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Tropical Storm ARTHUR

Tropical Storm Arthur Discussion Number  10
NWS National Hurricane Center Miami FL       AL012020
1100 PM EDT Mon May 18 2020
Arthur's cloud shield has shifted to the left or north side of the
cyclone's direction of motion since the previous advisory, which is
a distinctive sign of a tropical cyclone beginning to lose its
tropical characteristics, especially now due to the cyclone moving
over 23 deg C sea-surface temperatures. However, there remains
enough convection within 45-75 nmi of the center for Arthur to still
be classified as a tropical cyclone. The initial intensity has been 
increased to 50 kt based on a recent 0129 UTC ASCAT-B overpass that 
indicated several 50-51 kt wind vectors existed in the northwestern
The initial motion estimate is 070/13 kt.  Arthur should move east-
northeastward tonight and then turn toward the east by Tuesday
morning as the cyclone moves around the northern periphery of a
low- to mid-level ridge. On day 2, all of the global models are
forecasting the mid- and upper-level circulations to separate
from the low-level circulation, with the latter feature dropping
southeastward and then southward around the eastern portion of a
low-level ridge. The new track forecast is similar to but slightly
east of the previous advisory track on days 2 and 3, and closely
follows a blend of the consensus models TVCN and GFEX.
Only slight strengthening is expected during the next day or so
due to baroclinic effects while Arthur undergoes extratropical
transition. Data from NOAA Buoy 44014, located west Arthur's
center, indicate that a cold front passed over that station around
2300 UTC, which would place the front about 50-75 nmi west of the
cyclone at this time. Therefore, a merger with the front is likely
during the next 12 hours. The system should begin to steadily
weaken shortly after 24 hours when Arthur will be moving over
SSTs near 20 deg C, and in conjunction with the aforementioned
decoupling of the circulations.
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.
INIT  19/0300Z 36.4N  72.4W   50 KT  60 MPH
 12H  19/1200Z 36.9N  70.1W   55 KT  65 MPH...POST-TROP/EXTRATROP
 24H  20/0000Z 36.4N  67.3W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  20/1200Z 35.2N  65.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  21/0000Z 33.7N  64.6W   40 KT  45 MPH...POST-TROP/EXTRATROP
 60H  21/1200Z 32.3N  64.4W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  22/0000Z 30.9N  64.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  23/0000Z...DISSIPATED
Forecaster Stewart