[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 190831
TCDAT1

Tropical Storm Arthur Discussion Number  11
NWS National Hurricane Center Miami FL       AL012020
500 AM EDT Tue May 19 2020

Arthur's cloud pattern has continued to take on a generally
post-tropical appearance, though a recent convective burst near its
center suggests that it isn't quite post-tropical yet. Satellite
imagery and earlier scatterometer data also indicate the presence of
a developing warm front near the cyclone's center, and this could be
contributing the the development of the aforementioned convective
burst. ASCAT-C data that arrived early this morning showed maximum
winds of 45-50 kt, and this was the primary basis for the initial
intensity.

Virtually no change was made to the intensity forecast. Despite the
recent increase of convection near Arthur's center, extratropical
transition should finish fairly soon. Slight strengthening due to
baroclinic forcing is possible through the afternoon, but the
cyclone is forecast to begin spinning down by tonight or Wednesday
morning. The global and regional models indicate that the system
will dissipate within about 72 h, and this is reflected in the
official forecast.

Only small adjustments were made to the track forecast, which
remains near the multi-model consensus. As Arthur weakens it should
be steered generally southward around the east side of a low-level
ridge. The models differ on how quickly the southward turn will
occur, but all agree on that general scenario. The latest NHC
forecast is a little west of the previous one after 24 h.

Dangerous coastal surf conditions and rip currents are expected to
continue along portions of the mid-Atlantic and southeast U.S.
coasts during the next couple of days.  See products from your local
National Weather Service Forecast Office for more details.


FORECAST POSITIONS AND MAX WINDS

INIT  19/0900Z 37.0N  70.6W   50 KT  60 MPH
 12H  19/1800Z 36.9N  68.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 24H  20/0600Z 36.1N  66.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  20/1800Z 34.6N  65.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  21/0600Z 33.3N  65.2W   35 KT  40 MPH...POST-TROP/EXTRATROP
 60H  21/1800Z 32.0N  65.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
 72H  22/0600Z...DISSIPATED

$$
Forecaster Zelinsky
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