AXPZ20 KNHC 211503
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1503 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
Based on 1200 UTC surface analysis and satellite imagery through
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 10N85W to 12N110W to 11N120W.
Another segment of the monsoon trough reaches from a 1010 mb low
near 16N125W to 10N140W. Scattered moderate to isolated strong
convection is noted within 270 nm off the coast of Central
America and southern Mexico from 10N to 20N, and within 180 nm
of the coast of Colombia. Scattered moderate convection is noted
within 90 nm of the monsoon trough between 133W and 138W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
A ridge will meander from 22N116W to 14N97W through early next
week. Gentle northwest flow is forecast 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 on Sat night through
Tue will support moderate northwest flow west of Baja, except
increasing to a fresh breeze during the evenings within 90 nm of
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 through Tue, with 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 is analyzed near 16N125W and is
accompanied by scattered moderate isolated strong convection
northwest of the low within 60 nm of 16N124W. The surface low
will weaken into a trough by Sun, and move west of the area early
A broad ridge continues across the subtropics with an area of
fresh north winds and 7 to 9 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.