000
AXPZ20 KNHC 182121 RRA
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Tue Dec 18 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
meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through 
2115 UTC.

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

The ITCZ extends from 06N93W to 07N120W to 07N140W. Scattered 
moderate convection is noted from 04N to 11N between 108W and 
120W, and from 08N to 19N between 118W and 131W. Isolated 
moderate convection is from 04N to 07N between 99W and 104W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Gulf of Tehuantepec: Moderate to fresh winds are over the Gulf 
of Tehuantepec with seas reaching 9 ft. Seas will subside below 
advisory criteria this evening. The next gale event is expected 
to start by Thu evening as a cold front pushes across the Gulf 
of Mexico north of the area. Strong gales with seas reaching as 
high as 18 ft will persist through late Fri and early Sat. Fresh 
to strong winds will then prevail through the remaining weekend 
as high pressure builds along Mexico tightening the gradient in 
Tehuantepec.

Large NW swell is impacting the forecast waters, with the 
leading edge of 12 ft seas or greater noted in the waters off 
Baja California Peninsula. This swell will produce hazardous 
seas for mariners, and create large and powerful surf along the 
Pacific reefs and beaches. This high surf will also produce 
coastal flooding and beach erosion in many exposed locations 
from southern California to western Mexico. This swell will 
decay to 8 to 11 ft by late Wed, just ahead of another round of 
NW swell to 12 ft reaching Guadalupe Island and the northern 
coast of Baja California early on Thu. This swell will also 
decay below 12 ft rapidly, leaving 8 to 10 ft NW swell in place 
for the Mexican open waters west of 105W through Sat.

Across the Gulf of California, strong high pressure will build 
over the Great Basin by Wed. The high will support fresh to 
strong winds across the northern and central Gulf Wed through 
Thu morning, while seas build to 5-8 ft.

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

Fresh to strong gap winds will prevail across the Gulf of 
Papagayo and other typical gap wind zones of Central America 
through tonight. A strong cold front will move across the SW 
Atlc and the SW Caribbean on Thu, supporting gap winds in the 
Gulf of Papagayo beginning early in the afternoon Fri. Winds are 
expected to increase to near gale force late Fri with seas 
building to 11 ft Sat morning. Winds and seas will start to 
diminish by Sun night. 

Farther south, fresh to strong trade winds across the southwest 
Caribbean will support fresh gap winds over the Gulf of Panama 
through tonight. 

Elsewhere, gentle to moderate winds will persist, with seas 
in the 4 to 6 ft range.

REMAINDER OF THE AREA... 

High pressure of 1029 mb is centered N of the area near 31N128W.
This high will meander about this area for the next few days and
maintain a modest pressure gradient to the south and southwest, 
resulting in moderate to fresh tradewinds between 10N and 20N to 
the W of 110W. Large NW swell moving through the area is 
producing seas of 10-17 ft. Seas associated to this swell have 
start to slowly subside. Another set of NW swell will move into 
the far NW waters Wed, with seas peaking near 16 ft over this 
area early Wed. The NW swells will maintain seas of 8 ft or 
greater over much of the open waters W of 100W through early 
this weekend. A surface trough will approach the western 
tropical waters on Fri night, increasing the winds to fresh to 
strong for the region 08N-15N west of 133W. 

$$
NR