Hurricane JULIO

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HURRICANE JULIO DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102014
800 AM PDT THU AUG 07 2014

Despite moving over decreasing sea surface temperatures, Julio is
continuing to strengthen.  The eye has become better defined during
the past few hours, and the cloud top temperatures in the eyewall
have cooled.  Subjective satellite intensity estimates are 90 kt
from TAFB and 77 kt from SAB, and objective estimates from the
UW-CIMSS ADT are near 100 kt.  The initial intensity is increased
to 90 kt based on a blend of these data.  The cirrus outflow is good
to excellent over the western semicircle and poor elsewhere.

Julio has turned a little to the left and the initial motion is now
280/16.  Julio is expected to remain south of the subtropical ridge
for the next few days, which will keep it on a westward to
west-northwestward trajectory.  During the first 72 hours, the
track guidance is tightly clustered near the new forecast track with
the notable exception of the GFDL model, which forecasts a track
near the Hawaiian Islands.  After 72 hours, the guidance has come
into better agreement that the subtropical ridge north of Hawaii
will be stronger than earlier forecast, and that Julio should
continue a west-northwesterly to westward motion.  This has reduced,
but not eliminated, the spread in the track guidance at 96 and 120
hours. The new track forecast is just south of the previous forecast
through 72 hours, then is adjusted farther south from the previous
track at the later forecast times. The new forecast lies near or
just to the north of the multi-model consensus and the center of the
guidance envelope.

The dynamical models forecast Julio to remain in a light vertical
wind shear environment during the next 2-3 days as the cyclone
passes over sea surface temperatures of 25C-26C.  All of the
intensity guidance forecasts a gradual weakening during that time,
and the intensity forecast follows this scenario.  The intensity
forecast becomes more uncertain after 72 hours as Julio starts
moving over warmer sea surface temperatures.  During this period,
the statistical guidance is forecasting a weaker storm than the
dynamical guidance, and the the large-scale models have some
disagreement on how much shear Julio will encounter.  The later part
of the forecast is nudged upward as a compromise between the two
model camps.  Overall, the new forecast lies close to the intensity
consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 16.9N 136.5W   90 KT 105 MPH
 12H  08/0000Z 17.3N 138.9W   90 KT 105 MPH
 24H  08/1200Z 17.8N 141.9W   85 KT 100 MPH
 36H  09/0000Z 18.5N 144.8W   80 KT  90 MPH
 48H  09/1200Z 19.3N 147.6W   70 KT  80 MPH
 72H  10/1200Z 21.5N 153.0W   60 KT  70 MPH
 96H  11/1200Z 23.5N 158.0W   55 KT  65 MPH
120H  12/1200Z 24.5N 162.0W   55 KT  65 MPH

$$
Forecaster Beven

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