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Hurricane OSCAR


Hurricane Oscar Discussion Number  12
NWS National Hurricane Center Miami FL       AL162018
500 PM AST Mon Oct 29 2018

The overall cloud pattern of Oscar is somewhat asymmetrical, and
convective banding is limited to the eastern semicircle of the
cyclone. However, recent visible and microwave imagery indicate
that tight eyewall of the hurricane is still very well defined,
despite the 20 kt or more of westerly shear analyzed in SHIPS and
UW-CIMSS diagnostics. It appears that the shear is not having much
of an affect on Oscar's inner-core, and in fact the small eye of the
hurricane has become better defined over the past 6 hours. Recent
objective and subjective intensity estimates support an intensity of
75-80 kt, and given the small radius of maximum winds (RMW) of
Oscar, it seems more appropriate to round up, yielding an estimated
intensity of 80 kt.

All of the dynamical intensity guidance calls for additional
intensification in the short term. Persistent lightning inside the
hurricane's RMW during the past several hours also supports the
notion of additional strengthening, as this signal has been
associated with intensifying hurricanes in the past. By 24 h and
beyond, Oscar will likely level off in intensity and then begin to
weaken while it moves over much cooler SSTs and begins extratropical
transition. Although this process will likely result in a rapid
expansion of Oscar's tropical-storm-force wind field, it should also
cause the maximum winds associated with the cyclone to steadily
decrease through the end of the week. The NHC intensity forecast is
similar to the previous advisory, and generally follows IVCN
through the forecast period.

Oscar's eye has wobbled during the past several hours, but the
hurricane appears to have already begun its expected turn toward the
north. The hurricane is essentially on-track, and no major changes
were required to the NHC track forecast. A large mid-latitude
trough to the west will likely cause Oscar to accelerate
north-northeastward or northeastward beginning by late Tuesday, and
then rapidly move across the northern central Atlantic in that
direction.  The global models are in reasonably good agreement on
the speed and heading of Oscar through day 5, which is somewhat
unusual for a recurving cyclone. The new official track forecast is
based on a blend of the simple and corrected multi-model consensus
aids, and confidence in the track forecast is fairly high.

Although Oscar is not expected to directly affect any land areas,
large swells from Oscar will affect Bermuda through Wednesday.
Please consult products from your local weather office as these
conditions could cause life-threatening surf and rip currents.


INIT  29/2100Z 26.5N  58.5W   80 KT  90 MPH
 12H  30/0600Z 27.8N  58.4W   90 KT 105 MPH
 24H  30/1800Z 29.9N  57.2W   90 KT 105 MPH
 36H  31/0600Z 33.0N  54.3W   85 KT 100 MPH
 48H  31/1800Z 37.3N  50.3W   80 KT  90 MPH
 72H  01/1800Z 46.7N  40.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  02/1800Z 54.0N  25.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  03/1800Z 60.0N  12.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

Forecaster Zelinsky