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Eastern North Pacific Tropical Weather Discussion



826 
AXPZ20 KNHC 231603
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Mon Jul 23 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 1200 UTC surface analysis and satellite imagery through
1545 UTC.

...TROPICAL WAVES...

A low-latitude tropical wave has its axis along 84W from 01N to
12N, moving westward at 15 to 20 kt. The wave remains evident in
tropical wave model diagnostics as well as a maximum in total 
precipitable water satellite imagery. Scattered moderate isolated
strong convection is within 180 nm east of the wave from 09N-
12N, including sections of Costa Rica and northern Panama.
Stronger convection has raced westward out of this wave, but is 
mainly related to the monsoon trough as described below.

A tropical wave has its axis extending from 02N99W to 11N98W 
to 16N96W, moving westward at about 20 kt. The wave is evident 
in 700 mb model guidance streamlines as well as a pronounced 
maximum in total precipitable water satellite imagery. Numerous 
strong convection is within 30 nm of 15N100W. Scattered moderate
isolated strong convection is within 30 nm of line from 08N97W 
to 11N99W. Scattered moderate convection is within 30 nm of
12N96W.

A tropical wave has its axis extending from 04N127W to a 1010 mb 
low near 11N127W and to 17N127W, moving westward at 15-20 kt.
The wave is associated with broad troughing at 700 mb as 
depicted in model guidance. Scattered moderate isolated strong 
convection is within 150 nm of the low in the SW quadrant and 
within 90 nm of the low in the NW quadrant. Scattered moderate 
convection is within 120 nm of the low in the SE quadrant and 
also within 60 nm of the low in the NE quadrant.

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

The monsoon trough axis extends from a 1010 mb low over NW 
Colombia near 09N74W to Costa Rica near 10N83W to 09N94W to
10N108W to 11.5N121W to low pressure near 11N127W to 10N134W and 
to west of the area at 12N140W. Aside from convection associated
with the tropical waves, scattered moderate to strong convection
is within 120 nm north of the axis between 110W-114W, and within 
60 nm either side of the axis between 87W-91W. Scattered 
moderate isolated strong convection is south of the axis within 
30 nm of a line from 08N130W to 08N135W, and from 06N-10N west of
136W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A broad and weak high pres ridge extends SE from 32N140W
east-southeastward to the Revillagigedo Islands near 16N107W. 
The ridge is maintaining light to moderate NW winds across the 
Mexican offshore waters, except for the Gulf of Tehuantepec area 
as 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 20N. This extensive swell 
event will continue spreading northward, and will cause seas to 
build to the range of 7 to 9 ft in the open waters for all the 
forecast zones through Tue night before they begin to slowly
subside through the rest of the week.

Gulf of Tehuantepec: fresh to strong north winds will diminish 
to the light to moderate range early this afternoon, then become
gentle S to SW tonight and then gentle to variable Tue. Wind 
waves generated by the north winds are interacting with the SW 
swell event resulting in mixed seas to the south of the Gulf, 
with sea heights ranging between 8-9 ft. These seas will merge 
with the much larger area of 8 ft seas approaching from the
S this evening, and gradually subside Tue and Wed.

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

Gulf of Papagayo: Fresh to strong NE to E winds will pulse 
during the late night and morning hours through Wed morning 
before diminishing to fresh intensity. Ship with call sign
"DDVK2" reported NE winds of 25 kt at just after 12Z this morning 
near 11N89W. Seas from these NE to E winds will interact with 
the SW swell event to produce mixed seas in the Gulf as high as 
high as 10 ft today before seas begin to slowly subside on Tue.

Gentle to moderate NE to E winds 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 has engulfed just
about the entire region. Maximum wave heights with this event 
are near 10 ft south of 06N between 82W-90W. Wave model 
guidances suggest that seas will gradually subside to 8 ft Wed, 
and to less than 8 ft Thu.

REMAINDER OF THE AREA... 

A weak surface ridge extends into the discussion area at 
32N140W, and continues east-southeastward to 25N118W and to the 
Revillagigedo Islands near 16N107W. The gradient between the 
ridge and lower pressure found along and near the monsoon trough 
is maintaining mainly fresh northeast to east trade winds north 
of the monsoon trough, south of 20N and west of 115W. Little 
change in this pattern is expected for the upcoming week. Swell 
generated by strong winds north of the area is propagating 
southward inducing seas to build to 8 ft in the discussion waters
N of 28.5N and W of 133W. This swell will decay through this 
evening allowing for seas to subside to less than 8 ft.

Low pressure of 1010 mb is located near 11N along the tropical 
wave that extends from 04N127W to 17N127W. The low will generate
fresh to strong winds over the waters within 180-240 nm to its
north as it tracks in a westward to west-northwestward motion 
reaching near 12N138W by Wed morning. The low should cross 140W 
near 12N late on Wed. Seas in the range of 8-10 ft are expected 
with its associated winds. Lingering mixed swell will produce 
seas of 8-9 ft over the far western waters on Thu from about 
12N-19N and west of about 135w.

Large long-period SW swell is crossing the equator, with seas of
8 to 11 ft affecting almost all of the waters S of 20N as 
confirmed by satellite-derived sea height data. Wave model
guidances indicate that the swell will slowly dissipate through 
Wed allowing for seas to subside to 8 ft or less.

$$
Aguirre