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Tropical Depression NINETEEN

Tropical Depression Nineteen Discussion Number   1
NWS National Hurricane Center Miami FL       AL192020
500 PM EDT Fri Sep 11 2020
GOES-16 1-minute satellite data show that the system near the 
Bahamas that we have been monitoring for the past couple of days 
has quickly organized into a tropical depression.  Very deep 
convection has formed near the center, and the 1-min data now shows 
enough north and northwest flow to indicate that a well-defined 
center is present.  The initial wind speed is 30 kt in agreement 
with recent ship data.  

It is uncertain whether the large burst of convection over the 
center will continue and cause the depression to become a tropical 
storm before reaching Florida.  However, since it is only a 5 kt 
increase from the current intensity, it is possible that tropical 
storm conditions could still occur along the southeast Florida coast 
late tonight, and a tropical storm watch has been issued.  
Otherwise, after the system reaches the eastern Gulf of Mexico, 
steady intensification is expected through the weekend due to 
expected light wind shear and very warm water. Some increase in 
shear could occur over the northern Gulf of Mexico but that is 
uncertain at this time.  The first forecast will stay conservative 
and only show a peak intensity of 60 kt in 3 to 4 days, but do not 
be surprised if that is revised upward on later forecasts once 
other models better initialize the depression.

An uncertain estimate of the initial motion is 285/7. Strong 
ridging over the southeastern United States is expected to steer the 
cyclone to the west-northwest then northwest as a mid-latitude 
trough erodes the western side of the ridge over the weekend.  The 
forecast gets tricky after that because the bulk of the guidance 
suggests the trough isn't deep enough to recurve the system, and 
instead it gets left behind, moving slowly westward early next week 
due to weak ridging over the southern Plains.  The NHC forecast is 
near the corrected-consensus guidance.  The uncertainty in the 
track forecast is much larger than normal after 48 hours, as small 
changes in the forecast steering flow could result in this system 
moving over the northern Gulf Coast faster and to the northeast of 
what is shown here. As a result, the risk of seeing direct impacts 
from this system extends well outside the cone of uncertainty, even 
more so than usual in this case. 


1. Heavy rainfall is expected to produce isolated flash flooding 
over portions of central and southern Florida and prolong existing 
minor river flooding in the Tampa Bay area. 

2. Tropical storm conditions are possible tonight along the 
southeast Florida coast where a Tropical Storm Watch is in effect.  

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 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 tonight and Saturday.
INIT  11/2100Z 25.4N  79.0W   30 KT  35 MPH
 12H  12/0600Z 25.7N  80.1W   30 KT  35 MPH
 24H  12/1800Z 26.2N  81.9W   30 KT  35 MPH
 36H  13/0600Z 27.3N  83.8W   35 KT  40 MPH
 48H  13/1800Z 28.4N  85.2W   45 KT  50 MPH
 60H  14/0600Z 29.1N  86.3W   55 KT  65 MPH
 72H  14/1800Z 29.5N  87.4W   60 KT  70 MPH
 96H  15/1800Z 30.0N  89.0W   60 KT  70 MPH
120H  16/1800Z 31.0N  91.0W   25 KT  30 MPH...INLAND
Forecaster Blake