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TROPICAL STORM BLANCA DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP022015
1000 AM CDT MON JUN 01 2015

The convective pattern of the cyclone features a developing central
dense overcast and an expansive convective band to the east and
southeast of the center.  Based on the latest Dvorak classification
of T2.5/35 kt from TAFB, the cyclone is upgraded to Tropical Storm
Blanca on this advisory.  The SHIPS model and satellite analysis
from UW-CIMSS show about 20 kt of shear currently affecting Blanca.
However, the models show the shear quickly relaxing during the next
12 to 24 hours, which should allow Blanca to take advantage of an
otherwise favorable environment.  As a result, steady if not rapid
intensification is expected to begin soon.  In fact, the SHIPS RI
index shows a 74 percent chance of a 30-kt increase in the next 24
hours.  The official forecast follows this trend and shows a quicker
rate of intensification than the previous one through 48 hours.
Additional strengthening is expected later in the forecast period.
The new NHC forecast is close to the more aggressive SHIPS model and
is well above the IVCN intensity consensus.

Microwave imagery from AMSR2 on GCOM-W1 at 0743Z and from the GPM
satellite at 1031Z were helpful in establishing the initial
position, which is just a little to the right of the previous
advisory.  The track forecast philosophy remains unchanged.  A slow
northwestward or west-northwestward motion is expected today,
followed by a slow erratic motion through 72 hours as the steering
flow weakens.  Late in the period, a ridge will amplify over
northern Mexico which should result in a steadier motion toward the
northwest at days 4 and 5.  The new NHC track is a little to the
right of the previous one after an adjustment toward the latest TVCE
multi-model consensus.

Blanca is expected to remain well offshore of the southwestern coast
of Mexico through the forecast period.  However, some rainbands on
the outer periphery of the circulation could affect portions of the
coast during the next couple of days.

FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 13.5N 104.1W   35 KT  40 MPH
 12H  02/0000Z 13.8N 104.6W   45 KT  50 MPH
 24H  02/1200Z 13.8N 104.9W   65 KT  75 MPH
 36H  03/0000Z 13.6N 105.1W   75 KT  85 MPH
 48H  03/1200Z 13.4N 105.3W   85 KT 100 MPH
 72H  04/1200Z 13.4N 105.3W  100 KT 115 MPH
 96H  05/1200Z 15.5N 107.3W  110 KT 125 MPH
120H  06/1200Z 18.5N 110.0W  100 KT 115 MPH

$$
Forecaster Brennan

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