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Tropical Depression ELEVEN


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TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
1100 PM AST SUN SEP 27 2015

Late-afternoon visible satellite imagery indicates that the
circulation of the low pressure area located midway between the
Bahamas and Bermuda has become well defined.  Since the low has
already had persistent and organized deep convection, the system is
being declared a tropical depression.  A 2312 UTC SSMI/S overpass
indicated that the center of the depression has become at least
partially exposed to the northwest of a large convective mass due to
moderate northwesterly shear.  The initial wind speed is set to 30
kt, based on a T2.0/30 kt classification from TAFB.  The depression
is expected to be blasted by strong north-northwesterly or northerly
winds associated with the tail of an upper-level trough over the
central Atlantic beginning on Monday.  In fact, global models show
the shear being sufficiently strong enough to result in the cyclone
either becoming a remnant low or dissipating within a few days.  The
intensity forecast is below the multi-model consensus through the
forecast period, closest to the HWRF solution.

A low- to mid- level ridge north and northeast of the cyclone is
steering the lower half of the depression's circulation
northwestward while increasing northwesterly winds aloft are
opposing this motion.  The net deep-layer mean flow is therefore
providing for only a slow northwestward motion of 315/02 kt, a
rather uncertain estimate considering the scatter of recent fixes.
This synoptic pattern is expected to persist for the next couple of
days, resulting in a the cyclone's drifting west-northwestward or
northwestward.  The low- to mid-level ridge is forecast to shift
eastward in 2-3 days as a trough reaches the eastern seaboard of the
United States, and the increasingly shallow system should turn
northwestward and north-northwestward at a faster forward speed if
it still exists.  The track forecast is close to a blend of the GFS
and ECMWF model solutions.

FORECAST POSITIONS AND MAX WINDS

INIT  28/0300Z 27.5N  68.7W   30 KT  35 MPH
 12H  28/1200Z 27.7N  69.4W   30 KT  35 MPH
 24H  29/0000Z 27.9N  69.9W   30 KT  35 MPH
 36H  29/1200Z 28.2N  70.4W   30 KT  35 MPH
 48H  30/0000Z 28.8N  70.8W   30 KT  35 MPH
 72H  01/0000Z 31.0N  71.6W   30 KT  35 MPH
 96H  02/0000Z...DISSIPATED

$$
Forecaster Kimberlain

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