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TROPICAL STORM BLAS DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032016
300 AM MDT MON JUL 04 2016

During the past few hours, the satellite appearance of Blas has
changed from consisting of primarily a long curved band to a large
central dense overcast (CDO) feature. Recent AMSU data showed that a
nearly closed mid-level eye feature with a diameter of about 35 nmi
has also developed within the southwestern portion of the CDO. A
0420 UTC ASCAT pass revealed surface winds near 50 kt in the
northeastern quadrant and a radius of maximum winds of about 30 nmi.
UW-CIMSS ADT estimates were near 55 kt. These data support an
intensity of 55 kt at 0600 UTC. However, since that time the
satellite signature has improved, so the advisory intensity has
been increased to 60 kt.

The initial motion estimate remains a steady 285/10 kt. There is no
significant change to the previous forecast reasoning and the
latest NHC model guidance suite remains tightly packed. Therefore,
the new forecast track is essentially just an update of the
previous advisory track due to the subtropical ridge to the north of
Blas remaining strong throughout the entire forecast period. The
new NHC forecast closely follows the consensus model TVCE and
basically lies down the middle of the guidance envelope.

The atmospheric and oceanic environment is expected to be quite
favorable for Blas to strengthen during the next 48-60 hours. Since
the global models are forecasting Blas' outflow pattern to gradually
expand and become more symmetrical, along with the development of
both poleward and equator outflow channels, a period of rapid
intensification is expected for at least the next 24 hours. Blas is
expected to achieve its peak intensity around 48 hours or so when
the vertical wind shear is forecast to be low at around 5 kt. After
that, gradual weakening should begin by 72 hours when Blas will be
moving over sub-26C SSTs, creating cold upwelling/mixing beneath the
cyclone. The NHC intensity forecast is well above the consensus
model IVCN, and closely follows the LGEM statistical-dynamical
intensity model.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 12.7N 113.2W   60 KT  70 MPH
 12H  04/1800Z 13.2N 114.8W   70 KT  80 MPH
 24H  05/0600Z 13.8N 117.4W   85 KT 100 MPH
 36H  05/1800Z 14.2N 119.8W   95 KT 110 MPH
 48H  06/0600Z 14.8N 122.1W  105 KT 120 MPH
 72H  07/0600Z 16.1N 126.5W  100 KT 115 MPH
 96H  08/0600Z 17.5N 130.3W   80 KT  90 MPH
120H  09/0600Z 19.4N 133.6W   55 KT  65 MPH

$$
Forecaster Stewart

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