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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 260231

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 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 0000 UTC surface analysis and satellite imagery through 
1300 UTC.


The remnants of Tropical Depression Pilar has dissipated along 
the Mexican coast near 23.9N106.9W, were an isolated cluster of 
heavy showers and thunderstorms continues tonight. A trough of 
low pressure extends from this area WSW to near Cabo San Lucas 
in Baja California Sur. Along and to the south of this trough, 
westerly winds of 15 to 20 kt are found across the entrance to 
the Gulf of California with seas 5- 6 ft. Low level moisture 
will linger along the western slopes of the Sierra Madre 
Occidentales and the coastal zones from Guadalajara to central 
Sinaloa through Tue to produce scattered showers and 
thunderstorms, some yielding very heavy rain. 


The monsoon trough axis extends from 09N72W TO 15N96W TO 13N105W 
TO low pressure near 13N124.5W 1008 MB TO beyond 11N140W. 
Scattered moderate to strong convection is from 04N to 14.5N E 
of 95W, from 10N to 14N between 95W and 106W, and from 90 nm N 
to 150 nm S of the trough between 123W and 140W.



As described above, wind and seas associated with the remnants 
of Pilar have subsided to 20 kt or less and 6 ft or less between 
the entrance to the Gulf of California and Las Tres Marias, and 
will slowly diminish further late tonight through Tue.

A high pressure ridge reaches SE into the waters west of Baja 
California to near 19N116W, with the associated pressure 
gradient expected to maintain moderate NW winds along the 
Pacific coast of Baja tonight. The ridge will weaken in response 
to low pressure passing well to the north and NW winds will 
become gentle to moderate Tuesday through Thursday night. Fresh 
SW to W monsoonal winds well offshore of the Gulf of Tehuantepec 
will generate SW wind waves in the SE waters and maintain seas 
in this area of 5 to 7 ft.


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. Active convection will prevail across the 
regional waters for the next few days.

Long period SE to S swell will decay and allow seas west of 
Ecuador and south of the Equator to subside from around 6 ft to 
around 5 ft during the next couple of 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.

Fresh to strong winds occurring around low pressure embedded in 
the monsoon trough near 13N124.5W are supporting a surrounding 
area of 8 to 11 ft seas in mixed swell. Fresh to strong winds 
extend farther E to near 120W there, where seas are 8-9 ft. 
Monsoonal SW winds will remain fresh to strong across this 
general area between 09N and 14N through Wed and maintain seas 8-
9 ft. 

Otherwise, high pressure centered well N of the area, and low 
pressure associated with the monsoon trough will maintain 
moderate to occasionally fresh trade winds W of 120W through 
tonight. Low pressure passing north of the area will weaken the 
high, allowing trades to decrease for the remainder of the week.