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Eastern North Pacific Tropical Weather Discussion



193 
AXPZ20 KNHC 201538
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1537 UTC Thu Sep 20 2018

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. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough extends from 09N84W to low pressure near
09N87W 1006 mb, to 12N100W to 10N117W. Another segment of the
monsoon trough continues from 1009 mb low pressure near 15N123W
to 09N140W. Scattered moderate convection from 11N to 15N between
97W and 102W, and from 07N to 12N between 110W and 113W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

The remnant low of of Tropical Depression Nineteen-E well inland
over the Mexican state of Sonora, near 28.5N110W. Fresh onshore 
winds continue to support showers and thunderstorms over the 
mountains, with the heaviest activity currently ongoing in the 
northern portions of Sinaloa, between Culiacan and Los Mochis. 
Life-threatening flash floods and landslides are possible through
the afternoon. For the marine areas over the southern Gulf of 
California, a recent altimeter pass indicated seas have subsided 
since yesterday, with seas 2 to 4 ft. 

Elsewhere north of 20N, moderate to fresh NW winds persist off 
the Pacific coast of Baja California, funneling between the 
coastline and 1026 mb high pressure well northwest of the area. A
satellite altimeter pass from 11 UTC showed seas approaching 8 
ft north likely due to NW swell entering the discussion area 
north of 29N and west of 116W. While this is expected to decay 
below 8 ft today leaving mainly 5 to 7 ft seas, the NW swell and 
local wind waves will interact with southerly swell off the coast
Baja California over the next several days. 

Farther south, strong winds into the Gulf of Tehuantepec are
diminishing. These were evident in an evening scatterometer
satellite pass. The winds are the result of a fairly tight
gradient due to enhanced troughing over the southwest Gulf of
Mexico. A weaker and short-lived pulse of strong winds is
possible tonight in the Gulf of Tehuantepec. Looking ahead,
another strong pulse of gap winds is possible late Sat into
early Sun ahead of a tropical wave moving through Central
America and southern Mexico. 

Looking further ahead, there is growing consensus among major
models of weak low pressure forming by late Mon into early Tue
around 240 nm southwest of Manzanillo and 240 NM southeast of 
Socorro Island.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND 
WITHIN 750 NM OF ECUADOR...

Fresh offshore nocturnal winds will pulse across the Gulf of 
Papagayo the next several nights. Cross-equatorial SW swell 
reaching the Central American coast will slowly subside this 
weekend. The monsoon trough will meander near 10N the next few 
days.

Looking ahead, an increase in moist southwest flow is advertised
by the major global models by early next week, possibly
culminating in a Central American gyre pattern by mid week. This
may bring increase showers and thunderstorms to the Pacific
waters off Central America by early next week, and possibly
increased winds and seas thereafter.

REMAINDER OF THE AREA...   

An elongated surface trough extends from roughly Clarion Island
to 1009 mb low pressure near 15N123W. Surface ridging prevails 
over the waters NW of the trough axis. Moderate to locally fresh 
trades are north of the trough west of 120W, supporting seas to 8
ft from 14N-19N W of 130W. These seas will subside during the 
next 2 days as the pressure gradient weakens.

$$
Christensen