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Hurricane Ophelia Discussion Number  13
NWS National Hurricane Center Miami FL       AL172017
500 AM AST Thu Oct 12 2017

Satellite imagery indicates that Ophelia continues to gradually
become better organized, with the hurricane maintaining a
well-defined eye and the cloud tops in the eyewall gradually
cooling.  The various subjective and objective satellite intensity
estimates range between 75-90 kt, and based on the previous trend of
the intensity being near the lower end of the estimates, the initial
intensity is kept at a possibly conservative 75 kt.

The initial motion is 040/3.  Ophelia is currently in an area of
light steering currents to the south of the mid-latitude
westerlies.  The large-scale models forecast a deep-layer trough to
amplify over the central and northeastern Atlantic during the
forecast period, which should steer Ophelia northeastward or
east-northeastward at an increasing forward speed for the next few
days.  The track guidance has changed little since the last
advisory, and the new forecast track, which leans toward the HFIP
Corrected Consensus and the Florida State Superensemble, is an
update of the previous forecast.

Ophelia is forecast to remain in a light to moderate shear
environment and over marginal sea surface temperatures for the next
24-36 h, and the intensity forecast shows some strengthening during
this time in agreement with the guidance.  After that, the hurricane
is expected to move over cooler water.  As that happens, though,
interaction with the above-mentioned westerly trough should help
Ophelia keep its intensity.  Extratropical transition should begin
by 72 h, with Ophelia likely to become a hurricane-force baroclinic
low by 96 h.  The guidance is in good agreement that Ophelia should
affect Ireland, northern Ireland and Great Britain between 96-120 h
as a powerful extratropical low.

Although the track guidance keeps the center offshore of the
Azores, a tropical storm watch or warning could be needed for the
eastern Azores on Thursday because of the forecasted increase in
wind radii in the northwestern quadrant of the cyclone.


FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 30.3N  35.6W   75 KT  85 MPH
 12H  12/1800Z 30.7N  35.2W   80 KT  90 MPH
 24H  13/0600Z 31.3N  34.0W   80 KT  90 MPH
 36H  13/1800Z 32.2N  32.0W   75 KT  85 MPH
 48H  14/0600Z 33.7N  28.6W   75 KT  85 MPH
 72H  15/0600Z 38.5N  20.5W   75 KT  85 MPH
 96H  16/0600Z 49.0N  13.5W   70 KT  80 MPH...POST-TROP/EXTRATROP
120H  17/0600Z 59.0N   7.0W   55 KT  65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven

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