AXPZ20 KNHC 122205
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2204 UTC Wed Dec 12 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
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 06N77W to 05.5N95W. A segment of
the intertropical convergence zone continues from 05.5N95W to
08N125W, and again from 08N135W to beyond 08N140W. No
significant convection is observed.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
Gulf of Tehuantepec...Winds continue to diminish this afternoon
and evening 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. he reprieve will be short 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
Farther north, 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.
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 group of NW swell reaching 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.
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 east. 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...Northerly swell from early gap winds will
persist into the evening then subside.
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 with a component of 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 persists form 07N130W to 15N125W.
The gradient between this trough and 1032 mb high pressure north
of the region centered along the subtropical ridge near 32N140W
is supporting generally fresh trade winds from the ITCZ to 20N,
west of 115W. Scatterometer passes from 18 UTC indicated this,
as well as 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 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.