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TROPICAL STORM ERIKA DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052015
1100 AM AST THU AUG 27 2015

Erika is not well organized at this time.  Although deep convection
increased overnight and early today during the diurnal maximum,
with considerable lightning activity, banding features were
lacking.  The convection is also not well organized on the
Guadeloupe radar imagery.  Recent high-resolution visible imagery
shows the low-level center becoming exposed, again, to the
northwest of the main area of thunderstorms.  Data from the aircraft
do not indicate any strengthening, and the initial intensity is kept
at 45 kt.

The latest aircraft fixes show that the center has apparently
reformed farther to the south of previous estimates.  With some
adjustments to the previous location, the initial motion estimate is
kept at 270/14.  For the next few days, Erika should move
west-northwestward to the south of a mid-level subtropical ridge.
Later in the forecast period, as the tropical cyclone nears the
western periphery of the ridge, a turn to the northwest and
north-northwest should occur.  However there is uncertainty as to
how soon and how sharp this turn will take place.  The future track
of Erika is also dependent on its intensity, with a weaker system
likely to move more to the west and a stronger cyclone more to the
east.  There is substantial spread in the track models at days 3 to
5, partially due to differences in model-predicted intensity.  The
official track forecast has been shifted to the left of the previous
one mainly due to the adjustment in the current center position.
This is close to the model consensus.

As expected, Erika is being disrupted by an unfavorable atmospheric
environment, and this disruption is expected to continue for the
next couple of days.  No significant strengthening is expected until
later in the forecast period.  In addition, with the reformation of
the center to the south of the previous track, the likelihood of
interaction with the land mass of Hispaniola has increased.  This
has implications for Hispaniola, of course, but also for the track
and intensity of Erika after that. In short, potential impacts for
the Bahamas and beyond are unusually uncertain.


FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 16.4N  63.3W   45 KT  50 MPH
 12H  28/0000Z 17.5N  65.1W   45 KT  50 MPH
 24H  28/1200Z 18.8N  67.8W   45 KT  50 MPH
 36H  29/0000Z 20.0N  70.5W   50 KT  60 MPH
 48H  29/1200Z 21.4N  73.1W   50 KT  60 MPH
 72H  30/1200Z 23.9N  77.1W   55 KT  65 MPH
 96H  31/1200Z 26.5N  79.5W   65 KT  75 MPH
120H  01/1200Z 28.5N  80.0W   75 KT  85 MPH

$$
Forecaster Pasch

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