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Eastern North Pacific Tropical Weather Discussion



352 
AXPZ20 KNHC 212151
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2150 UTC Fri Sep 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.

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

A segment of the monsoon trough extends from 10N85W to 12N110W 
to 11N120W. Another segment of the monsoon trough reaches from a 
1010 mb low near 15N126W to 11N140W. Scattered moderate convection
is noted from 12N to 15N between 95W and 100W. Scattered moderate
within 120 nm south of the monsoon trough axis between 130W and
138W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

A ridge will persisting from roughly 25N140W through the
Revillagigedo Islands into next week will support gentle 
northwest flow west of the Baja California through Sat, except 
becoming a moderate NW breeze within 90 nm of the coast during 
the late afternoons and evenings. A tightening pressure gradient 
Sat night through mid week will support moderate northwest flow 
west of Baja, except increasing to a fresh breeze during the 
evenings within 90 nm of the coast. 

Gulf of California: Gentle to locally moderate variable winds 
forecast across the gulf waters north of 30N through the 
upcoming weekend. Light to gentle variable winds expected south 
of 30N through the middle of next week.

Gulf of Tehuantepec: Fresh to locally strong nocturnal flow 
forecast to pulse through Tue, with longer lasting strong 
drainage flow then forecast for Tue night through Thu night with 
seas building to 8 ft.

Extended model guidance suggests a surface low will develop near 
12N103W on Sun night, and track northwest across the offshore 
waters seaward of 200 nm reaching near 17N109W on Wed.   

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

Gulf of Papagayo: Moderate to locally fresh east nocturnal 
drainage flow expected through Mon night. 

Light and variable winds are forecast elsewhere N of the monsoon 
trough which is meandering between 09N and 11N. Moderate 
southwest flow is forecast S of the monsoon trough through the 
middle of next week when long period southwest swell, in the 
form of 6 to 8 ft seas, will propagate northeast reaching the 
far offshore waters near 09N90W on Wed.  

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

REMAINDER OF THE AREA...   

A 1010 mb surface low analyzed near 15N126W will weaken into a 
trough by Sun, and move west of the area early next week.

A broad ridge continues across the subtropics with an area of 
fresh north winds and 7 to 8 ft seas forecast across the waters 
north of 28N between 123W and 129W through early this morning. 
Fresh northeast trades and diminishing across the waters from 12N
to 18N west of 135W.

$$
Christensen