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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

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