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TROPICAL STORM BLAS DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032016
300 PM MDT SUN JUL 03 2016

Blas' cloud pattern has not changed appreciably in organization
since the previous advisory.  Visible and microwave satellite
imagery suggests that the cyclone's low-level center is located at
the northern tip of a long band whose convective tops have been
slowly warming.  This structure suggests that Blas' rate of
intensification is not as fast as was suspected earlier, possibly
due to some northeasterly shear and likely the cyclone's large size.
The initial intensity is set to 55 kt based on the latest Dvorak
intensity estimates of T3.5 from TAFB and SAB.

The initial motion estimate is a steady 285/11.  There has been no
change to the track forecast philosophy since the previous
advisory.  Blas is forecast to move west-northwestward throughout
the forecast period along the southern periphery of a deep-layer
subtropical ridge extending westward from northern Mexico. The
GFS and ECMWF solutions have come into much better agreement beyond
day 3, and the overall spread in the guidance is low through day 5.
The new NHC forecast track is shifted to the north some, and lies
very near the multi-model consensus.

There does not appear to be anything conspicuous on the large scale
that would prevent Blas from intensifying into a major hurricane
during the next few days, and a large one at that.  The NHC
intensity forecast through day 3 is near or just below the
statistical guidance, which is unanimously calling for Blas to
become an intense hurricane.  By 96 hours, even though the shear is
forecast to remain low, the cyclone should be moving over steadily
cooler waters and entering a drier and more stable environment. This
should promote a weakening trend that will likely become more rapid
by the end of the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 12.2N 111.4W   55 KT  65 MPH
 12H  04/0600Z 12.8N 113.0W   65 KT  75 MPH
 24H  04/1800Z 13.4N 115.4W   75 KT  85 MPH
 36H  05/0600Z 13.9N 117.7W   90 KT 105 MPH
 48H  05/1800Z 14.3N 120.0W  100 KT 115 MPH
 72H  06/1800Z 15.5N 124.3W  110 KT 125 MPH
 96H  07/1800Z 16.8N 128.6W   90 KT 105 MPH
120H  08/1800Z 18.4N 132.3W   70 KT  80 MPH

$$
Forecaster Kimberlain

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