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HURRICANE BLANCA DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP022015
1000 PM CDT WED JUN 03 2015

Blanca's convection has continued to decrease in intensity this
evening, and the eye observed in infrared satellite imagery has been
filling.  Dvorak T-numbers have dropped across the board, but the
intensity is being held at 120 kt based on a blend of current
intensity numbers.  Microwave imagery does not show the development
of concentric eyewalls, which often leads to disruptions in
intensification, but an 0030Z SSMIS pass did indicate that some dry
air may be wrapping into the circulation.  There's also the
possibility that upwelling of cooler water could be an issue, but
it's impossible to know that in real time.

The hurricane has been drifting southwestward during the past 6-12
hours.  Model guidance is in agreement that Blanca should begin
to accelerate toward the northwest on Thursday in response to a
amplifying mid-level trough along the U.S. west coast and building
high pressure over northern Mexico.  However, some of the track
models (most notably the GFS, HWRF, and GFDL) have again shifted
westward a bit.  As a result, the updated NHC track forecast is
slightly west of the previous forecast between 72-120 hours.

Despite the hurricane's recent convective changes, the microwave
data showed that the eyewall remains intact, and low vertical shear
and a generally moist environment should be conducive to support
further strengthening during the next 36 hours.  In addition, once
Blanca begins moving toward the northwest, it would escape any
potential areas of upwelled cooler water.  The GFS, ECMWF, SHIPS,
and LGEM all show Blanca peaking in intensity at 36 hours, and the
updated NHC intensity forecast follows suit by showing a maximum
intensity right near the category 4/5 boundary Friday morning.
After that, increasing shear, cooler water, and a drier, more stable
atmosphere should lead to rapid weakening, especially after 72
hours.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 12.0N 104.7W  120 KT 140 MPH
 12H  04/1200Z 12.6N 105.1W  125 KT 145 MPH
 24H  05/0000Z 13.7N 106.0W  130 KT 150 MPH
 36H  05/1200Z 15.0N 107.2W  135 KT 155 MPH
 48H  06/0000Z 16.4N 108.5W  130 KT 150 MPH
 72H  07/0000Z 19.1N 110.2W  100 KT 115 MPH
 96H  08/0000Z 21.9N 111.3W   60 KT  70 MPH
120H  09/0000Z 24.9N 112.7W   35 KT  40 MPH

$$
Forecaster Berg

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