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TROPICAL STORM ERIKA DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052015
500 PM AST TUE AUG 25 2015

After becoming quite disorganized in appearance earlier today,
Erika has made a bit of a comeback with increased deep convection
near and to the south of the center.  Data from the Air Force
Hurricane Hunters indicate that the intensity is near 35 kt and
this is consistent with Dvorak estimates from both TAFB and SAB.
Erika has limited upper-level outflow over the northern semicircle
of the circulation, and microwave data suggest that the cyclone has
been ingesting some dry mid-level air.  As in the previous
forecast, there is considerable uncertainty as to the future
intensity of this tropical cyclone.  The SHIPS guidance indicates
increasing west-northwesterly shear over the next few days, and the
GFS and ECMWF global models do not strengthen the system during the
forecast period.  The HWRF and GFDL models do show strengthening,
however, but along a track to the right of most of the guidance.
The official intensity forecast has been reduced a bit from the
previous one and is close to the model consensus.

A center fix from the aircraft indicates that the motion continues
to be near 280/17.  A mid-level subtropical ridge to the north of
Erika should steer the system on a west-northwestward track for the
next several days.  Late in the forecast period, there is
significant spread in the models, with those models that depict a
weaker system being farther south and west and those having a
stronger cyclone farther to the north and east.  The official track
forecast has been adjusted a little to the left of the previous one
and is in line with the latest dynamical model consensus.

Some of the tropical storm watches for the islands of the
northeastern Caribbean may need to be changed to warnings on the
next advisory package.

FORECAST POSITIONS AND MAX WINDS

INIT  25/2100Z 15.6N  52.8W   35 KT  40 MPH
 12H  26/0600Z 16.1N  55.1W   35 KT  40 MPH
 24H  26/1800Z 16.7N  58.4W   40 KT  45 MPH
 36H  27/0600Z 17.4N  61.4W   45 KT  50 MPH
 48H  27/1800Z 18.2N  64.3W   50 KT  60 MPH
 72H  28/1800Z 20.3N  69.7W   50 KT  60 MPH
 96H  29/1800Z 22.5N  74.0W   55 KT  65 MPH
120H  30/1800Z 25.0N  78.0W   65 KT  75 MPH

$$
Forecaster Pasch

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