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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 260952

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
635 UTC Tue Sep 26 2017

Tropical Weather Discussion for the eastern Pacific Ocean from
the Equator to 32N, east of 140W. The following information is
based on satellite imagery, weather observations, radar, and
meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0830 UTC.


The remnants of Tropical Depression Pilar in the form of a small
cluster of weak convection are located about halfway between 
Mazatlan and Culiacan Mexico near 24N107W. A residual trough of 
low pressure lingering in the wake of Pilar extends from near 
Cabo San Lucas in Baja California Sur to near Mazatlan Sinaloa. 
Surface observations and initial model wind fields both suggest 
winds in this area are 15 knots or less. Seas in the 4 to 6 ft 
range near the mouth of the gulf of California should subside to 
between 2 and 4 ft by Wednesday afternoon. Low level moisture 
still pooling along the western slopes of the Sierra Madre 
Occidental and the coastal zones from Guadalajara to central 
Sinaloa through tonight will produce scattered showers and 
thunderstorms, some yielding very heavy rain. 


The monsoon trough axis extends from 11N72W to 09N80W to 17N93W 
to 13N103W to low pressure near 13.5N124.5W 1008 MB to 10N133W to
beyond 11N140W. Scattered moderate and isolated strong 
convection is present in an area bounded by 09N83W to 05N89W to 
10N107W to 16N94W to 09N83W and within 90 NM either side of the 
trough axis between 119W and 128W.



As described above, winds and seas associated with the remnants 
of Pilar have subsided to 15 kt or less and 6 ft or less, 
respectively over the southern Gulf of California. Winds and seas
will continue to diminish through tonight. Light to gentle winds
are then expected to prevail over the southern Gulf of 
California through Fri. Winds will be gentle to moderate over the
northern Gulf of California during the same time frame.

A weakening high pressure ridge reaches SE into the waters west 
of Baja California to near 20N118W. The weakened pressure 
gradient on the east side of the ridge will maintain light to 
moderate NW winds along the Pacific coast of Baja through Thu 
night. The ridge will remain weaken as low pressure passes well 
to the north. Fresh SW to W monsoonal winds well offshore of the 
Gulf of Tehuantepec will generate SW swell and wind waves which 
will maintain seas of 5 to 7 ft in this area.


An active monsoon trough along and inland of the coasts of 
Central America from Guatemala to Panama will remain the focus 
for active convection over the coastal waters the next few days. 
Expect moderate SW to W winds to prevail south of the trough, 
with gentle to moderate variable winds north of the trough 
through Friday night. Winds will freshen in this region over the 
weekend in response to a developing area of low pressure over 
Central America. Active convection will prevail across the 
regional waters for the next few days.

Long period SE to S swell will maintain 5 to 6 ft seas west of 
Ecuador and south of the Equator during the next few days.


NW to N swell generated by strong winds north of the area are 
producing 6 to 7 ft seas N of 20N and W of 120W. Pulses of 
reinforcing N swell will maintain seas in the region between 6 
and 8 feet through Wed night, then seas will subside.

Fresh to strong winds occurring around low pressure embedded in 
the monsoon trough near 13N124.5W are supporting an associated 
area of 8 to 11 ft seas in mixed swell. Mixed swell are 
maintaining seas of 8 to 9 ft from 10N to 16N between 120W and 
128W. Monsoonal SW winds will remain fresh to strong across this 
general area through Wed, then subside.

Otherwise, weakened high pressure centered well N of the area 
and low pressure associated with the monsoon trough will maintain
light to moderate trade winds W of 120W through Fri night.