Tropical Storm Arthur Forecast Discussion Number 7

By | May 18, 2020

Issued at 500 AM EDT Mon May 18 2020


000
WTNT41 KNHC 180835
TCDAT1
 
Tropical Storm Arthur Discussion Number   7
NWS National Hurricane Center Miami FL       AL012020
500 AM EDT Mon May 18 2020
 
Arthur remains poorly organized in both satellite and radar imagery 
this morning, with the low-level center located near the 
southwestern edge of a complex of ragged convective bands.  Surface 
observations from buoys off of the North Carolina coast suggest the 
central pressure has fallen a little since the last aircraft fix, 
so the intensity will be held at 40 kt for this advisory.  The next 
aircraft is scheduled to reach Arthur between 11-12Z. 

Arthur's forward speed has increased with the initial motion now 
020/12.  A baroclinic trough and associated surface front 
approaching from the west should cause Arthur to turn northeastward 
during the next several hours, with the forecast track showing the 
center passing near or just offshore of the North Carolina Outer 
Banks.  By Tuesday and Tuesday night, Arthur will be entering the 
strong mid-latitude Westerlies, which will steer cyclone eastward 
for a day or two.  After that time, Arthur or its remnants should 
turn southeastward and southward on the southwest side of a 
deep-layer trough over the central Atlantic.  The latest guidance 
is showing a more southward motion after 60 h than seen previously, 
and the new forecast track is also nudged southward during that 
time.

Arthur is moving near and almost parallel to the Gulf Stream, and 
the warm water could allow some strengthening before southwesterly 
shear increases significantly later today.  The cyclone should merge 
with a frontal system and become extratropical in the 24-36 h 
period, with the global models indicating some increase in the winds 
north of the center as this occurs.  The intensity forecast calls 
for Arthur to reach a 50 kt intensity in 36 h as an extratropical 
low in best agreement with the GFS model.  After 48 h, the system 
should decay, and the global models suggest it should dissipate in 
the 96-120 h period.  The new intensity forecast has only minor 
tweaks from the previous forecast.
 
 
Key Messages:
 
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
details.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/0900Z 33.5N  76.6W   40 KT  45 MPH
 12H  18/1800Z 35.2N  74.9W   45 KT  50 MPH
 24H  19/0600Z 36.5N  72.1W   45 KT  50 MPH
 36H  19/1800Z 36.5N  69.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  20/0600Z 35.6N  66.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 60H  20/1800Z 34.4N  65.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  21/0600Z 33.0N  64.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  22/0600Z 31.0N  63.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
120H  23/0600Z...DISSIPATED
 
$$
Forecaster Beven
 

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