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Tropical Storm ROSLYN Forecast Discussion


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000
WTPZ43 KNHC 280835
TCDEP3

TROPICAL STORM ROSLYN DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182016
200 AM PDT WED SEP 28 2016

The last bit of deep convection dissipated just after the release of
the previous advisory, and all that is left is some shower activity
displaced well to the northeast of Roslyn's center due to 30-35 kt
of southwesterly shear.  Recent ASCAT data indicate that the system
is still producing a small area of tropical-storm-force winds in
the southeastern quadrant, and the initial intensity remains 35 kt.
Continued strong shear and cooler waters should cause the cyclone
to gradually spin down during the next couple of days.  Since it is
unlikely that Roslyn will be able to reproduce organized deep
convection, the cyclone is expected to degenerate to a remnant low
later today.  The global models all suggest that the remnant low
will dissipate by day 3, if not sooner.

The initial motion is north-northeastward, or 025/8 kt.  Roslyn is
expected to turn northward later today as it moves around a
deep-layer trough extending southwestward from southern California.
The shallow, convection-less remnant low should then turn
northwestward and west-northwestward by 48 hours, steered by the
low-level subtropical ridge.  The new official track closely follows
the TVCN multi-model consensus, which required an eastward shift
from the previous track, primarily during the first 24 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  28/0900Z 20.2N 115.5W   35 KT  40 MPH
 12H  28/1800Z 21.2N 115.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  29/0600Z 22.2N 116.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  29/1800Z 23.0N 117.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  30/0600Z 23.2N 117.8W   15 KT  15 MPH...POST-TROP/REMNT LOW
 72H  01/0600Z...DISSIPATED

$$
Forecaster Berg