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Tropical Depression Twelve Discussion Number   2
NWS National Hurricane Center Miami FL       AL122021
200 AM CVT Wed Sep 01 2021
 
Satellite images indicate that the depression is gradually becoming
better organized.  An area of deep convection has been persisting
near the center, and banding features are beginning to take shape.
The latest Dvorak estimates from TAFB and SAB have increased to
2.5/35 kt, which would support upgrading the system to a tropical
storm.  However, a recent ASCAT-B overpass around 2300 UTC showed
maximum winds in the 25-30 kt range in the northeastern quadrant,
and based on that data the initial intensity is held at 30 kt.
 
The tropical depression is moving fairly quickly to the
west-northwest at 17 kt.  The track forecast reasoning appears
fairly straightforward.  The cyclone is expected to move at a
relatively fast pace to the west or west-northwest during the next
couple of days as it remains on the south side of a strong mid-level
ridge.  After that time, a decrease in forward speed and a gradual
turn to the northwest are expected as the system nears the
southwestern side of the ridge.  Although most of the models agree
on the synoptic steering pattern, there is a fair amount of spread
from days 3 to 5 in how soon the northwestward turn will occur. The
NHC track forecast lies near the middle of the guidance envelope and
is a little to the north of the previous one based on the more
poleward initial position.
 
Since the system is expected to be over relatively warm water and in 
an air mass of low wind shear and abundant moisture, steady 
strengthening is expected during the next couple of days.  The 
depression is likely to become a tropical storm within the next 12 
hours and a hurricane in 36 to 48 hours.  Beyond a few days, an 
increase in shear and drier air should slow the rate of 
intensification.  The NHC intensity forecast follows the trend of 
the HCCA, IVCN, and IVDR models.  In addition, the global models all 
show the cyclone becoming fairly large toward the end of the 
forecast period.  The NHC forecast wind radii is larger than the 
previous one, trending toward the radii consensus aid.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0300Z 12.1N  23.2W   30 KT  35 MPH
 12H  01/1200Z 12.6N  25.9W   40 KT  45 MPH
 24H  02/0000Z 12.8N  29.2W   50 KT  60 MPH
 36H  02/1200Z 13.2N  32.1W   60 KT  70 MPH
 48H  03/0000Z 13.8N  35.1W   70 KT  80 MPH
 60H  03/1200Z 14.5N  37.5W   80 KT  90 MPH
 72H  04/0000Z 15.4N  40.1W   85 KT 100 MPH
 96H  05/0000Z 18.0N  44.5W   90 KT 105 MPH
120H  06/0000Z 20.7N  47.9W   95 KT 110 MPH
 
$$
Forecaster Cangialosi
 
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