000
AXPZ20 KNHC 122159
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2158 UTC Thu Dec 12 2019

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
meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends from 10N85W to 07N98W. The
intertropical convergence zone continues from 07N98W to 1009 mb
low pressure near 10N123W, then on to beyond 06N140W. Satellite
derived lightning data shows thunderstorms from 10N to 12N
between 94W and 96W, from 13N to 15N between 105W and 110W, and
from 07N to 10N between 121W and 124W. 

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

In the Gulf of Tehuantepec, gap winds to near gale force persist
this afternoon, diminishing from strong gales last night. The
winds will continue to diminish as high pressure north of the
area shifts eastward. Seas ranging from 8 to 13 ft extend up to
500 nm downstream of the Gulf of Tehuantepec. Winds and seas will
continue to subside through Fri as the pressure gradient relaxes
over the region. 

1026 mb high pressure centered near 31N132W is maintaining 
moderate northerly flow off the coast of Baja California.
Moderate to fresh NW winds persist across the Gulf of California
between the high pressure to the west and resident troughing 
over northwest Mexico. Recent altimeter and ship observations
indicate seas of 8 to 10 ft just west of Guadalupe Island. This
is long period NW swell moving into the area. Elsewhere off Baja
California, the altimeter data also suggest seas hovering 
between 4 and 6 ft seas, and 3 to 5 ft seas in the central and 
southern Gulf of California. 

The high pressure will support moderate to occasionally fresh NW
winds off Baja California through Fri. The long period NW swell 
in excess of 8 ft will continue through the offshore waters of
Baja California and reach the Revillagigedo Islands by late Sat.
Looking ahead, a trough or weak front moving into the waters off
northern Baja California Norte late Fri or Sat will generate 
fresh to strong NW winds in that area, but cause winds to 
diminish over the Gulf of California. Seas may reach 13 ft in NW 
swell in the open waters off Baja California. The front or trough
will weaken as it moves southward through Sun, but high pressure
in the wake of this boundary will support another round of fresh
to possibly strong N flow over the Gulf of California Mon and 
Tue.

Farther south, gentle to moderate winds and 3 to 5 ft seas will 
persist off the southern Mexico coast between Tehuantepec and 
Cabo Corrientes through Fri, then increase in the vicinity of 
Cabo Corrientes late Fri and Sat as the pressure gradient 
tightens. Large N to NE wind swell will propagate S and away from
Tehuantepec through tonight, even as winds diminish there. This 
will keep offshore seas at 6 to 9 ft across the far offshore 
waters south of Acapulco to Puerto Angel through Fri morning. 

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND 
WITHIN 750 NM OF ECUADOR... 

Fresh NE to E winds will pulse to strong over the Gulf of 
Papagayo through Fri, then moderate to fresh winds are expected 
for the remainder of the forecast period. Elsewhere, gentle to 
moderate S to SW monsoon flow will persist across the offshore 
waters of Costa Rica, Panama, Colombia, and Ecuador through Sat 
night, while moderate NW to N flow prevails across the Gulf of 
Panama. 

REMAINDER OF THE AREA...

A fairly tight pressure gradient between a 1026 mb high pressure
center located near 31N132W and 1009 mb low pressure centered
along the ITCZ near 10N123W is supporting fresh to strong trade 
winds across the waters south of 25N and west of 120W. In fact, a
recent scatterometer satellite pass showed winds near 30 kt
within 120 nm in the north semicircle of the low pressure.
Concurrent altimeter data showed seas of 8 to 11 ft in the area 
of fresh trades. The low pressure will weaken gradually as it
continues to shift westward along the ITCZ over the next couple
of days. Meanwhile the high pressure will shift slightly 
southwest through Thu night.

Large NW swell generated earlier by gale force winds behind a
front stalled near 30N140W are spreading out to the southeast of
the front. Seas will build north of the ITCZ and west of 120W, 
particularly where the longer period NW swell mixes with the 
shorter period NE to E trade wind swell. Seas will eventually 
peak between 12 and 14 ft tonight and Fri morning in this area. 
Westward moving areas of low pres will act to increase the 
pressure gradient south of the high and expand the area of 
strong trade winds to south of 25N and west of 120W.

$$
Christensen