000
AXPZ20 KNHC 211609
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Mon May 21 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 09N74W TO 12N97W TO 08N123W TO 
10N128W. The ITCZ extends from 08.5N135W to beyond 09N140W. 
Scattered moderate to strong convection is observed from 04.5N 
to 11N between the coast of Colombia and 105W, from 05N to 11N 
between 107W and 124W, and within 180 nm N of the ITCZ between 
134W and 140W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Overnight scatterometer data confirmed moderate to fresh NW 
winds continuing across the offshore waters of Baja California, 
where seas are running 6-7 ft. Winds freshen as the move across 
the Cabo San Lucas area, and are combining with the arrival of 
strong SW cross equatorial swell to produce seas of 7-8 ft from 
21N to 23N between Las Islas Tres Marias and 112W. This swell 
will penetrate southern portions of the Gulf of California today 
through Tuesday. Generally light to gentle variable winds are 
noted over the Gulf of California, except for moderate southerly 
winds across far north portions. Light NW to W winds continue 
farther south across the Mexican coastal waters. The main marine 
forecast issue for the next couple of days in the arrival of 
long period SW swell moving into all of the regional Pacific 
waters today through mid week. Large SW swell will raise seas in 
excess of 8 ft across the waters of southern Mexico later today, 
and the open waters off Baja California tonight and Tue, mixing 
with NW swell off Baja California Norte. Overnight altimeter 
data suggests that the largest and strongest swell is aimed for 
central Mexico between Tehuantepec and Mazatlan.

In the Gulf of Tehuantepec, light winds will persist into Tue,
then moderate to fresh gap winds will pulse briefly as sharp
troughing shifts slowly NW across southeast Mexico.

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

Gulf of Papagayo: Light to gentle winds will dominate the gulf 
the entire forecast period as elongated weak low pressure will 
prevail across Central America. Seas of 5-8 ft are forecast over 
the Gulf and nearby waters through mid week due to the strong 
long period SW swell arriving this morning.

Gulf of Panama: Gentle to moderate S to SW winds are forecast 
through Wed with seas of 4-6 ft in long period SW swell, 
building to 5-7 ft later today as the swell reaches the coasts 
of Panama and Colombia. 

Elsewhere, gentle to moderate SW winds are expected to the south 
of the monsoon trough with light to gentle variable winds north 
of trough as a weak pressure pattern remains over Central 
America. Seas of 6-9 ft in building long period SW swell west of 
the Galapagos Islands are expected to propagate northward 
tonight through late Tue next week, building to 8 to 11 ft to 
the west and northwest of the Galapagos Islands tonight through 
tonight.

Additionally, deep layered upper troughing extending from the 
Gulf of Mexico southward into the western Caribbean will drift 
westward and dig farther southward into Central America Wed and 
Thu. This may induce a broad low level cyclonic circulation 
across portions of the Yucatan and Central America, leading to 
periods of heavy rainfall across the region. This heavy rain 
could extend into the Pacific coastal zones of the region by the 
end of the week. 

REMAINDER OF THE AREA...

A ridge extends from 1026 high pressure centered near 31N141W 
through the Revillagigedo Islands. Overnight scatterometer data 
indicated fresh to strong trade winds from 10N to 22N west of 
130W, between the ridge and a weak trough along the ITCZ.
Elsewhere the ridge is maintaining generally moderate to fresh 
trades north of the monsoon trough and west of 120W. Convergence 
of these winds with light to moderate SW flow on the south side 
of the monsoon trough is supporting clusters of showers and 
thunderstorms near the monsoon trough west of 107W. Various 
overnight altimeter data also indicated 5 to 7 ft seas north of 
20N where winds are lighter, and 7 to 9 ft seas in the trade 
wind belt between the monsoon trough as far north as 17N as SW 
swell has begun to move into the region.

The ridge will build north of 20N through into mid week, 
enhancing trade winds especially near a developing weak low 
pressure along the monsoon trough near 10N125W. Various recent 
altimeter satellite passes continue to show SW swell in excess 
of 10 ft south of 10N, propagating northward. This will overtake 
the region east of 130W through Tue. Looking ahead, the upper 
pattern will amplify by mid week, supporting development of 
another weak low along the monsoon trough west of 125W. 

$$
Stripling