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HURRICANE ORLENE DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP162016
200 PM PDT TUE SEP 13 2016

Recent microwave satellite data, including an ASCAT overpass,
confirm that Orlene has become tilted with the low-level center
displaced to the south of the weak eye present in visible imagery.
Based on an average of subjective and objective satellite
intensity estimates, the initial intensity is reduced to 75 kt.

The microwave data indicate that the center of Orlene is farther
south than the position on the previous advisory, and the initial
motion estimate is now 015/2 kt. Orlene is now within a break in
the subtropical ridge caused a mid- to upper-level trough over
California and the adjacent waters.  The dynamical models forecast
the trough to move eastward during the next 24-36 hours, with the
ridge rebuilding to the north of the tropical cyclone.  This
evolution should produce a slow motion for the next 12-24 hours,
followed by a turn toward the west and an increase in forward speed
during the remainder of the forecast period.  The track guidance is
in good agreement with this scenario through 96 hours.  After that,
there remains some spread on whether Orlene will turn more
northward, as favored by the GFS, or continue westward as favored by
the ECMWF. The new forecast track is again similar to the previous
track and lies near the center of the cluster of the consensus and
dynamical models.

Orlene is experiencing 15-20 kt of southwesterly vertical wind
shear, and this is likely to continue for about another 24 hours.
After that time, the dynamical models forecast the shear to decrease
while the cyclone moves near and parallel to the 26C sea surface
temperature isotherm.  These conditions, combined with abundant dry
air seen west of the cyclone in water vapor imagery, should lead to
gradual weakening through the forecast period.  The new intensity
forecast is an again an update of the previous forecast, and it lies
near the upper edge of the envelope of intensity guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 19.7N 118.7W   75 KT  85 MPH
 12H  14/0600Z 19.9N 118.8W   70 KT  80 MPH
 24H  14/1800Z 20.1N 119.3W   60 KT  70 MPH
 36H  15/0600Z 19.9N 120.9W   55 KT  65 MPH
 48H  15/1800Z 19.7N 122.8W   50 KT  60 MPH
 72H  16/1800Z 19.5N 127.5W   40 KT  45 MPH
 96H  17/1800Z 19.5N 132.5W   40 KT  45 MPH
120H  18/1800Z 20.0N 136.5W   35 KT  40 MPH

$$
Forecaster Beven

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