AXPZ20 KNHC 132209
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Thu Dec 13 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 1800 UTC surface analysis and satellite imagery through
Gulf of Tehuantepec Gale Warning: A cold front forecast to enter
the NW Gulf of Mexico this evening will initiate gale to strong
gale force winds across the Gulf of Tehuantepec by Fri evening
and is then expected to persist through the upcoming weekend and
beyond. Computer model guidance suggests that this long lived
gale event will last until Mon afternoon. Peak winds are
forecast to be 40 kt on Sat as corresponding seas quickly
building to near 18 ft. The first blast of strong northerly
winds associated with this event is expected to start during
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 09N75W TO 03.5N78.5W TO 08.5N85W
TO 05N102W. The ITCZ continues from 05N102W TO 08.5N118W TO
10N134W to beyond 07N140W. Scattered moderate to strong
convection is observed from 01.5N to 05.5N to the east of 85W,
while scattered moderate convection is observed from 04.5N to
07N between 92W and 102W. An upper level trough across far NW
portions of the area is creating a large area of overcast middle
and high level clouds, and scattered light to moderate elevated
convection from 15N to 22N between 120W and 136W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
Over the open waters off Baja California, another pulse of NW
swell is expected to reach Baja California Norte and Guadalupe
Island tonight. This latest round of swell will propagate SE and
cause seas to build to between 7 and 11 ft for the offshore
waters along the length of the Baja Peninsula by Fri afternoon.
A cold front approaching 30N140W late tonight will introduce
more long period NW swell to Baja Waters by Sun morning and
maintain sea heights at 7-9 ft through Mon morning. Looking
ahead, a much stronger cold front will reach Baja California
Norte by Mon night. Strong winds associated with this front
could brush 30N as the front crosses 30N140W. Long period NW
swell of 10-18 ft will enter the waters adjacent to Baja
California Norte during this time frame. Swell of this size and
period will present hazard seas for mariners as well as cause
very powerful and dangerous surf along the Pacific Beaches.
Strong high pressure building over the Great Basin will support
the development of fresh to strong winds over the Gulf of
California between 25N and 29N this afternoon through Fri
morning. seas could approach 8 ft over the southern Gulf
tonight. Winds and seas will subside through Sat as the high
pressure shifts eastward.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
Gulf of Papagayo...Strong gap winds have tapered off today but
will return during the overnight and early morning hours Sat
night, then persist through Mon night as high pressure builds
north of the region. Seas are expected to max out around 10 ft
Gulf of Panama...Fresh northerly winds across and downstream of
the Gulf have begun to back to the NW this afternoon and will
slowly diminish through Sat.
Elsewhere, gentle to moderate winds will persist on either side
of the monsoon trough through the remainder of the week, with
seas remaining in the 4-6 ft range.
REMAINDER OF THE AREA...
A large area of mixed seas persists over much of the north
Pacific between 95W and 120W. This area consists of NE and E
swell generated by recent Central American gap wind events,
merging with longer period NW swell. Maximum combined sea
heights in this area are 10 ft. This area of 8 ft seas will
vanish by late tonight as these swell decay.
Farther west, a persistent surface trough extends from 08N139W
TO 16N134W. The gradient between this trough and high pressure
north of the region is supporting strong trade winds from 15N to
20N between 125W and 140W. Recent satellite-derived wave height
data indicate seas as high as 13 ft. The high will weaken today
ahead of an approaching cold front, allowing the trade winds to
diminish by Fri morning.
A cold front will reach from 30N135W to 28N140W by early Fri,
and be accompanied by a new round of NW swell of 12 to 15 ft.
The front will dissipate later on Fri, with the swell subsiding
as well. Elsewhere NW swell in excess of 8 ft will more or less
dominate the waters west of 110W through Sun. Very large NW
swell, in excess of 20 ft, will enter NW portions of the
forecast area early Sun in conjunction with the arrival of a
strong cold front. Seas of 12 ft or above could encompass almost
all of the forecast waters N of 07N and W of 115W by Tue morning.