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Tropical Storm Lee Discussion Number   9
NWS National Hurricane Center Miami FL       AL142017
1100 PM AST Sat Sep 16 2017

Lee has a classic shear pattern appearance in satellite imagery this
evening, with the center on the northern edge of a large convective
burst due to the effects of 15-20 kt of northwesterly vertical
shear.  Two recent ASCAT overpasses indicate that the maximum winds
are about 35 kt in the southern semicircle, with no winds of
tropical-storm-force in the northern semicircle.  The initial
intensity of 35 kt is based on the scatterometer data.

The initial motion is 275/7. Lee is moving along the south side of a
weak mid-level ridge.  After about 24 h, the ridge is expected to
weaken and allow Lee to turn west-northwestward, a motion that
should continue through the forecast period.  The new track forecast
is similar to the previous forecast and lies mainly between the
ECMWF and the HFIP corrected consensus models.

Lee is expected to encounter strong upper-level winds through the
forecast period, with vertical shear values likely to exceed 30 kt
after 48 h.  While some short-term spin up due to convective bursts
cannot be ruled out, overall the environment is not favorable for
significant strengthening.  Indeed, the intensity guidance calls
for gradual weakening, and the GFS and ECMWF models forecast the
cyclone to completely dissipate by 120 h.  The new intensity
forecast is weaker than the previous forecast and now calls for Lee
to degenerate to a remnant low by 96 h.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 12.8N  34.9W   35 KT  40 MPH
 12H  17/1200Z 12.9N  36.0W   35 KT  40 MPH
 24H  18/0000Z 13.1N  37.5W   35 KT  40 MPH
 36H  18/1200Z 13.7N  39.2W   35 KT  40 MPH
 48H  19/0000Z 14.4N  41.0W   30 KT  35 MPH
 72H  20/0000Z 16.0N  44.5W   30 KT  35 MPH
 96H  21/0000Z 17.5N  48.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  22/0000Z 19.0N  52.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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