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Eastern North Pacific Tropical Weather Discussion



794 
AXPZ20 KNHC 220837
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
641 UTC Sun Jul 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 0600 UTC surface analysis and satellite imagery through
0815 UTC.

...TROPICAL WAVES...

A low latitude tropical wave over Colombia has an axis from 
00N74W to 11N74W, moving westward between 15 and 20 kt. The wave 
is evident in tropical wave model diagnostics as well as a 
maximum in total precipitable water satellite imagery. Scattered 
moderate and isolated strong convection is noted N of 05N 
between 83W and 94W.

A tropical wave has an axis from 06N87W to 22N86W, moving 
westward around 10 kt. The wave is evident in 700 mb model 
guidance streamlines as well as a maximum in total precipitable 
water satellite imagery. Scattered moderate and isolated strong 
convection is noted N of 05N between 83W and 94W.

A tropical wave has an axis from 05N118W to 17N117W, moving 
westward around 20 kt. The wave is associated with troughing at 
700 mb in model guidance as well as a maximum in total 
precipitable water satellite imagery. Scattered moderate and 
isolated strong convection is present from 08N to 13N between 
122W and 126W.

A tropical wave has an axis from 02N126W to 14N125W, moving 
westward around 15 kt. The wave is weak, but can be tracked via 
subtle 700 mb troughing in model guidance. Scattered moderate 
convection is observed from 07N to 13N between 122W and 126W.

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

The monsoon trough extends from 10N76W to 07N91W to 11N108W to 
10N117W. Aside from convection associated with the tropical 
waves, scattered moderate and isolated strong convection is found
within 90 nm of a line from 07N96W to 10N106W. A 1008 mb surface
low is centered near 13N136W. Numerous moderate and scattered 
strong convection is occurring within 60 nm of 13.5N136W. 
Scattered moderate convection is present from 07N to 11N W of 
135W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A surface ridge extends SE from weak 1017 mb high pres centered 
near 25N123W to ESE of the Revillagigedo Islands near 16N106W. 
The ridge is maintaining light to moderate NW winds across the 
Mexican offshore waters, except for the Gulf of Tehuantepec 
discussed below. Little change is expected in these conditions 
during the next several days. A long period SW cross-equatorial 
swell is affecting the waters S of 15N. This extensive swell 
event will continue spreading N and will cause seas to build to 
between 7 and 9 ft in the open waters for all the forecast zones 
through early next week.

In the Gulf of Tehuantepec, pulses of fresh to strong N gap 
winds will occur during the late night and morning hours until 
Mon morning. Wind waves generated by these N winds will interact 
with the SW swell event to produce mixed seas south of the Gulf 
peaking near 10 ft on Sun before winds subside on Mon morning. 
Seas near the Gulf of Tehuantepec will remain above 8 ft until 
Wed morning as SW swell continue to arrive.

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

Gulf of Papagayo: Fresh to strong easterly winds will pulse 
during the late night and morning hours through Tue morning, then
winds during this time frame will taper to fresh. Seas from 
these NE to E winds will interact with the SW swell event to 
produce mixed seas SW in the Gulf as high as 10 ft on Mon before 
seas begin to subside on Tue.

A low latitude tropical wave currently over Colombia could reach
the waters W of Colombia by this evening. This feature is 
already triggering showers and thunderstorms S of Panama and W of
Colombia.

Easterly winds of only moderate speeds or weaker are forecast 
elsewhere N of the monsoon trough which will meander west of 
Central America between 07N and 10N. Moderate to fresh S to SW 
winds are generally expected S of the trough axis during the next
several days.

A long-period SW cross-equatorial swell event is already 
affecting the region as seas S of the equator have risen to 9 
ft. Seas will peak between 8 and 10 ft on Mon in the open waters,
with the highest seas expected W of Ecuador.

REMAINDER OF THE AREA...   

A broken surface ridge hangs on from 32N140W to 23N132W, then to
weak 1017 mb high pres centered near 25N123W. The ridge is
generally maintaining mainly moderate trade winds N of the 
monsoon trough, S of 20N and W of 115W. Little change in this 
pattern is expected for the next several days. Swell to 8 ft 
generated by strong winds N of the area is propagating S to cover
the discussion waters N of 29N between 130W and 138W. This swell
will continue to affect this region while slowly shifting 
westward through Mon.

A 1008 mb area of low pressure is centered near 13N138W. Fresh 
to strong winds are occurring within about 300 nm N of the low 
center with associated seas to 10 ft. Numerous moderate and
scattered strong convection is occurring within 60 nm of
13.5N136W. Scattered moderate convection is present from 07N to 
11N W of 135W. This low and associated conditions will move W of
the discussion area by Mon morning.

Large long period SW swell is crossing the equator, with seas of
8 to 10 ft extending from the Southern Hemisphere northward to a
line from 03.4S83W to 00N86W to 12N103W to 14N123W to 04N137W, 
as confirmed by recent satellite-derived sea height data. The 
swell will continue to propagate N and cause seas to build to 8 
ft or above to most of the area S of 25N and east of 133W Mon, 
before the swell decay and seas subside on Tue.

$$
CAM