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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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