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TROPICAL STORM DOLORES DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052015
400 AM CDT SUN JUL 12 2015

Satellite data indicate that a CDO pattern is developing over the
low-level center of the tropical cyclone located south of Acapulco,
Mexico. A 0428 UTC ASCAT-B scatterometer pass indicated 40-43 kt
winds in the northern semicircle and the ship Seoul Express, call
sign DHBN, which has been traversing the northeastern quadrant,
reported 35-kt and 33-kt winds at 0300 UTC and 0600 UTC,
respectively. Based on these data, the system has been upgraded to
Tropical Storm Dolores.

The initial motion is 300/10 kt. There is no significant change to
the previous forecast track or reasoning. With the exception of the
GFDL model, which has a known right-bias near Mexico, the remainder
of the NHC model guidance is now tightly clustered about a general
west-northwestward motion for the next five days as a strong ridge
to the north of Dolores remains entrenched across the U.S. southern
Plains and northern Mexico. By day 3 and beyond, a gradual decrease
in forward speed is expected as the western portion of the ridge
weakens. The official forecast track is similar to the previous
advisory and lies close to the multi-model consensus TVCE.

Dolores is expected to remain in a very favorable environment for
significant strengthening to occur, especially with large
upper-level lows located to the northwest and to the east of the
cyclone helping to evacuate mass from the system. However, UW-CIMMS
shear analyses indicate that southwesterly mid-level shear has been
undercutting the otherwise favorable upper-level outflow pattern,
which has resulted in most of the deep convection remaining in the
northern semicircle of Dolores. This pattern is expected to continue
for the next 48 hours or so, followed by a more favorable outflow
regime and lower shear. As a result, at least steady intensification
is forecast throughout the 5-day period, with Dolores expected to
become a major hurricane by 120 h. The official intensity forecast
is a little above the previous advisory forecast, and is similar to
the intensity consensus model ICON through 96 hours and a little
above ICON at 120 hours.

Although the current track forecast keeps the center of Dolores and
the core of strongest winds offshore of southern Mexico, only a
small deviation to the north of the projected track and-or an
expansion of the 34-kt wind field would require the issuance of
tropical storm watches or warnings for a  portion of the
southwestern coast of Mexico. At the present time, however, the
wind flow is expected to be from an easterly direction along the
mountainous coastal areas of Mexico, which should act to keep the
current tropical-storm-force wind field just offshore.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 14.6N 101.1W   45 KT  50 MPH
 12H  12/1800Z 15.4N 102.4W   50 KT  60 MPH
 24H  13/0600Z 16.4N 104.3W   60 KT  70 MPH
 36H  13/1800Z 17.0N 105.8W   70 KT  80 MPH
 48H  14/0600Z 17.6N 107.1W   75 KT  85 MPH
 72H  15/0600Z 18.8N 109.1W   80 KT  90 MPH
 96H  16/0600Z 19.5N 110.6W   90 KT 105 MPH
120H  17/0600Z 20.0N 113.0W  100 KT 115 MPH

$$
Forecaster Stewart

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