensity forecast as the average NHC track error at 96 h 
is around 150 miles and the average intensity error is around
15 mph.  In addition, winds, storm surge, and rainfall hazards will
extend far from the center.
 
KEY MESSAGES:
 
1. Tropical Depression Nineteen is expected to produce isolated to 
scattered flash flooding across portions of west-central and 
southern Florida and prolong existing minor river flooding across 
Central Florida through Sunday. Scattered flash flooding is also 
possible across portions of the central Gulf Coast Sunday through 
Tuesday morning. 

2. Tropical storm conditions are possible by Sunday night in 
portions of the Florida Panhandle, where a Tropical Storm Watch has 
been issued.  Wind gusts to tropical-storm force could occur over 
portions of the southern Florida Peninsula today.
 
3. The system is forecast to strengthen to near hurricane intensity
by early next week as it moves across the northeastern Gulf of
Mexico. Dangerous impacts from storm surge, wind, and heavy rainfall
will be possible along the Gulf Coast from the Florida Panhandle to
southeastern Louisiana late this weekend and early next week.
Residents in these areas should monitor the progress of this system
and updates to the forecast, as Storm Surge, Tropical Storm or
Hurricane watches could be issued later today.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0900Z 25.6N  80.7W   30 KT  35 MPH...INLAND
 12H  12/1800Z 26.1N  82.0W   30 KT  35 MPH...OVER WATER
 24H  13/0600Z 26.9N  83.8W   35 KT  40 MPH
 36H  13/1800Z 27.9N  85.4W   40 KT  45 MPH
 48H  14/0600Z 28.7N  86.6W   50 KT  60 MPH
 60H  14/1800Z 29.3N  87.7W   60 KT  70 MPH
 72H  15/0600Z 29.6N  88.5W   60 KT  70 MPH
 96H  16/0600Z 30.5N  90.0W   55 KT  65 MPH...INLAND
120H  17/0600Z 31.5N  90.5W   25 KT  30 MPH...INLAND
 
$$
Forecaster Beven
 
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