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TROPICAL STORM GUILLERMO DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092015
200 AM PDT THU JUL 30 2015

GOES satellite imagery show that the cloud pattern has become better
organized with numerous cyclonically curved convective bands around
the center of circulation. The upper-level outflow has improved
during the past several hours. Dvorak T-numbers are now 3.0 and
2.5 from TAFB and SAB, respectively. Thus, the depression has been
upgraded to Tropical Storm Guillermo with an initial intensity of
35 kt. Guillermo is the seventh tropical storm of the 2015 eastern
north Pacific hurricane season.

The environment of low shear and warm SSTs is quite favorable for
strengthening, and Guillermo will likely become a hurricane in about
36 hours. The probability of rapid intensification included in the
SHIPS guidance is 32 percent. After 72 hours, both cooler ocean and
increasing shear will likely induce gradual weakening. The NHC
forecast follows very closely the intensity consensus.

The best estimate of the initial motion is toward the west-
northwest or 285 degrees at 13 kt. Guillermo is well embedded within
the deep easterly flow south of a moderate subtropical ridge. There
is high confidence that this pattern should keep the cyclone on this
general track for the next 2 to 3 days, given that the guidance is
tightly clustered during that period. After that time, Guillermo
will reach the western edge of the ridge and will turn more to the
northwest toward a mid-latitude trough. The NHC track forecast is
similar to the previous one and is basically on top of the consensus
of the ECMWF and the GFS global models.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z  8.5N 126.3W   35 KT  40 MPH
 12H  30/1800Z  8.9N 128.2W   45 KT  50 MPH
 24H  31/0600Z 10.1N 131.1W   55 KT  65 MPH
 36H  31/1800Z 11.2N 134.2W   65 KT  75 MPH
 48H  01/0600Z 12.2N 137.4W   75 KT  85 MPH
 72H  02/0600Z 14.5N 141.6W   70 KT  80 MPH
 96H  03/0600Z 16.3N 144.3W   65 KT  75 MPH
120H  04/0600Z 18.0N 146.5W   55 KT  65 MPH

$$
Forecaster Avila

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