AXPZ20 KNHC 092205
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2151 UTC Sun Dec 9 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: High pressure is pressing
southward along the eastern slopes of the Sierra Madre Oriental
mountains of Mexico. The large pressure difference between the
high and lower pressure south of Mexico will result in an abrupt
onset of strong to near gale force north to northeast winds,
which will surge southward across the Isthmus of Tehuantepec and
out over the Gulf of Tehuantepec. Strong winds have already begun
to affect the Gulf N of 14N. These winds will quickly increase
to strong gale force this evening. Seas in the gale area are
forecast to build to between 12 and 18 ft by late tonight. The
strong gale force winds will continue through Tue, then diminish
to minimal gale force Tue night. Winds will then quickly decrease
and become light by Wed evening as the strong high over the Gulf
weakens and shifts eastward. Swell from this event is forecast
to propagate S and SW well away from the Gulf of Tehuantepec
region, with the leading edge of the 8 ft seas expected to reach
near 09N110W by late Tue night or Wed. Please refer to the
Eastern Pacific High Seas Forecast under AWIPS/WMO headers
HSFEP2/FZPN03 KNHC for more specific marine details.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough axis extends from low pres 1010 mb near
06N74W to 05N83W to 05N90W. The ITCZ continues from 05N90W to
07N104W, then resumes from 10N113W to 09N123W to beyond 07N140W.
Scattered moderate and isolated strong convection is noted within
90 nm either side of a line from 05N118W to 08N131W. A surface
trough splits the ITCZ from 06N109W to 10N109W to
14N109W. Scattered moderate and isolated strong convection is
seen from 11N to 14N between 105W and 110W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
A 1027 mb high pressure area is centered west of northern Baja
California Norte near 32N124W. Strong high pressure is currently
centered over the Great Basin as well. The pressure gradient
between these high pressure areas and enhanced troughing across
the Gulf of California is supporting fresh to strong NW winds
across mainly southern half of the Gulf of California. Seas in
this area are estimated to be as high as 5 ft. Looking ahead,
strong high pressure building over the Great Basin well north of
the area will support strong NW winds over mainly the northern
Gulf of California Thu.
Recent satellite-derived sea height data show most of the large,
long- period NW swell inundating the open waters over the past
couple of days have subsided below 8 ft, with the exception of
the area near the Revillagigedo Islands. A new group of NW swell
in excess of 8 ft will reach the waters off the northern Baja
California coast and near Guadalupe Island by late Mon, then
spread east to cover most of the waters off the entire Baja
California peninsula and the Revillagigedo Islands through Tue
night, before subsiding below 8 ft through Wed.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
Gulf of Papagayo...Winds will pulse to strong intensity during
the overnight and early morning hours over the Gulf of Papagayo
beginning tonight and through Wed night as high pressure shifting
eastward over the Gulf of Mexico builds southward toward the NW
Caribbean Sea and Central America.
Elsewhere, gentle to moderate winds will persist on either side
of a weakening monsoon trough and seas in the range of 4 to 6 ft.
REMAINDER OF THE AREA...
A cold front extends from near 32N133W to 27N140W. Long-period
NW swell is following in behind this front, and will bring seas
in excess of 8 ft over most of the area west of 120W through
early Tue. This will reinforce older, decaying NW swell
lingering south of 20N, mixed with shorter period trade wind
swell. High pressure building behind the front will support
generally fresh trade winds over the deep tropics west of 125W
through mid week, with fresh to strong winds possible west of
135W. Trade wind convergence along with an assist from divergent
flow aloft on the southeast side of a broad upper trough over
Hawaii is supporting clusters of showers and thunderstorms along
the ITCZ, and this will persist sporadically through early in the
Wave model guidance suggests that a rather large area of 8 ft
seas associated with mixed swell will exist Wed morning from
about 03N to 13N between 94W and 110W as a result of long period
northwest swell mixing with shorter period northeast swell that
propagate downstream from the Gulf of Tehuantepec and to a
smaller extent those induced by the Gulf of Papagayo strong
pulsing northeast winds.