Tropical Storm Arthur Discussion Number   9
NWS National Hurricane Center Miami FL       AL012020
500 PM EDT Mon May 18 2020

Although the center of Arthur did not make landfall in the North 
Carolina Outer Banks, it passed within about 20 n mi southeast of 
Cape Hatteras around 1500 UTC.  Tropical-storm-force wind gusts have 
been reported at several automated observing sites on and near the 
Outer Banks, with the highest sustained wind of 34 kt at Alligator 
River Bridge earlier this afternoon.  Deep convection continues over 
the northeastern portion of Arthur's circulation, but visible 
imagery has recently shown an increase in separation between 
low-level center and the convective activity.  This is the result of 
increasing southwesterly shear and the beginning of the cyclone's 
extratropical transition.  The initial intensity remains 45 kt, 
which was in agreement with the earlier aircraft data.  As the 
cyclone completes its extratropical transition, some strengthening 
is forecast due to baroclinic processes.  After 24 hours, little 
change in strength is expected until the frontal gradients decrease 
on Wednesday.  The system should gradually spin down after that 
time, and dissipate by late in the week.

The initial motion estimate is 045/14 kt.  Arthur should continue 
northeastward this evening, but is expected to turn eastward Tuesday 
morning as the cyclone becomes embedded within the mid-latitude 
westerlies.  Troughing over the central and western Atlantic should 
cause the Arthur to turn southeastward on Wednesday when the 
steering flow becomes northwesterly.  Little change was required to 
the previous NHC official forecast and the updated track again lies 
between the GFS, ECMWF, and the multi-model consensus. 

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  18/2100Z 36.1N  73.9W   45 KT  50 MPH
12H  19/0600Z 36.9N  71.6W   50 KT  60 MPH
24H  19/1800Z 37.0N  68.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
36H  20/0600Z 36.2N  66.8W   50 KT  60 MPH...POST-TROP/EXTRATROP
48H  20/1800Z 34.8N  65.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
60H  21/0600Z 33.0N  64.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
72H  21/1800Z 31.5N  64.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
96H  22/1800Z...DISSIPATED

$$
Forecaster Brown