[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 152042
TCDAT2

Hurricane Ophelia Discussion Number  27
NWS National Hurricane Center Miami FL       AL172017
500 PM AST Sun Oct 15 2017

Ophelia's cloud structure is declining rapidly, and microwave and
shortwave IR imagery indicate that the low-level and mid-level
centers are becoming separated.  However, some deep convection is
still present near Ophelia's center, and an SSMIS pass from 1827 UTC
indicated that the hurricane still has an inner core that is
separated from a front to the north and west.  The estimated maximum
winds have been decreased slightly to 75 kt given the overall decay
of the cloud structure.  However, the cyclone's favorable position
relative to an upper-level jet streak is likely contributing to
deepening of the low as the wind field expands substantially.  Only
a slight decrease in the maximum winds is therefore expected before
the post-tropical cyclone reaches Ireland.  After that time,
interaction with land while the cyclone occludes should cause it to
weaken more rapidly.  Around 48 h, the cyclone's circulation is
likely to become ill-defined and dissipate near the western coast of
Scandinavia.

Ophelia has continued to move toward the north-northeast, and the
initial motion estimate remains 025/33 kt.  There has been no change
to the track forecast reasoning since Ophelia is already embedded
within the flow associated with a large mid-latitude trough.  This
should keep Ophelia on a north-northeast heading as it passes over
Ireland and the UK on Monday.  The dynamical guidance remains in
very good agreement on the track of Ophelia, and very little change
has been made to the track forecast.

Since Ophelia will be post-tropical as it approaches Ireland and the
UK, strong winds and rain will arrive over land areas sooner than
the center. For more information on local impacts, consult products
from local meteorological services in Ireland and the United Kingdom
for more information.

KEY MESSAGES:

1. Ophelia is expected to be a powerful extratropical cyclone with
hurricane force winds while it moves near Ireland and the United
Kingdom.  Direct impacts from wind and heavy rain in portions of
these areas are likely, along with dangerous marine conditions. For
more details on the magnitude, timing, and location of impacts from
post-tropical Ophelia, residents in Ireland should refer to products
issued by Met Eireann, and residents in the United Kingdom should
refer to products issued by the Met Office.

2. Individuals are urged to not focus on the exact track of Ophelia
since strong winds and heavy rainfall will extend well outside of
the NHC forecast cone.


FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 44.6N  13.3W   75 KT  85 MPH
 12H  16/0600Z 49.2N  11.3W   70 KT  80 MPH...POST-TROP/EXTRATROP
 24H  16/1800Z 54.3N   7.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 36H  17/0600Z 58.5N   2.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  17/1800Z...DISSIPATED

$$
Forecaster Zelinsky
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