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Thursday, July 3, 2014

HURRICANE ARTHUR STRENGTHENS; TRACKS SLIGHTLY WEST / CAT 2 STATUS UPDATE


HURRICANE ARTHUR DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012014
500 PM EDT THU JUL 03 2014

The eye of Arthur has become more distinct in visible satellite
imagery this afternoon, although the overall radar presentation has
changed very little. The latest flight-level and SFMR wind
observations are 84 kt and 82 kt respectively.  These data support
maintaining the 80-kt initial intensity. Environmental conditions
are expected to remain conducive for strengthening during the next
12 to 18 hours and Arthur is still forecast to reach category two
intensity as it nears the North Carolina coast.  Vertical shear is
forecast to increase significantly by Friday night and weakening
should commence by that time.  Arthur is expected to interact with
an approaching deep-layer trough and should become a post-tropical
cyclone within 48 hours. Steady weakening is anticipated after
Arthur becomes post-tropical.

Aircraft and radar fixes indicate that the initial motion is 020
degrees at 11 kt, a little faster than before.  Arthur is expected
to turn northeastward and accelerate ahead of a deep-layer trough
that will move into the eastern United States during the next day
or so.  Although the models still remain in good agreement on the
track of Arthur during the next couple of days, there has been a
westward shift this cycle.  The new NHC track has been shifted
westward and lies between the GFS and ECMWF models through 36
hours.  The updated track now shows landfall in eastern North
Carolina or the Outer Banks later tonight.   Beyond 36 hours, the
NHC track has been adjusted about a degree westward, but it is not
as far west as the GFS and ECMWF model trackers.

While in most cases this westward shift in the track will be
immaterial to impacts, it does mean that the hurricane's strongest
winds are now more likely to be experienced along the Outer Banks,
rather than remain offshore.

NHC public advisories will be issued every two hours beginning at 7
pm EDT this evening and Tropical Cyclone Updates will be issued
on the hour between each Public Advisory to provide hourly position
updates.

The new experimental potential storm surge flooding map is
available at: www.nhc.noaa.gov/graphics_at1.shtml?inundation

FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 33.4N  77.9W   80 KT  90 MPH
 12H  04/0600Z 35.3N  76.1W   85 KT 100 MPH
 24H  04/1800Z 38.2N  72.6W   85 KT 100 MPH
 36H  05/0600Z 41.9N  68.0W   75 KT  85 MPH
 48H  05/1800Z 45.2N  64.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  06/1800Z 50.4N  56.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  07/1800Z 56.5N  47.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  08/1800Z 60.0N  37.5W   30 KT  35 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown