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Eastern North Pacific Tropical Weather Discussion



894 
AXPZ20 KNHC 210835
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
612 UTC Tue Aug 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 0600 UTC surface analysis and satellite imagery through
0800 UTC. 

...TROPICAL WAVES...

A tropical wave along 97W-98W is moving W around 15 kt. 
Scattered moderate and isolated strong convection is present from
06N to 12N between 94W and 101W. 

A tropical wave along 116W-117W is moving W around 10 kt. 
Scattered moderate and isolated strong convection is found from 
07N to 14N between 110W and 121W.

A tropical wave along 129W-130W is moving W around 5 kt. 
Scattered moderate and isolated strong convection is seen from
15N to 17N between 124W and 131W.

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

The monsoon trough extends from low pres 1010 mb near 10N74W to 
09N88W to 12N118W to 13N127W. The ITCZ continues from 13N127W to 
13N136W to beyond 12N140W. Scattered moderate and isolated strong
convection is observed from 08N to 11N between 101W and 107W, 
from 08N to 12N between 122W and 124W and from 07N to 12N W of 
133W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

A surface ridge across the NE Pacific extends SE from a 1028 mb 
high centered near 44N139W to enter the forecast waters near 
32N131W, then onward to near the Revillagigedo Islands. This 
ridge will support a weak to modest pressure gradient across the 
offshore waters of Baja California. Gentle to moderate NW winds 
are expected through Wed before the ridge strengthens slightly 
and the pressure gradient tightens across Baja California Norte 
Thu and Fri. Seas will generally remain in the 4-5 ft range 
through Wed. Surface troughing over the Baja Peninsula will 
maintain a generally light wind regime over the Gulf of 
California through Sat night, and allow for afternoon sea breezes
and nocturnal land breezes to dominate.

Strong N to NE gap winds will affect the Gulf of Tehuantepec 
tonight through Thu night, and are forecast to peak near 30 kt 
late Wed night. Seas of 4 to 6 ft during the daytime could build 
to near 8 ft each of these nights, and 8-10 ft late Wed night.

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

The monsoon trough will linger near 09N during the next few 
days. Winds on both sides of the trough axis will generally be 
light to moderate. The main exception to this will be over the 
Gulf of Papagayo, where moderate to fresh offshore winds will 
pulse to locally strong each night. Seas are expected to remain 
6-7 ft downstream of Papagayo during this time.

REMAINDER OF THE AREA...   

Elsewhere, the pressure gradient between ridging across the 
northern waters and the ITCZ will support gentle to moderate 
trades and 4-7 ft seas in mixed swell N of the ITCZ and W of 
120W through the middle of this week.

Sea heights will be relatively low for most of the forecast area
this week. Mixed SE and SW swell that produced 8 ft seas S of 
02S and W of 112W have subsided. This has allowed seas in this 
area to subside to less than 8 ft. A much more robust round of 
long period swell could arrive from the Southern Hemisphere 
toward the end of this week and cause seas near the Equator to 
begin building on Sat.

$$
CAM