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Tropical Storm Don Discussion Number  30
NWS National Hurricane Center Miami FL       AL052023
1100 AM AST Fri Jul 21 2023
 
Shortly after the release of the previous advisory convection 
nearly wrapped completely around the center of Don.  Since the 
time, the convection has become somewhat more fragmented, but there 
is still a well-defined curved band that wraps about three-quarters 
of the way around Don's center.  Subjective Dvorak T-numbers from 
SAB and TAFB are a unanimous T3.0 or 45 kt, so the initial 
intensity remains 45 kt for this advisory.  A recently arriving 
scatterometer overpass missed the core of the cyclone so there is 
no information on the system's strength from that data source 
this morning. 

The initial motion estimate is still west-northwestward or 300 
degrees at 9 kt.  A low- to mid-level ridge to the north-northeast 
of the cyclone is forecast to shift eastward during the next 24 to 
36 hours causing Don to turn northwestward, and then northward 
during the next day or two.  After that time, Don is expected to 
turn northeastward within low- to mid-level southwesterly flow 
between the ridge and a broad trough over eastern Canada and the 
northeastern United States.  The dynamical models are tightly 
clustered and little overall change was made to the previous NHC 
track forecast. 

Don remains over marginally warm sea surface temperatures and 
within a relatively dry mid-level environment so little overall 
change in strength is predicted during the next 12 to 24 hours.  
The system is forecast to pass over the slightly warm waters of 
the Gulf stream on Saturday, but this is not likely to result in a 
significant change in strength.  By Sunday morning, Don will have 
moved north of the Gulf stream and over much colder SSTs.  This 
should result in weakening and the system's transition into a 
post-tropical cyclone.  Dissipation is predicted by the global 
models in a little more than 3 days, and the official forecast 
follows suit. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  21/1500Z 35.8N  46.5W   45 KT  50 MPH
 12H  22/0000Z 36.9N  48.0W   45 KT  50 MPH
 24H  22/1200Z 38.8N  49.9W   45 KT  50 MPH
 36H  23/0000Z 41.1N  50.9W   45 KT  50 MPH
 48H  23/1200Z 43.7N  50.6W   40 KT  45 MPH
 60H  24/0000Z 46.1N  49.1W   35 KT  40 MPH...POST-TROPICAL
 72H  24/1200Z 48.4N  45.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  25/1200Z...DISSIPATED
 
$$
Forecaster Brown
 
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