Skip Navigation Links
NOAA NOAA United States Department of Commerce

Eastern North Pacific Tropical Weather Discussion



504 
AXPZ20 KNHC 220400
TWDEP 

Tropical Weather Discussion 
NWS National Hurricane Center Miami FL
0405 UTC Sat Sep 22 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 0000 UTC surface analysis and satellite imagery through 
0300 UTC.

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

The monsoon trough extends W off the Caribbean coast of Colombia 
at 10N75W, and continues west across the extreme southwest 
Caribbean and across northern Costa Rica to the Pacific Coast of 
Costa Rica at 11N85W to 09N104W TO 14N125W where it loses 
identity in the cyclonic circulation associated with a 1010 mb 
surface low at 15N127W. The monsoon trough resumes southwest of 
the low at 14.5N129W and continues southwest to 13N140W. 
Isolated moderate and strong convection is noted within the area 
bounded by 19N108W to 12N90W to 04N90W to 06N120W to 19N108W. 
Scattered moderate isolated strong convection is observed within 
150 nm either side of a line from 11N130W to 09N140W. Scattered 
moderate isolated strong convection is noted within 30 nm either 
side of lines from 07N81W to 10.5N86W and from 15.5N97W to 
17N101W, and within 45 nm of 21N105.5W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

A ridge extending from 22N116W to 15N100W will gradually retract 
northwest as a surface low slowly develops near 13N106W on Sun 
night, and then tracks northwest accompanied by tstms just 
beyond 250 nm seaward. However, moderate cyclonic winds will 
shift northwest through the offshore waters seaward of 200 nm 
with the low reaching a position near near 15.5N109.5W on 
Wed and near 18N115W on Fri.

Moderate northwest flow is forecast west of the Baja California 
through early Mon, except becoming a fresh northwest breeze 
within 90 nm of the coast during the late afternoons and 
evenings.  

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

Gulf of Tehuantepec: Fresh to locally strong nocturnal flow 
forecast on Sat night through Mon night, with a strong northerly
drainage event expected on Thu night with seas building to 9 ft.
The late week event may assist in the development of a surface
low near 12N95W late next week.  

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. Moderate to fresh southwest monsoonal flow 
is expected south of 10N late next week as a surface low begins
to develop near 13N93W on Thu, and then tracks northwest of the
area on Fri accompanied by tstms.   

REMAINDER OF THE AREA...   

A 1010 mb surface low is analyzed near 15N127W with a low level 
trough extending northeast to near 20N122W with isolated strong 
convection flaring within 60 nm of the trough.  The surface low 
will weaken to an inverted trough this weekend, and move west of 
the area by the middle of next week.

A broad ridge continues across the subtropics accompanied by 
moderate to locally fresh anticyclonic flow south of 23N west of 
120W.

$$
Nelson