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Potential Tropical Cyclone FOURTEEN-E


Potential Tropical Cyclone Fourteen-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP142017
300 PM MDT Tue Aug 29 2017

Satellite images indicate that the large disturbance southwest of
Mexico is gradually becoming better organized.  While the system
still lacks a well-defined center, all indications are that it will
become a tropical storm tomorrow.  Since the system is forecast to
bring tropical-storm-force winds to Baja California Sur within 36
hours, advisories are being initiated on a potential tropical
cyclone.  The system has 2-3 days over very warm water with
decreasing shear.  Although the system is quite broad for the
moment, the favorable environmental conditions noted above should
allow for at least steady strengthening.  Thus, the official
forecast is higher than the model consensus, but lower than the
bullish SHIPS model.

The initial motion is a highly uncertain 315/8.  A weak ridge over
central Mexico should steer the cyclone to the northwest or north-
northwest for the next few days.  Thereafter, the system should turn
toward the west-northwest as it moves around a stronger ridge over
the southwestern United States.  While there is some spread in the
guidance, the models are in reasonable agreement for a first
forecast, taking the system near or just west of Baja California
Sur.  The official NHC track prediction is between the model
consensus and the NOAA corrected-consensus model HCCA.

It is important to note that outside the watch/warning area, very
heavy rain is possible, which could cause life-threatening
flooding and mudslides over southwestern Mexico.  In addition,
wind gusts to tropical-storm force are possible along the coast of
Michoacan, Colima and Jalisco states tonight into early Wednesday
due to the large circulation.

The National Hurricane Center now has the option to issue
advisories, watches, and warnings for disturbances that are not yet
a tropical cyclone, but which pose the threat of bringing tropical
storm or hurricane conditions to land areas within 48 hours. Under
previous policy this was not possible.  These systems are known as
Potential Tropical Cyclones in advisory products and are numbered
from the same list as depressions.

Because of the threat to Baja California Sur, advisories have been
initiated on Potential Tropical Cyclone Fourteen-E and the
appropriate watches and warnings have been issued by the government
of Mexico.  Advisory packages will continue until the threat of
tropical-storm-force winds for land areas sufficiently diminishes,
although if the system becomes a tropical cyclone, the normal rules
for discontinuing advisories would apply.  Users should be aware
that forecast uncertainty for disturbances is generally larger than
for tropical cyclones, especially beyond 48-72 hours.


INIT  29/2100Z 17.2N 107.2W   25 KT  30 MPH...POTENTIAL TROP CYCLONE
 12H  30/0600Z 18.1N 108.0W   30 KT  35 MPH
 24H  30/1800Z 19.3N 108.9W   35 KT  40 MPH...TROPICAL STORM
 36H  31/0600Z 20.4N 109.8W   45 KT  50 MPH
 48H  31/1800Z 21.4N 110.4W   55 KT  65 MPH
 72H  01/1800Z 23.5N 112.0W   60 KT  70 MPH
 96H  02/1800Z 25.0N 114.0W   50 KT  60 MPH
120H  03/1800Z 26.5N 117.5W   35 KT  40 MPH

Forecaster Blake