000
WTNT45 KNHC 290248
TCDAT5

TROPICAL STORM ERIKA DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052015
1100 PM EDT FRI AUG 28 2015

Dropsondes from the NOAA P3 flying around Hispaniola were very
helpful in locating the mean center of the broad circulation
associated with Erika, which is moving over the high terrain of
Hispaniola. There is plenty of deep convection associated with the
cyclone, and gusts to tropical storm force are being reported
in Barahona, on the south coast of the Dominican Republic. Given
that the circulation is interacting with land, the initial intensity
has been set at 40 kt. Erika is fighting both land and a hostile
wind shear environment, and it will be very difficult for the
cyclone to recover. Consequently, weakening in the short term is
indicated in the NHC forecast, and there is a strong likelihood
that Erika will degenerate to a tropical wave during its interaction
with land. However, if it survives, there is a very small
opportunity for Erika to regain tropical storm strength in the
Florida Straits and the southeastern Gulf of Mexico, where the
environment is less hostile. It is interesting to note, and to
remember, the fact that most of the state-of-the art dynamical
models were forecasting Erika to become a strong hurricane up to
yesterday, and today basically dissipate the cyclone.

The initial motion is uncertain, and the best estimate is toward the
west-northwest or 285 degrees at 17 kt. It seems that Erika has
changed very little in forward speed since its formation. However,
the cyclone is reaching the southwestern edge of the subtropical
ridge and the steering currents are weaker. Therefore, Erika is
forecast to slow down and turn to the northwest in about two days.
Once in the eastern Gulf of Mexico, a more northerly track is
anticipated. There is not much track guidance available tonight
since most of the models lose the circulation of Erika, and the NHC
forecast is following the weak perturbation observed in the model
fields.

The greatest short-term threat posed by Erika continues to be very
heavy rainfall over portions of Hispaniola and eastern Cuba. These
rains could produce flash floods and mudslides.

We must emphasize that although this would normally be an
appropriate time for a tropical storm watch for portions of southern
Florida, following typical timelines, we have elected to wait until
we see if Erika survives after it passes Hispaniola.  There is a
significant chance that no watches or warnings for Florida will be
required.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0300Z 18.5N  72.9W   40 KT  45 MPH...INLAND
 12H  29/1200Z 20.0N  75.0W   35 KT  40 MPH...INLAND
 24H  30/0000Z 22.0N  78.0W   30 KT  35 MPH...INLAND
 36H  30/1200Z 23.5N  80.5W   30 KT  35 MPH...OVER WATER
 48H  31/0000Z 25.0N  82.0W   35 KT  40 MPH
 72H  01/0000Z 26.5N  83.0W   35 KT  40 MPH
 96H  02/0000Z 28.5N  84.0W   40 KT  45 MPH
120H  03/0000Z 31.0N  84.0W   25 KT  30 MPH...INLAND

$$
Forecaster Avila