[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 232031
TCDAT5

Tropical Storm Don Discussion Number  39
NWS National Hurricane Center Miami FL       AL052023
500 PM AST Sun Jul 23 2023

Tropical Storm Don is moving northeastward this afternoon over the
North Atlantic's cooler sea surface temperatures, and deep
convection is starting to wane. The convective band from earlier
this morning has become more fragmented and not as well defined.
Visible satellite and a microwave AMSR2 pass earlier however, still
showed that Don has a compact low-level center, and a scatterometer
ASCAT-B pass showed winds of 48-50 kt in the southeast quadrant.
Subjective Dvorak estimates from TAFB and SAB have also started to
trend downward with this advisory cycle. Given the ASCAT-B pass and
the subjective satellite estimates, the initial intensity for this
advisory is lowered to 50 kt.

Don is starting to lose its overall convective pattern and should
begin to rapidly weaken tonight and tomorrow. Available global
model guidance suggest that Don should lose any remaining deep
convection within the next 18 to 24 hours and become a post-tropical
cyclone at that time.  The intensity forecast remains similar to
the previous forecast, with Don dissipating in about 48 hours.

The system is moving to the northeast at 15 kt.  Don will continue
to move to the northeast, with a slight increase in forward speed
the remainder of today, before turning to the east-northeast
tomorrow due to the steering flow around the northern side of the
subtropical ridge.  Guidance remains tightly clustered, and there
was very little change to the forecast this cycle.

The storm is moving up the list of longest-lasting tropical cyclones
on record for July (including subtropical stages). Preliminary,
Don is tied for 10th, and the cyclone could make the top 5
longest-lasting for July if it lasts through early Monday.


FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 45.2N  46.5W   50 KT  60 MPH
 12H  24/0600Z 46.6N  44.1W   40 KT  45 MPH
 24H  24/1800Z 47.9N  39.8W   30 KT  35 MPH...POST-TROPICAL
 36H  25/0600Z 48.8N  34.7W   30 KT  35 MPH...POST-TROPICAL
 48H  25/1800Z...DISSIPATED

$$
Forecaster Kelly/Pasch
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