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TROPICAL STORM IGNACIO DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122015
200 PM PDT WED AUG 26 2015

Ignacio continues to strengthen with plenty of tightly curved bands
around the center and an impressive outflow pattern.  Dvorak
estimates from TAFB/SAB are both 55 kt, and this will be the initial
intensity.  The environment appears favorable for further
intensification with light-to-moderate shear and warm waters for the
next several days anticipated.  There remains some question as to
the amount of vertical shear expected, so it is prudent not to show
rapid intensification at this time.  Still, the most likely scenario
is continued strengthening, which is in line with the latest
intensity guidance.  The NHC forecast is raised from the previous
one and lies above the intensity consensus, just a bit below the
Florida State Superensemble.  Most of the guidance is showing some
weakening at long range due to an increase in shear and less
favorable thermodynamic conditions.

Scatterometer data indicate the center of Ignacio has continued
moving west-southwestward a little longer than anticipated, although
recent satellite images suggest a more westward track has started.
The current motion estimate is 270/10.  A west- northwestward track
is likely to start overnight and continue for the next several days
while Ignacio is steered around the subtropical ridge.  There is
considerable uncertainty about the long-range forecast, with the
models struggling on how intact the ridge remains to the northeast
of Hawaii.  On this cycle, the ECMWF and HWRF models have shifted
well leftward, dragging the consensus a good bit south of the
previous forecast.  The official forecast is moved in that
direction, although remaining north of the model consensus at day 5.

FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 11.9N 136.2W   55 KT  65 MPH
 12H  27/0600Z 12.3N 137.6W   65 KT  75 MPH
 24H  27/1800Z 13.2N 139.5W   75 KT  85 MPH
 36H  28/0600Z 14.1N 141.4W   85 KT 100 MPH
 48H  28/1800Z 15.0N 143.2W   95 KT 110 MPH
 72H  29/1800Z 16.5N 146.2W   90 KT 105 MPH
 96H  30/1800Z 17.8N 149.4W   85 KT 100 MPH
120H  31/1800Z 19.0N 152.5W   75 KT  85 MPH

$$
Forecaster Blake

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