AXPZ20 KNHC 231603
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
Based on 1200 UTC surface analysis and satellite imagery through
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
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
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
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.