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Tropical Depression Eleven Discussion Number   2
NWS National Hurricane Center Miami FL       AL112021
500 AM AST Sun Aug 29 2021

The depression continues to slowly organize this morning, with a 
distinct curved band stretching along the southeastern quadrant of 
the low-level circulation. However, the deep convection that was 
closer to the center earlier has recently been sheared off to the 
northeast due to increasing southwesterly vertical wind shear. The 
latest subjective Dvorak estimates from TAFB and SAB were T2.0/30 
kt and T1.5/25 kt respectively. The latest objective ADT guidance 
was a bit higher at T2.4/34 kt. Taking a blend of these estimates, 
the intensity was held at 30 kt for this advisory, though the 
depression appears close to becoming a tropical storm.

The depression is beginning to gradually accelerate, with the 
estimated motion now at 050/13 kt. A strong deep-layer trough will 
continue to steer the depression to the northeast in the short-term 
with increasing forward motion. After the system becomes a 
post-tropical cyclone, it is forecast to gradually pivot to the 
north and then northwest before dissipating in 72 hours. The latest 
NHC track forecast is a touch faster than the previous one, 
following the latest consensus track guidance. 

While vertical wind shear is expected to increase quite dramatically 
over the next 24-36 hours, strong baroclinic forcing should offset 
this negative factor and allow at least steady intensification in 
the short term especially as the cyclone accelerates. After 24 
hours, the system will be crossing into much cooler sea-surface 
temperatures, and extratropical transition will likely be ongoing as 
the system merges with an advancing frontal boundary. The latest NHC 
intensity forecast follows the HCCA consensus aid closely, and is 
just a bit stronger in the short-term helped by the fast forward 
motion, with a peak intensity of 50-kt just before extratropical 
transition occurs.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0900Z 34.0N  48.6W   30 KT  35 MPH
 12H  29/1800Z 35.8N  45.6W   40 KT  45 MPH
 24H  30/0600Z 38.5N  41.3W   50 KT  60 MPH
 36H  30/1800Z 41.8N  37.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  31/0600Z 45.9N  36.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  31/1800Z 50.0N  36.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  01/0600Z...DISSIPATED
 
$$
Forecaster Papin
 
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