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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 171535

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1402 UTC Fri Nov 17 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.


The monsoon trough extends from 09N83W to 10N90W to 08N100W TO
09N125W where it transitions to the intertropical convergence 
zone, and extends from 09N125W to 11N136W to beyond 08N140W. 
Scattered moderate convection is noted from 08N to 12N between 
114W and 123W. Similar convection is from 12N to 15N between 
134W and 136W.



A weak 1018 mb surface high centered near 25N124W is forecast to
dissipate within 24 hours. This system will be reinforced by a 
stronger high pressure from the N on Sat. Under this weather 
pattern, expect gentle to moderate northerly winds across the 
offshore waters W of Baja California today, with moderate to 
fresh NW to N flow, and building seas of 6-7 ft N of 25N Sat 
morning through late Sun.

Gulf of Tehuantepec: Pulses of strong to near gale force 
northerly drainage flow, with seas building to a max of 11 ft, 
are forecast late tonight into early Sat morning, diminishing 
afterward as the high pressure over the eastern slopes of the 
Sierra Madre mountains weakens. Another strong cold front will 
enter the Gulf of Mexico late Sat, followed by strong high 
pressure building into northeast and central Mexico through Sun. 
This will support a return of strong gap winds in the Gulf of 
Tehuantepec by early Sun, reaching gale force early Sun afternoon
through Mon morning. Marine guidance indicates winds of 35-40 kt
and building seas of 14-15 ft by Sun night. 

Gulf of California: Strong high pressure building north of the 
area over the Great Basin will support fresh to strong NW winds 
across the northern Gulf of California by mid-day Sat, spreading 
into the central and southern portions of the gulf late Sat into 
Sun, before diminishing late Sun. Seas are forecast to build to 6
or 7 ft across the central gulf early on Sun.


Gulf of Papagayo:  Moderate to locally fresh NE drainage winds 
are forecast during the overnight hours through the middle of 
next week with seas building to 5 ft downstream near 10N87W. 

Light and variable winds, and 3 to 5 ft seas, are expected 
elsewhere to the N of 09N, while moderate to locally fresh 
southerly winds, and 4 to 7 ft seas, are forecast S of 09N 
through the middle of next week. 


A 1015 mb occluded surface low is centered near 29N132W. The 
associated cold front enters the forecast waters near 30N128W 
and extends to 20N135W. An earlier ASCAT pass indicated fresh to 
strong N winds within about 120 NM in the NW quadrant of the 
low center. A pair of altimeter passes showed 8 to 10 ft seas in
the wake of the front. The low is forecast to move near 28N132W 
within the next 12 hours while weakening significantly. The front
will become stationary later today and gradually dissipate tonight
into Sat. 

Strong SE to S return flow will develop across the NW waters N 
of 27N W of 138W by Sat night, in advance of the next cold front
forecast to approach the far NW corner of the area Sun night. 
The front will move slowly with the strong S to SW flow persisting
over the NW waters on Mon. At that time, expect fresh to strong 
winds and seas of 8 to 10 ft covering roughly the waters N of 24N
W of 136W.

Farther S and N of the ITCZ/Monsoon trough, expect gentle to 
moderate trade winds and 4 to 6 ft seas through Sat, with moderate
to fresh trades and seas of 6 to 8 ft by Sat evening into Sun.