AXPZ20 KNHC 130340
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 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 0000 UTC surface analysis and satellite imagery through
...Gulf of Tehuantepec Gale Warning...
Winds continue to diminish this evening across the Gulf as high
pressure over the Gulf of Mexico weakens and shifts east. Light
to gentle winds are expected tonight through Thu night. Seas of
8 to 9 ft within 250 nm of the coast of Oaxaca and Chiapas will
subside below 8 ft through tonight as well. The improved marine
conditions will be short-lived, however, as a cold front
forecast to move into the Gulf of Mexico on Thu is expected to
initiate another strong gale force wind event late Fri through
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 09.5N72W TO 09.5N83W TO 05N100W.
The ITCZ extends from 05N100W TO 09N117W TO 10N130W to beyond
08N140W. No significant convection is observed.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
Over open waters off the Baja California coast, lingering long
period NW swell along the length of the coast and in the
Revillagigedo Islands will decay below 8 ft through tonight,
just ahead of another pulse of NW swell, expected to reach the
northern section of Baja California Norte and Guadalupe Island
by Thu night. This new swell will reclaim the territory vacated
by the previous swell through early Sat with significant wave
heights reaching 10 ft.
Strong high pressure building over the Great Basin will support
a push of fresh to strong winds into the northern Gulf of by
early Thu, eventually spreading across most of the Gulf through
Fri with seas approaching 8 ft over the southern Gulf where the
fetch would be longest. Winds and seas will subside through Sat
as the high pressure shifts eastward into the Central Plains.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
Gulf of Papagayo...Overnight gap winds have been active for the
past several nights, but will only reach 20 kt tonight and Fri
night as high pressure north of the area shifts eastward. Fresh
to strong gap winds with seas to 9 ft will resume during
overnight and early morning hours Sat night as the next system
builds north of the region.
Gulf of Panama...Fresh northerly winds will pulse to around 20
kt overnight and build downstream seas to 5-7 ft through Thu
morning before winds back to the NW and 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 in the 4-6 ft range.
REMAINDER OF THE AREA...
A large area of confused seas persists over much of the north
Pacific east of 110W, consisting of primarily NE and E swell
mixed from gap winds, merging with longer period NW swell.
Combined sea heights in this area are still reaching up to 11
ft, but will be subsiding below 8 ft through Thu night.
Farther west, a surface trough continues from 08N132W TO
13N128W. The pressure gradient between this trough and 1029 mb
high pressure north of the region centered along the subtropical
ridge near 32N139W is supporting generally fresh trade winds
from the ITCZ to 20N, west of 115W. Scatterometer passes from 18
UTC indicated fresh to strong NE winds within 180 nm west of the
trough. Seas are 8 to 12 ft in this area, in a mix of local seas
from the trade winds and longer period NW swell. The high
pressure will weaken through Thu ahead of a cold front
approaching from the west, allowing the trade winds to diminish.
The next 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 as it moves east to the north of
20N, 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. Looking ahead, a more substantial group of NW
well will move into the area by early Sun.