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Subtropical Storm Don Discussion Number   1
NWS National Hurricane Center Miami FL       AL052023
500 AM AST Fri Jul 14 2023

The area of low pressure that NHC has been monitoring roughly midway 
between Bermuda and the Azores has become Subtropical Storm Don.  
The storm is assessed as subtropical because it is embedded within 
an upper-level trough and has a relatively large radius of maximum 
wind.  Several hours ago, a well-defined center of circulation 
developed and deep convection has remained sufficiently organized, 
especially in bands to the east of the center.  A pair of partial 
ASCAT passes from around 00Z showed peak winds around 45 kt, and 
that is the initial intensity set for this advisory.

Don has been moving slowly northward at about 5 kt during the past 6 
to 12 hours, and a continued slow northward or north-northwestward 
motion is expected during the next couple of days as a building 
ridge over the central Atlantic prevents it from accelerating 
poleward.  That ridge is expected to weaken on Sunday while another 
ridge builds to the southeast of Don and a trough amplifies over the 
northeastern Atlantic.  This pattern change should cause Don to turn 
eastward on Sunday and then southeastward early next week.  The NHC 
track forecast lies near the middle of the guidance envelope, in 
best agreement with the various consensus aids.

The storm is likely near its peak intensity already.  Dry air is 
wrapping in on the south and west sides of the circulation and that 
stable air is expected to continue to entrain into the storm during 
the next several days.  In addition, sea surface temperatures are 
expected to decrease along the forecast track during the next 2 or 
3 days.  Although the environment is not conducive for 
strengthening, it is also not hostile enough to cause significant 
weakening.  Therefore, the NHC official forecast shows a gradual 
decay in Don’s strength.  The environment looks more conducive by 
the end of the period, and some strengthening is possible by then 
if the storm survives that long.  The NHC intensity forecast 
follows the theme of the models, which are tightly clustered.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  14/0900Z 32.9N  46.8W   45 KT  50 MPH
 12H  14/1800Z 33.5N  47.0W   45 KT  50 MPH
 24H  15/0600Z 34.9N  47.3W   45 KT  50 MPH
 36H  15/1800Z 36.4N  47.8W   45 KT  50 MPH
 48H  16/0600Z 37.6N  47.8W   40 KT  45 MPH
 60H  16/1800Z 38.4N  47.1W   40 KT  45 MPH
 72H  17/0600Z 38.5N  44.9W   35 KT  40 MPH
 96H  18/0600Z 35.9N  40.7W   35 KT  40 MPH
120H  19/0600Z 33.4N  38.5W   40 KT  45 MPH
 
$$
Forecaster Cangialosi
 
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