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 Eastern Pacific Basin Tropical Discussion Atlantic | East Pacific 
AXPZ20 KNHC 120220

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0300 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  0 UTC surface analysis and satellite imagery through
0300 UTC.


An earlier scatterometer pass confirmed gap winds to gale force
through the Gulf of Tehuantepec, following a cold front that
moved across southern Mexico early this morning. These gale 
force winds may be peaking around 45 kt currently, with seas 
peaking around 17 ft overnight. Gale force winds will gradually 
diminish through Thu, before tapering off to strong then fresh 
Thu night through Fri. Gap winds will be below 20 kt by Sat 


The monsoon trough extends from 07N78W to 10N110W to 1010 mb low
pressure near 08N120W. The intertropical convergence zone 
continues to beyond 08N140W. Satellite derived data of lightning 
shows scattered moderate thunderstorms from 10N to 13N between 
105W and 108W. 


1026 mb high pressure centered near 29N130W is maintaining 
moderate northerly flow off the coast of Baja California, 
depicted well in recent scatterometer data and ship observations.
The scatterometer data also showed fresh to strong NW winds 
across the Gulf of California between 25N and 28N between the 
high pressure to the west and resident troughing over northwest 
Mexico. Concurrent altimeter satellite passes indicated 4 to 6 ft
seas off the coast of Baja California and 3 to 5 ft seas in the 
central and southern Gulf of California. 

The high pressure will persist west of the area through Fri,
supporting moderate to occasionally fresh NW winds off Baja
California. A new round of long period NW swell in excess of 8 ft will
reach the waters around Guadalupe Island and the northern coast 
of Baja California Norte by Thu night, reaching the Revillagigedo
Islands by late Sat. Looking ahead, a trough or weak front will
move into the waters off northern Baja California Norte by late
Fri into Sat, supporting fresh to strong NW winds in that area,
but allowing winds to diminish over the Gulf of California. Seas
may reach 13 ft in NW swell over 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 northerly flow over 
the Gulf of California early next week.

Farther south, gentle to moderate winds and 3 to 5 ft seas will 
persist off the southern Mexico coast between Tehuantepec and 
Cabo Corrientes into Fri, increasing slightly mainly off the 
area around Cabo Corrientes late Fri and Sat as the pressure 
gradient tightens. 


Fresh to strong NE to E winds will pulse over the Gulf of 
Papagayo tonight with seas peaking near 8 ft, 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 flow 
prevails across the Gulf of Panama.


A 1026 mb high pressure center located near 29N130W is supporting
fresh to strong tradewinds across the waters south of 25N and 
west of 115W. Recent altimeter data showed seas of 8 to 10 ft in 
the area of fresh trades. The high will move slightly southwest 
through Thu night and act to increase the pressure gradient to 
its south, and expand the area of strong tradewinds to south of 
26N and west of 120W.

A cold front will approach 30N140W and stall Thu. Large NW swell
generated by gales behind the front are running ahead of front.
Seas will build across the region, particularly where the longer
period NW swell mixes with the shorter period easterly trade wind
swell. Seas will eventually peak between 12 and 14 ft Thu night 
and Fri morning in this area. A surface trough or weak low
pressure area heading west along will further tighten the 
pressure gradient just north of the ITCZ west of 130W Fri night 
and Sat.


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