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Tropical Storm Ophelia Discussion Number   6
NWS National Hurricane Center Miami FL       AL172017
1100 AM AST Tue Oct 10 2017

Convective banding has continued to become better defined since the
previous advisory, and an eye-like feature has developed in the
center of the convection. However, despite the much improved
satellite appearance, it appears that the increased convective
organization has not yet translated into an increase in the surface
winds based on a 1204Z ASCAT-B overpass, which only showed winds of
30-31 kt in the southern quadrant. Some undersampling is likely due
to the small 25-nmi radius of maximum winds, and two nearby ships
were under-sampled by at least 5 kt. Dvorak intensity estimates
range from T2.3/33 kt from UW-CIMSS to T3.0/45 kt from TAFB to
T4.0/65 kt from SAB. For now, the initial intensity will remain at
45 kt, which is an average of the scatterometer winds and all of the
other available intensity estimates.

Ophelia has been lumbering along slowly toward the southeast during
the past 6 hours, and the initial motion estimate is now 130/04 kt.
The latest model guidance remains in excellent agreement on the
cyclone moving slowly toward the southeast for next 48 hours or so.
By 72 hours, Ophelia is expected to turn northeastward and
gradually accelerate into the westerlies ahead of a deep-layer
trough. Since the NHC model guidance is tightly packed about the
previous advisory track, only minor adjustments were made for this
advisory.

The intensity forecast isn't as straightforward as the track
forecast due to the aforementioned differences in the intensity
estimates. However, given that both the GFS and ECMWF models
accurately predicted much lower intensity values of 35-40 kt for
the 1200Z initial time period, a blend of those models were used to
construct the intensity forecast for this advisory package. In
addition to the slightly lower intensity forecast, the wind radii
were also decreased both at the initial time and throughout the
forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 31.5N  38.3W   45 KT  50 MPH
 12H  11/0000Z 30.9N  37.9W   50 KT  60 MPH
 24H  11/1200Z 30.2N  37.4W   55 KT  65 MPH
 36H  12/0000Z 29.8N  36.9W   60 KT  70 MPH
 48H  12/1200Z 30.0N  36.2W   65 KT  75 MPH
 72H  13/1200Z 31.2N  33.8W   70 KT  80 MPH
 96H  14/1200Z 33.4N  28.5W   70 KT  80 MPH
120H  15/1200Z 36.0N  21.5W   70 KT  80 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

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