[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 141456
TCDAT5

Subtropical Storm Don Discussion Number   2
NWS National Hurricane Center Miami FL       AL052023
1100 AM AST Fri Jul 14 2023

Don's deep convection has been waning in intensity since the
overnight hours, with most of the activity located in broken bands
to the north and east of the center of circulation.  The cyclone
remains subtropical, given that it is embedded within a deep-layer
trough and has a relatively large radius of maximum winds.  A
just-received ASCAT pass over Don shows a swath of 35-40 kt winds
to the east of the center, so the initial intensity is therefore
lowered to 40 kt.

Don's recent motion has been north-northwestward, or 340/6 kt, with
the cyclone surrounded by a pair of strong mid-level ridges to its
east and north, and a broad trough over the western Atlantic.  The
ridge to the east will be the main steering influence, and that
feature is expected to migrate westward across the Atlantic during
the next several days.  Don is forecast to move slowly around the
northern side of the ridge, turning northward, eastward, and then
southeastward over the next 5 days.  In spite of the somewhat
complicated mid-latitude pattern, the track models are in fairly
good agreement for much of the forecast period.  The new NHC track
forecast is nudged northward during the 2- to 4-day part of the
forecast toward the consensus aids but otherwise is very similar to
the forecast from earlier this morning.

Subsiding dry air on the back side of the trough is getting
entrained into Don's circulation, and the storm is over waters of
25-26 degrees Celsius, heading towards waters as cold as 23 degrees
in about 3 days.  Although the trough may be able to continue to
supply some baroclinic energy to Don, the cyclone's maximum winds
are likely to gradually diminish over the next few days given the
less favorable thermodynamic environment.  There is a chance that
Don could lose enough convective organization and become a
post-tropical cyclone at some point during the next few days.
However, by days 4 and 5, Don will be heading back southward toward
relatively warmer waters, and a new mid-latitude shortwave trough
may provide a boost to the system's organization and strength.  As a
result, the NHC intensity forecast shows possible restrengthening at
the end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 33.7N  47.3W   40 KT  45 MPH
 12H  15/0000Z 34.5N  47.5W   40 KT  45 MPH
 24H  15/1200Z 36.0N  47.8W   40 KT  45 MPH
 36H  16/0000Z 37.4N  48.1W   35 KT  40 MPH
 48H  16/1200Z 38.5N  47.7W   35 KT  40 MPH
 60H  17/0000Z 39.0N  46.2W   35 KT  40 MPH
 72H  17/1200Z 38.6N  43.9W   35 KT  40 MPH
 96H  18/1200Z 35.7N  40.0W   35 KT  40 MPH
120H  19/1200Z 33.7N  38.6W   40 KT  45 MPH

$$
Forecaster Berg
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