ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
 
Tropical Depression Eleven Discussion Number   1
NWS National Hurricane Center Miami FL       AL112021
1100 PM AST Sat Aug 28 2021
 
Before sunset this evening, visible satellite images showed that a 
well-defined low level circulation was developing in association 
with the disturbance over the subtropical central Atlantic. 
However, up until a couple of hours ago, the system lacked 
sufficient organized deep convection to be considered a tropical 
cyclone by definition. Since that time, a deep convective burst has 
increased in size near, and to the east of the estimated 
center. In addition, a curved band has begun to develop over the 
southeastern portion of the circulation. Based on this increase in 
convective organization, advisories are being initiated on Tropical 
Depression Eleven. There was no ASCAT data this evening over the 
cyclone, so the initial intensity of 30 kt is based on the latest 
Dvorak CI number from TAFB. 

The initial motion of the depression is 050/10 kt. The cyclone is 
embedded in southwesterly flow to the southeast of a mid- to 
upper-level trough and an associated cold front. This flow is 
forecast to increase as the cold front approaches the cyclone, 
resulting in the system accelerating northeastward over the next day 
or so. Once the cyclone interacts with this frontal boundary in a 
couple of days, a turn to the north is expected. The model guidance 
is in very good agreement on this scenario, and the NHC track 
forecast lies in the middle of the consensus tracks. 

Baroclinic forcing and upper-level diffluence should aid in 
intensifying the depression over the next 24 h, despite increasing 
shear. By 36 h, the combination of interaction with the cold front 
and passage over much cooler waters should result in extratropical 
transition. The system is then forecast to become absorbed by a 
larger low pressure system by midweek. The NHC intensity forecast 
is near the various multi-model consensus solutions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0300Z 33.0N  49.7W   30 KT  35 MPH
 12H  29/1200Z 34.6N  47.1W   35 KT  40 MPH
 24H  30/0000Z 36.8N  43.4W   45 KT  50 MPH
 36H  30/1200Z 39.5N  39.2W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  31/0000Z 43.4N  36.4W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  31/1200Z 47.9N  36.3W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  01/0000Z...DISSIPATED
 
$$
Forecaster Latto
 
NNNN