[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 192047
TCDAT5

Tropical Storm Don Discussion Number  23
NWS National Hurricane Center Miami FL       AL052023
900 PM GMT Wed Jul 19 2023

Don has continued to become better organized during the day, with a
deep convective band now curving more than halfway around the
center, and an expanding outflow pattern especially southeast of
the storm.  While the western side of the circulation still has a
lot of dry air lurking, it seems like the lack of shear is allowing
the core of the cyclone to develop.  Dvorak estimates have
increased, and a blend of the latest data gives an initial wind
speed of 40 kt.  Scatterometer has missed the core for about the
past day, so hopefully tonight's passes will validate the improving
satellite presentation.

Further intensification is likely for the next day or so while Don
moves over a local maximum in sea-surface temperatures (SSTs) with
light shear.  Thereafter, the environment becomes less conducive
with cooling SSTs, drier environmental air, and perhaps an increase
in shear.  The forecast is kept steady through the end of the work
week, then some weakening while Don crosses its own cool wake.  The
NHC wind speed prediction is bumped up from the last one, consistent
with the latest model consensus, and most of the guidance is in
pretty good agreement on this scenario.  The storm should lose all
of its deep convection and become post-tropical late Sunday or on
Monday after it crosses north of the Gulf Stream.

Don has turned westward, now moving a bit faster at 7 kt.  The
system should turn west-northwestward tomorrow as it moves beneath a
large blocking ridge over the north-central Atlantic, with no
changes to the forecast in the short term.  However, there has been
a pretty significant synoptic pattern shift in the models by Friday
with the blocking ridge much slower to depart, resulting in Don
moving more to the northwest and not accelerating as quickly
northeastward.  The new forecast follows the guidance trend, but for
continuity concerns, the forecast is still faster than most of the
guidance, and further changes will likely be required on the next
advisory.


FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 33.8N  40.3W   40 KT  45 MPH
 12H  20/0600Z 33.7N  41.3W   45 KT  50 MPH
 24H  20/1800Z 34.1N  42.7W   50 KT  60 MPH
 36H  21/0600Z 34.8N  44.3W   50 KT  60 MPH
 48H  21/1800Z 35.9N  46.1W   50 KT  60 MPH
 60H  22/0600Z 37.2N  47.6W   45 KT  50 MPH
 72H  22/1800Z 39.0N  48.6W   45 KT  50 MPH
 96H  23/1800Z 43.0N  48.0W   45 KT  50 MPH
120H  24/1800Z 45.5N  44.0W   35 KT  40 MPH...POST-TROPICAL

$$
Forecaster Blake
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