000
WTPZ42 KNHC 261433
TCDEP2

TROPICAL STORM IGNACIO DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122015
800 AM PDT WED AUG 26 2015

Convection has been increasing near the center of Ignacio with a
central dense overcast feature taking shape.  The latest microwave
images also show more organization, with signs of a primitive inner
core. A blend of the subjective Dvorak estimates gives an initial
wind speed of 50 kt for this advisory.

Conditions appear favorable for strengthening of Ignacio, with a
warm and moist environment likely for the next several days in the
storm's path.  The biggest question mark is the vertical wind shear,
which some models show increasing a bit in a day or two.  Perhaps
this is why none of the reliable models show any more than gradual
strengthening, although the SHIPS rapid intensification index shows
a 28 percent chance of a 30-kt change over the next 24 hours.
Considering most of the guidance has had a low bias this year, the
official forecast will stay higher than the model consensus, but not
quite as high as the Florida State Superensemble. Some weakening is
anticipated by the end of the forecast due to increasing shear and
cooler waters.

A recent microwave pass shows that Ignacio is on track and is
moving about 265/8.  The storm should be moving around the
southern and southwestern periphery of the subtropical ridge for
the next several days, causing the storm to move westward today and
then west-northwestward on Thursday through late week.  The latest
guidance has shifted a bit to the north at day 3 and beyond,
perhaps due to a slightly weaker subtropical ridge to the northeast
of Hawaii.  The official forecast is adjusted northward at long
range, although it remains south of the model consensus at 120
hours.


FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 12.2N 135.1W   50 KT  60 MPH
 12H  27/0000Z 12.3N 136.4W   60 KT  70 MPH
 24H  27/1200Z 13.1N 138.2W   70 KT  80 MPH
 36H  28/0000Z 14.1N 140.2W   75 KT  85 MPH
 48H  28/1200Z 15.1N 142.0W   85 KT 100 MPH
 72H  29/1200Z 16.5N 145.1W   90 KT 105 MPH
 96H  30/1200Z 18.0N 148.5W   85 KT 100 MPH
120H  31/1200Z 19.3N 151.6W   75 KT  85 MPH

$$
Forecaster Blake