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TROPICAL STORM BLANCA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP022015
1000 PM CDT MON JUN 01 2015

Blanca is gradually intensifying.  Satellite imagery shows the
cyclone maintaining a small CDO dominated by very cold-topped deep
convection, with a vigorous primary band over the southeastern
portion of the circulation.  Microwave satellite data, however,
indicate that Blanca's developing inner core currently lacks much
organization.  Regardless, anticyclonic flow over Blanca is also
expanding and becoming better established, indicative of a
continued decrease in shear.  A blend of Dvorak intensity estimates
is used to set the initial intensity to 45 kt.

Blanca has been meandering southward, but the overall motion is
essentially stationary.  The cyclone should remain trapped in a
col area during the next 36 hours, but there should be just enough
northerly or north-northwesterly flow to nudge the center of Blanca
on a general southerly course.  By 72 hours, the synoptic steering
over the eastern Pacific should change as an unusually deep longwave
trough settles into southern California and weak mid-level ridging
near Baja California shifts eastward and strengthens. This pattern
should cause Blanca to accelerate on a heading between northwest and
north-northwest beginning on Thursday.  Only small adjustments were
made to the NHC track forecast during the first 36-48 hours, but
the track has been shifted to the right of the previous one between
72-120 hours, which is close to the multi-model consensus (TVCE).

Northwesterly shear affecting the cyclone is forecast to decrease
considerably within 24 hours and remain low for a couple of days
after that, while thermodynamic parameters in the near-storm
environment should be exceptionally conducive for rapid
intensification.  An eastward-traveling upper-level shortwave trough
moving through Mexico in 48-72 hours could also enhance Blanca's
outflow, increasing the likelihood of a significant deepening during
this time.  Late in the forecast period, east-southeasterly shear
and cooler waters should result in weakening, especially by day 5.
The NHC intensity forecast is increased above the previous one and
is closest to the FSU Superensemble and SHIPS model output, and well
above the weaker regional model solutions.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 13.2N 104.0W   45 KT  50 MPH
 12H  02/1200Z 13.0N 104.2W   55 KT  65 MPH
 24H  03/0000Z 12.9N 104.4W   75 KT  85 MPH
 36H  03/1200Z 12.7N 104.5W   90 KT 105 MPH
 48H  04/0000Z 12.7N 104.3W  105 KT 120 MPH
 72H  05/0000Z 14.5N 105.3W  120 KT 140 MPH
 96H  06/0000Z 16.9N 107.7W  105 KT 120 MPH
120H  07/0000Z 20.1N 108.8W   85 KT 100 MPH

$$
Forecaster Kimberlain

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