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Subtropical Depression Don Discussion Number  12
NWS National Hurricane Center Miami FL       AL052023
1100 PM AST Sun Jul 16 2023
 
Convection has been waxing and waning near Don this evening, with
only a small area of -50 to -60C tops occuring to the east of the
center. Despite the relatively meager convective structure, Don's
appearance now looks more akin to a sheared tropical depression,
since the upper-level low that was over Don at the start of the
weekend has largely dissipated. However, the most recent TAFB Dvorak
classification kept the system subtropical given the limited
convective activity, and so Don will still be classified as a
subtropical cyclone at this time, with maximum sustained winds
of 30 kt for this advisory.
 
Don continues to move eastward, with the latest motion estimated at 
090/9 kt. An anomalously strong low- to mid-level anticyclone is 
currently centered south of Don, and this feature is expected to 
shift westward and quickly build poleward to the west and northwest 
of the cyclone. Eventually this ridge will fold back over to Don's 
north towards the end of this week. The net result of this pattern 
reconfiguration is Don should begin to execute a clockwise loop over 
the Central Atlantic, first turning southeast tomorrow, south and 
southwest by Tuesday, and finally turning westward and then 
northwestward towards the middle to latter part of the week. The 
track guidance this cycle has shifted back eastward, and only modest 
track adjustments were needed in the official forecast for the first 
three days, followed by an adjustment eastward in days 4-5. However, 
given the continued spread in the ensemble track guidance at that 
time range, that portion of the forecast remains low confidence.
 
Don’s short-term future is dependent on its ability to continue 
producing enough convective activity to prevent it from becoming a 
remnant low. Right now, sea-surface temperatures over the system are 
around 23C, about the coldest they will be along its forecast track. 
As the system begins to lose latitude over the next several days, 
these waters warm to around 25C, while upper-level temperatures 
remain sufficently cold to result in increased instability. Both the 
regional-hurricane models and global models show Don maintaining or 
increasing convective activity near its center as it moves 
southward. For these reasons, the latest intensity forecast now 
shows the system transitioning to a tropical cyclone a bit earlier, 
and also shows some gradual intensification beginning at 48 hours as 
the system moves over these warmer waters. A bit more 
intensification is shown in the latter part of the forecast, but 
still remains under the majority of the guidance in the extended 
range given the larger-than-normal uncertainty in the location and 
structure of the system at the end of the forecast period.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/0300Z 39.4N  45.8W   30 KT  35 MPH
 12H  17/1200Z 39.1N  43.9W   30 KT  35 MPH
 24H  18/0000Z 37.9N  41.8W   30 KT  35 MPH
 36H  18/1200Z 36.3N  40.7W   30 KT  35 MPH...TROPICAL CYCLONE
 48H  19/0000Z 34.6N  40.5W   35 KT  40 MPH
 60H  19/1200Z 33.5N  40.9W   35 KT  40 MPH
 72H  20/0000Z 33.2N  41.7W   40 KT  45 MPH
 96H  21/0000Z 34.2N  44.6W   40 KT  45 MPH
120H  22/0000Z 37.2N  48.1W   40 KT  45 MPH
 
$$
Forecaster Papin
 
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