Hurricane OPHELIA (Text)


Hurricane Ophelia Discussion Number  14
NWS National Hurricane Center Miami FL       AL172017
1100 AM AST Thu Oct 12 2017

Ophelia's satellite presentation consists of a distinct eye in
infrared imagery surrounded by a ring of cloud tops of -50C to -70C.
The initial intensity of 80 kt is based on a blend of the latest
subjective and objective Dvorak estimates, which range from 77 to
95 kt.  Little change in intensity is expected during the next 48
hours, as Ophelia will remain over SSTs of 25-26C and in a low
to moderate shear environment.  After that time, the cyclone should
begin extratropical transition as it interacts with a potent
mid-latitude trough moving eastward across the north Atlantic. This
baroclinic interaction should maintain Ophelia at hurricane
intensity through 96 hours, with slow weakening expected after that
time as the extratropical cyclone occludes.

Ophelia has moved little since the last advisory, with the cyclone
currently situated south of the mid-latitude westerlies.  The
initial motion estimate is a slow north-northeastward drift at
around 2 kt.  A steadier northeastward motion should begin by 12 h
when the aforementioned upper-level trough begins to exert influence
on Ophelia's motion.  An east-northeastward acceleration is expected
at 24 through 48 h, followed by a turn back to the northeast and
north-northeast at days 3 through 5 as Ophelia interacts with the
southern portion of the trough.  Through the first 48 hours, the new
NHC track forecast is similar to the previous one and lies near the
middle of the guidance envelope.  Later in the forecast period,
there remains a fair bit of east/west spread in the track of Ophelia
near Ireland and the United Kingdom, which isn't usual at these time
ranges.   The NHC forecast at these times is similar to the previous
one and lies on the right side of the deterministic guidance
envelope but is near the middle of the ECMWF, UKMET and GEFS
ensemble members.  Regardless of the exact track, post-tropical
Ophelia is likely to bring some impacts to Ireland and the United
Kingdom as a powerful extratropical cyclone in 4 to 5 days.

While the track guidance keeps the center of Ophelia east of the
Azores, a tropical storm watch or warning could be needed for the
eastern Azores later today or tonight because of the expected
increase in the size of the tropical-storm-force winds in the
northwestern quadrant of the cyclone.


1. Ophelia is expected to transition to a hurricane-force post-
tropical cyclone by Monday when it moves near Ireland and the
United Kingdom.  While post-tropical Ophelia will likely bring some
direct impacts from wind and heavy rain to portions of these areas,
as well as dangerous marine conditions, given the forecast
uncertainty at these time ranges it is too soon to determine the
exact magnitude, timing and location of the impacts.  Residents in
Ireland and the United Kingdom should monitor the progress of
Ophelia for the next several days.  For more information on local
impacts, residents of Ireland should refer to products issued by Met
Eireann and residents in the United Kingdom should refer to products
issued by the Met Office.


INIT  12/1500Z 30.5N  35.6W   80 KT  90 MPH
 12H  13/0000Z 30.9N  34.9W   80 KT  90 MPH
 24H  13/1200Z 31.6N  33.4W   80 KT  90 MPH
 36H  14/0000Z 32.7N  30.8W   75 KT  85 MPH
 48H  14/1200Z 34.4N  27.3W   75 KT  85 MPH
 72H  15/1200Z 40.9N  18.8W   75 KT  85 MPH
 96H  16/1200Z 51.0N  12.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  17/1200Z 60.5N   5.5W   55 KT  65 MPH...POST-TROP/EXTRATROP

Forecaster Brennan


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Page last modified: Sunday, 31-Dec-2017 12:09:53 UTC