[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 142045
TCDAT5

Subtropical Storm Don Discussion Number   3
NWS National Hurricane Center Miami FL       AL052023
500 PM AST Fri Jul 14 2023

Don is producing two broken bands of convection which are displaced
to the east of the low-level center.  The cyclone still leans
heavily on the subtropical side of the spectrum, lacking a central
dense overcast, being associated with an upper-level low, and having
an asymmetric distribution of convection.  However, this morning's
ASCAT data did indicate that the radius of maximum winds had
contracted down to 30 n mi, more akin to a tropical cyclone.  Based
on the earlier ASCAT data and an Hebert-Poteat classification of
ST2.5 from TAFB, the initial intensity remains 40 kt.

Don deviated to the left of the previous forecast track during the
past few hours and is estimated to be moving northwestward, or
325/7 kt.  Despite that, the track forecast reasoning is unchanged.
An eastern Atlantic mid-level ridge will be the main steering
influence and is expected to migrate westward across the Atlantic
during the next several days.  Don is forecast to move around the
northern and eastern side of the ridge, turning northward,
eastward, and then southward over the next 5 days.  The new NHC
track forecast has been shifted a bit westward, mainly due to the
recent deviation to the west, and is close to a blend of the TVCA
and FSSE consensus aids.

Subsidence behind the trough is causing dry air to be entrained
into Don's circulation, and the storm is currently over waters of
25-26 degrees Celsius.  The forecast track takes Don over waters as
cold as 23 degrees in about 3 days, and simulated satellite imagery
from the GFS and ECMWF suggests that the convective coverage
and pattern could be quite degraded by that time.  Still, the
intensity guidance is in relatively good agreement that Don will
only weaken a bit during the next several days, with some possible
restrengthening by the end of the forecast period when the storm
again reaches warmer waters.  For continuity's sake, the forecast
continues to show Don maintaining subtropical storm status for the
next 5 days, but it could become post-tropical at any time if the
convection wanes and loses organization.


FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 34.1N  48.0W   40 KT  45 MPH
 12H  15/0600Z 35.1N  48.3W   40 KT  45 MPH
 24H  15/1800Z 36.5N  48.7W   40 KT  45 MPH
 36H  16/0600Z 37.8N  48.6W   35 KT  40 MPH
 48H  16/1800Z 38.7N  47.7W   35 KT  40 MPH
 60H  17/0600Z 38.7N  45.8W   35 KT  40 MPH
 72H  17/1800Z 37.9N  43.7W   35 KT  40 MPH
 96H  18/1800Z 35.0N  40.7W   35 KT  40 MPH
120H  19/1800Z 33.0N  40.6W   40 KT  45 MPH

$$
Forecaster Berg
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