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TROPICAL STORM DANNY DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042015
500 AM AST WED AUG 19 2015

The cloud pattern has not changed significantly during the past few
hours. The convection near the center has been intermittent,
while a band of thunderstorm has been developing on the eastern
semicircle. The outflow to the west appears to be fair. Microwave
data do not show any significant increase in organization of the
inner core at this time. The initial intensity has been kept at 45
kt since the subjective Dvorak T-numbers have not changed.

SHIPS model indicate that Danny will continue to be embedded within
an environment of very light shear, and only dry air appears to be
the unfavorable factor for strengthening. In fact, the SHIPS rapid
intensification index RI continues to be high, but not as much as
it was indicated in the previous run. Most of the models call for
intensification during the next 3 to 4 days, but none is as
aggressive as the LGEM model, which makes Danny and intense
hurricane by the end of the forecast period. The official forecast
is closer to the consensus, and calls for a more modest
strengthening with some slight decrease in intensity as Danny
approaches the Lesser Antilles.

The center is difficult to locate on infrared images, and there are
some indications that Danny could be moving a little faster. Given
the uncertainties of the location of storm, and assuming that the
center is still under the convective canopy, the best estimate of
the initial motion is toward the west, but still at 12 kt. The
persistent subtropical ridge over the Atlantic will likely continue
to steer Danny on a general west to west-northwest track during the
next five days. The guidance envelope shifted northward in the last
run, but the ECMWF still favors a more westward track.  The NHC
forecast was shifted a little bit to the north, following the
multi-model consensus, and lies between the GFS and the ECMWF.


FORECAST POSITIONS AND MAX WINDS

INIT  19/0900Z 11.3N  40.2W   45 KT  50 MPH
 12H  19/1800Z 11.7N  41.6W   55 KT  65 MPH
 24H  20/0600Z 12.2N  43.2W   60 KT  70 MPH
 36H  20/1800Z 12.6N  44.6W   70 KT  80 MPH
 48H  21/0600Z 13.2N  46.3W   75 KT  85 MPH
 72H  22/0600Z 14.5N  50.0W   85 KT 100 MPH
 96H  23/0600Z 15.5N  54.0W   90 KT 105 MPH
120H  24/0600Z 16.5N  59.0W   80 KT  90 MPH

$$
Forecaster Avila

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