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TROPICAL STORM ORLENE DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP162016
800 PM PDT THU SEP 15 2016

Several microwave images have arrived since the previous advisory,
revealing that the low-level center of Orlene is displaced to the
east of a small area of persistent deep convection.  Dvorak data-T
numbers from TAFB, SAB, and the UW-CIMSS ADT vary greatly, mainly
due to the sensitivity of the Dvorak technique to the location of
the low-level center.  The initial intensity has been conservatively
lowered by 10 knots to 55 kt based on a blend of the Dvorak
estimates and an 1823 UTC ASCAT pass.  The ASCAT pass only showed a
maximum of about 45 kt, so this may still be a little high.

Orlene continues to move into a very dry and thermodynamically
stable environment, highlighted by a field of stratocumulus clouds
that wrap around the western half of the tropical storm.  All of
the intensity guidance continues to indicate that this hostile
environment will cause steady weakening.  The intensity forecast has
been lowered from the previous advisory, but is a little higher than
the latest intensity consensus out of respect to the GFS which
shows more gradual weakening.  The GFS and HWRF suggest that the
cyclone will lose all deep convection and become post-tropical
within 96 hours, which is reflected in the official forecast.

Almost no change has been made to the track forecast, aside from a
slight eastward adjustment of the initial position.  The global
models remain in good agreement that the mid-level ridge
located to the north of Orlene will steer the tropical storm
westward over the next three days.  After 72 hours, low-level
easterlies should continue to steer the remnant low generally
westward at a slightly slower forward speed. The track forecast
remains very close to the multi-model ensemble mean.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 19.7N 123.8W   55 KT  65 MPH
 12H  16/1200Z 19.5N 125.4W   50 KT  60 MPH
 24H  17/0000Z 19.4N 127.7W   45 KT  50 MPH
 36H  17/1200Z 19.3N 130.2W   40 KT  45 MPH
 48H  18/0000Z 19.3N 132.8W   35 KT  40 MPH
 72H  19/0000Z 19.3N 137.9W   30 KT  35 MPH
 96H  20/0000Z 20.0N 142.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  21/0000Z 20.5N 145.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart/Zelinsky

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