Subtropical Depression DON (Text)

Subtropical Depression Don Discussion Number  10
NWS National Hurricane Center Miami FL       AL052023
1100 AM AST Sun Jul 16 2023
Satellite images indicate that Don is producing a small area of
convection in the southeastern quadrant, though it is stretch to
call it very organized.  Overall, the system is mostly a big swirl
of low- to mid-level clouds with occasional bursts of modest
convection.  A 1250 UTC ASCAT-B scatterometer pass showed maximum 
winds of about 30 kt, so that will be the initial wind speed. 
Don has turned to the east-northeast this morning, and should
gradually execute a large clockwise loop over the central Atlantic
during the next few days, turning southeast, south and southwest. 
Model guidance is in good agreement on this course through midweek, 
and little change was made to the previous forecast.  The long 
range forecast is more uncertain, however, with Don potentially 
becoming trapped in an area of lighter steering currents before 
moving more northward, rather than westward in the loop.  The model 
spread is enormous by day 5, with about 1000 n mi of distance 
between some of the ECMWF ensemble members.  The new forecast is 
trended westward toward the multi-model ensemble mean, with a 
majority suggesting a northwest track at the end of the forecast 
period, but that's far from certain.
The environment near Don is expected to be pretty hostile for the 
next few days, with any cold air aloft promoting convection being 
neutralized by cool waters, dry air surrounding the cyclone, and 
some shear.  This should result in little intensity change during 
the next few days, and Don could also degenerate into a remnant low, 
especially tomorrow when conditions could be the most harsh.  At 
long range, Don might have a chance to re-strengthen since it moves 
over warmer waters with more instability, but Don could also be too 
weak to take advantage of these factors.  Considering the large 
track uncertainty, the new forecast is the same as the previous one 
at long range, below the model guidance.
INIT  16/1500Z 39.0N  48.1W   30 KT  35 MPH
 12H  17/0000Z 39.4N  46.8W   30 KT  35 MPH
 24H  17/1200Z 38.9N  44.6W   30 KT  35 MPH
 36H  18/0000Z 37.8N  42.5W   30 KT  35 MPH
 48H  18/1200Z 36.2N  41.2W   30 KT  35 MPH
 60H  19/0000Z 34.7N  41.2W   30 KT  35 MPH
 72H  19/1200Z 33.5N  41.8W   30 KT  35 MPH
 96H  20/1200Z 33.0N  43.6W   35 KT  40 MPH
120H  21/1200Z 35.0N  47.0W   35 KT  40 MPH
Forecaster Blake

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Page last modified: Monday, 18-Dec-2023 12:09:11 UTC