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Eastern North Pacific Tropical Weather Discussion



589 
AXPZ20 KNHC 200325
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Jul 20 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. 

...TROPICAL WAVES...

A tropical wave is analyzed N of 07N along 99W moving W at 10 to 
15 kt. Scattered moderate isolated strong convection is noted 
from 12N to 14N between 95W and 103W.

A tropical wave is analyzed from 06N to 15N along 107W moving W 
at 15 kt. Scattered moderate isolated strong convection is noted 
from 07N to 09N between 105W and 112W.

A tropical wave is analyzed from 06N to 15N along 129W moving W 
at 15 kt. Scattered moderate convection from 08N to 12N between 
127W and 130W.

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

The monsoon trough extends across the entire basin from 09N78W 
to 10N112W to 12N128W to 11N140W. Scattered moderate isolated 
strong convection is noted from 07N to 10N east of 112W. 
Scattered moderate convection is noted from 08N to 14N between 
117W and 134W.  

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A surface ridge will persist from 31N134W to the Revillagigedo 
Islands for the next few days, maintaining gentle to moderate 
breezes across the Mexican offshore waters into early next week. 
Southerly cross-equatorial swell will propagate into the region 
by late Fri, allowing seas to build to 5 to 7 ft in open waters 
into early next week. 

In the Gulf of Tehuantepec, strong N gap wind flow will return 
late Sat, producing mixed seas south of the Gulf as wind waves 
generated near Tehuantepec encounter the longer period southerly 
swell. The gap winds will be due to lowering pressure south of 
the region along with localized drainage flow. 

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

Gulf of Papagayo: Fresh to strong nocturnal easterly winds, 
accompanied by 6 to 8 ft seas, are expected into early next week.

Gentle to moderate easterly winds are forecast elsewhere N of 
the monsoon trough which meanders between 07N and 10N. Moderate 
southerly winds are expected S of the trough axis for the next 
several days, accompanied by 4 to 6 ft seas.

Long period cross-equatorial southerly swell will continue to 
propagate N, reaching the far offshore waters between 05N and 
14N W of 86W Sun night, and the coast of Central America Mon.  

Looking ahead, global models are showing increased southwesterly
flow into the monsoon trough starting by mid week. Along with 
strong gap winds through the Gulf of Papagayo, this will help 
develop multiple low pressure areas along the monsoon trough in 
the offshore waters west of Costa Rica and Nicaragua. Expect 
increased showers and thunderstorms in this area into mid week.

REMAINDER OF THE AREA...   

A surface trough will move into the waters north of 27N between 
125W and 135W Fri through Sun, weakening the subtropical ridge, 
helping maintain moderate to fresh trade winds farther south.

Large long period southerly swell is moving across the equator 
between 90W and 125W, and will continue to propagate northward, 
affecting an area S of 17N between 80W and 133W by Sun night. 

Long period northerly swell will propagate into forecast waters 
N of 27N between 130W and 140W during the upcoming weekend, and 
then subside on Mon.  

$$
Mundell