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Tropical Storm ROSLYN Forecast Discussion


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000
WTPZ43 KNHC 270234
TCDEP3

TROPICAL STORM ROSLYN DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182016
800 PM PDT MON SEP 26 2016

Southwesterly shear of about 20 kt is currently affecting Roslyn,
and this has caused the associated convection to be confined to the
north and northeast portions of the large circulation.  The initial
wind speed is held at 45 kt, based on the earlier ASCAT data, but
the satellite presentation suggests that this could be a little
generous.  Weakening is expected to begin soon due to a further
increase in shear and continued dry air entrainment.  Roslyn will
likely become a remnant low in 36 to 48 hours when it moves over
sea surface temperatures lower than 26 deg C.  The NHC intensity
forecast is identical to the previous one, and generally follows
the global model guidance.

Visible satellite images and microwave data suggest that Roslyn is
moving east-northeastward at 4 kt.  During the next day or so, the
tropical storm is expected to move northeastward in the flow between
a large mid- to upper-level cut off low near the northern Baja
California peninsula and a ridge over central Mexico.  After that
time, a turn to the north and northwest is expected when the
shallow cyclone becomes influenced by the low-level flow.  The NHC
track forecast is adjusted a little to the east of the previous
one, trending toward the latest consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 17.2N 118.4W   45 KT  50 MPH
 12H  27/1200Z 17.9N 117.7W   40 KT  45 MPH
 24H  28/0000Z 19.1N 117.0W   35 KT  40 MPH
 36H  28/1200Z 20.5N 116.9W   30 KT  35 MPH
 48H  29/0000Z 21.7N 117.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  30/0000Z 23.5N 118.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  01/0000Z...DISSIPATED

$$
Forecaster Cangialosi