000
WTPZ42 KNHC 212034
TCDEP2

TROPICAL STORM FRANK DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072016
400 PM CDT THU JUL 21 2016

A 1600 UTC ASCAT-B scatterometer pass indicated that the weather
system located off the coast of Mexico has developed a well-defined
center of circulation, and maximum winds were around 40 kt.  Based
on these data, advisories are being initiated on Tropical Storm
Frank, the sixth tropical storm to form in the eastern Pacific this
month.  Frank currently has broken convective outer banding, but a
burst of convection is developing near the estimated center.

With the recent formation, the initial motion is somewhat uncertain
but is estimated to be northwestward, or 305/12 kt.  Frank is
located to the south of a large and strong mid-level anticyclone
which is centered over the Southern Plains of the United States.
Although ridging will remain across the southern U.S. and northern
Mexico, the main center of the anticyclone is expected to migrate
westward over the Pacific Ocean during the next 48 hours, leaving a
minor break in the ridge near the Baja California peninsula.  As a
result, Frank is expected to maintain a northwestward heading for
the entire forecast period but with a gradual decrease in forward
speed.  There is a normal amount of spread in the track guidance,
and the initial NHC forecast is very near the various multi-model
consensus aids.  Although the track is currently off the coast of
Mexico, there is still enough uncertainty that interests in the
southern portion of the Baja California peninsula should monitor
the progress of Frank.  In fact, based on the wind speed
probabilities, there is currently a 1-in-4 chance of tropical storm
force winds affecting locations in extreme southern Baja California
Sur during the next 5 days.

Frank is currently over warm SSTs over 29C, and waters are expected
to remain warm for the next four days or so.  Although some
vertical shear could persist for much of the forecast period, the
statistical-dynamical guidance and the HWRF show fairly quick
strengthening over the next few days.  The NHC intensity forecast
follows suit and is near the higher end of the guidance, making
Frank a hurricane in about 36 hours.  Some weakening is anticipated
after day 3 due to cooler waters and the possible continued shear.


FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 14.9N 104.0W   40 KT  45 MPH
 12H  22/0600Z 16.0N 105.4W   50 KT  60 MPH
 24H  22/1800Z 17.2N 107.1W   60 KT  70 MPH
 36H  23/0600Z 18.2N 108.6W   65 KT  75 MPH
 48H  23/1800Z 19.1N 110.0W   70 KT  80 MPH
 72H  24/1800Z 20.8N 112.2W   70 KT  80 MPH
 96H  25/1800Z 22.3N 113.7W   65 KT  75 MPH
120H  26/1800Z 23.5N 115.2W   55 KT  65 MPH

$$
Forecaster Berg