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TROPICAL STORM BLAS DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032016
900 PM MDT SUN JUL 03 2016

The satellite presentation of Blas has not changed much since the
previous advisory, with the cyclone featuring large convective bands
and a developing CDO feature.  A GCOM/AMSR-2 image from 2042 UTC
showed a mid-level eye feature displaced about 30 n mi southwest of
the low-level center, consistent with about 10 kt of northeasterly
shear.  Satellite classifications remain T3.5/55 kt from TAFB and
SAB, and that is the initial intensity.  The intensity forecast
reasoning remains unchanged, as Blas should continue to strengthen
at a steady rate for the next 48 hours over warm SSTs and in a low
to moderate shear environment.  After 48 hours the SSTs cool
steadily along the forecast track, especially at days 4 and 5, and
quick weakening is forecast by then.  The NHC intensity forecast is
close to or a bit above the SHIPS model at the high end of the
guidance through 48 hours, and trends toward the weaker LGEM late in
the period.  Its worth noting that the HWRF and GFDL models are much
weaker with Blas compared to the statistical models for this cycle.

The initial motion estimate is 285/10.  The dominant steering
mechanism through the forecast period is a mid-level ridge centered
over northern Mexico and extending westward across the eastern
Pacific.  This feature should steer Blas on a general westward to
west-northwestward track through the forecast period.  The track
model guidance is in very good agreement with small spread through
day 4, but the spread increases a bit at day 5.  By then the GFS
shows more of a poleward turn as the ridge is eroded by a closed
mid/upper-level low northeast of the Hawaiian Islands, while the
ECMWF and UKMET show less influence from the upper low.  The new NHC
forecast is close to a blend of the GFS and ECMWF solutions and is
in the middle of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 12.4N 112.2W   55 KT  65 MPH
 12H  04/1200Z 12.9N 113.9W   65 KT  75 MPH
 24H  05/0000Z 13.5N 116.4W   80 KT  90 MPH
 36H  05/1200Z 14.0N 118.8W   90 KT 105 MPH
 48H  06/0000Z 14.5N 121.2W  100 KT 115 MPH
 72H  07/0000Z 15.9N 125.7W  105 KT 120 MPH
 96H  08/0000Z 17.3N 129.5W   85 KT 100 MPH
120H  09/0000Z 19.1N 132.9W   60 KT  70 MPH

$$
Forecaster Brennan

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