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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042014
500 AM AST SUN AUG 24 2014

The satellite presentation of the tropical depression has gradually
improved overnight.  Convection has increased to the northeast
of the center and a little more banding is noted.   Although the
pressure has dropped a few millibars during the past 6 to 12 hours,
data from an Air Force Reserve Hurricane Hunter aircraft
indicate that the cyclone remains a 30-kt tropical depression.

Fixes from the aircraft yield an initial motion of 325/8 kt. The
cyclone is expected to slow down and turn north-northwestward today
into a break in the ridge caused by a mid- to upper-level trough
that is currently moving off the U.S. east coast.  This trough is
forecast to dig southeastward during the next 24 to 36 hours before
lifting northeastward on Tuesday.  The track guidance has shifted
significantly eastward this cycle, with the exception of the latest
ECMWF, which is very similar to its 1200 UTC run.  The eastward
shift in most of the models appears to be the result of increased
interaction of the cyclone with the aforementioned trough during the
next 48 hours.  This leads to a more north-northwestward or
northward motion during the next day or so.  Once the trough lifts
out, most of the guidance shows a bend back toward the northwest,
before the cyclone turns northward and northeast around a
subtropical ridge to its east.  The NHC track has been shifted
eastward, but it remains along the western side of the
guidance envelope out of respect for the ECMWF and continuity of the
previous forecasts. The new track forecast is closest to the HWRF,
but is well west of the latest multi-model consensus.  Future
eastward adjustments may be required if the eastward model trend
continues.  Given that a large spread remains in the guidance,
the confidence in the track forecast remains lower than normal.

Light to moderate northwesterly shear is expected during the next
few days.  However, the shear is not expected to be strong enough to
prevent strengthening, and the official forecast calls for gradual
intensification throughout the forecast period. The NHC intensity
forecast is close to the SHIPS guidance and the intensity
consensus ICON.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 22.9N  73.3W   30 KT  35 MPH
 12H  24/1800Z 23.7N  73.7W   40 KT  45 MPH
 24H  25/0600Z 24.4N  73.9W   45 KT  50 MPH
 36H  25/1800Z 25.0N  74.0W   50 KT  60 MPH
 48H  26/0600Z 25.9N  74.1W   55 KT  65 MPH
 72H  27/0600Z 28.5N  75.5W   60 KT  70 MPH
 96H  28/0600Z 31.5N  75.0W   65 KT  75 MPH
120H  29/0600Z 34.0N  70.0W   70 KT  80 MPH

$$
Forecaster Brown

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