[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 211445
TCDAT5

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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