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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP042016
300 AM MDT THU JUL 07 2016

Tropical Depression Four-E has changed little overnight. A 0458Z
ASCAT-B overpass indicated a broad, weak inner-core wind field with
the low-level center located at or south of 12N latitude. However,
passive microwave satellite data indicate a fairly well-developed
mid-level circulation displaced more than 30 nmi north-northwest of
the low-level center due to southeasterly vertical wind shear. The
ASCAT data also indicated a couple of 35-kt surface wind vectors.
However, convection near the center has noticeably weakened and
become less organized since that pass, so the cyclone is being
maintained as a 30-kt depression, which is supported by a blend of
satellite intensity estimates from TAFB, SAB, and UW-CIMSS.

The initial motion estimate is still 285/07 kt, based primarily on a
blend of microwave and scatterometer fix positions of the low-level
and mid-level circulation centers. Despite the difficulty in
locating the exact center of the depression, the NHC model guidance
is in remarkably good agreement on the future track of the cyclone.
The strong subtropical ridge to the north of the depression is
forecast to remain nearly stationary throughout the forecast period,
and even amplify somewhat in 24-72 hours, driving the cyclone in a
general westward motion. After that time, the cyclone is expected to
turn toward the west-northwest as the system moves around the
southwestern periphery of the ridge. The NHC official forecast track
essentially lies down the middle of the guidance envelope, and
closely follows the multi-model consensus TVCE.

The depression is experiencing mid-level dry air entrainment and
modest mid-level shear conditions, which have combined to disrupt
the inner-core wind field somewhat. However, the overall environment
is quite favorable for strengthening to occur, so once the
inner-core region recovers later today, steady strengthening is
expected through 36 h. However, around 48 h or so, the cyclone is
expected to pass near or just south of a pronounced cold wake left
behind by Hurricane Blas when it traversed this same area a couple
of days ago. This could produce a slightly more stable environment,
so the intensification trend at that time is leveled off some. From
72 hours and beyond, however, conditions become quite favorable
for at least steady strengthening, and some of the models are even
calling for the cyclone to become a major hurricane by 120 h. The
official intensity forecast is similar to the previous advisory, and
closely follows a blend of the SHIPS and LGEM models through 72
hours, but is a little lower than those models on days 4 and 5.

FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 12.6N 110.2W   30 KT  35 MPH
 12H  07/1800Z 12.7N 111.2W   35 KT  40 MPH
 24H  08/0600Z 12.8N 112.6W   45 KT  50 MPH
 36H  08/1800Z 12.9N 114.2W   55 KT  65 MPH
 48H  09/0600Z 13.1N 115.9W   60 KT  70 MPH
 72H  10/0600Z 13.1N 119.4W   75 KT  85 MPH
 96H  11/0600Z 14.0N 123.6W   85 KT 100 MPH
120H  12/0600Z 15.6N 127.4W   95 KT 110 MPH

$$
Forecaster Stewart

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