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Tropical Storm Arthur Discussion Number 8
NWS National Hurricane Center Miami FL AL012020
1100 AM EDT Mon May 18 2020
Arthur has become a little better organized this morning with an
overall increase in convection and banding noted since overnight.
The first couple of reconnaissance aircraft passes through the
center have shown that the pressure has fallen to around 996 mb.
The plane has also reported several believable SFMR winds of 38-43
kt, and the anemometer on buoy 41025 at an elevation of only 4 m
has reported a peak 1-minute wind of 37 kt. Based on these data
the initial intensity is set at 45 kt.
The forward speed of Arthur has continued to increase and the
estimated motion is north-northeast at 14 kt. The cyclone should
turn northeastward later today and begin moving away from the North
Carolina Outer Banks as a mid-latitude trough approaches from the
west. By Tuesday, Arthur is forecast to turn eastward within the
mid-latitude westerlies. After that time, a deepening trough over
the central and western Atlantic is expected to cause the cyclone to
turn southeastward as the steering flow turns northwestward. The GFS
and ECMWF are now in relatively good agreement on this scenario and
the new NHC track forecast lies between those typically reliable
models and the multi-model consensus aids.
Although the vertical shear is increasing over the storm and it is
soon moving over cooler waters, some strengthening due to baroclinic
process is predicted over the next 24 hours. The storm should merge
with a frontal boundary late tonight or early Tuesday which will
complete Arthur's transition to an extratropical cyclone. By
Wednesday, the post-tropical cyclone should begin to weaken as the
frontal gradients decrease. The post-tropical cyclone should
dissipate in about 96 h.
1. A Tropical Storm Warning is in effect for a portion of the
North Carolina coast. Tropical-storm-force winds and heavy rains
are expected there today.
2. Dangerous coastal surf conditions and rip currents are expected
to spread northward along the southeast U.S. coast to the
mid-Atlantic states during the next couple of days. See products
from your local National Weather Service Forecast Office for more
FORECAST POSITIONS AND MAX WINDS
INIT 18/1500Z 35.1N 75.2W 45 KT 50 MPH
12H 19/0000Z 36.4N 73.3W 50 KT 60 MPH
24H 19/1200Z 37.2N 70.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
36H 20/0000Z 36.8N 67.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 20/1200Z 35.5N 65.8W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 21/0000Z 34.0N 65.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 21/1200Z 32.0N 64.0W 30 KT 35 MPH...POST-TROP/REMNT LOW