000
AXPZ20 KNHC 201518
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1518 UTC Wed Dec 20 2017

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 1200 UTC surface analysis and satellite imagery through
1400 UTC.

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

The monsoon trough extends from 1010 mb low pres near 06N78W to
07N95W, where the ITCZ begins and extends to 09N120W to 10N140W.
Widely scattered moderate convection is within 90 nm of either
side of the ITCZ axis W of 108W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Gulf of California: Northerly winds will increase abruptly to 
fresh or strong behind the next cold front expected to move 
through most of the basin early Thursday through Friday. Winds 
should drop back to fresh breeze by Saturday. These strong winds 
are also forecast to seep through Baja California mountain 
passages and into the open Pacific waters west of the peninsula 
on Friday, but only peaking near 20 kt. Seas over the N gulf 
will peak near 8 ft during the strong winds. Seas west of the 
Baja California Norte will reach 8 to 9 ft in combined wind 
driven waves and NW swell. 

Gulf of Tehuantepec: Northerly winds pulsing fresh to strong 
through this morning will pulse again Wednesday night before 
diminishing. Looking ahead - gale force winds will be possible 
over the gulf Sunday night as a strong cold front moves across 
the Gulf of Mexico, and winds funnel through the Chivela pass 
into the Gulf of Tehuantepec beginning late Saturday night.
Strong winds Saturday night and Sunday will increase to gale 
force Sunday night through Tuesday morning. The peak magnitude of
the event is likely to be early Monday. Peak seas may reach 20 
ft Monday.

Elsewhere across the offshore waters of Mexico, mainly gentle to
moderate winds are expected the next several days, with the
exception of briefly fresh winds from Manzanillo to Cabo San
Lucas as high pressure builds NW of the region Friday and 
Saturday. Seas of 4 to 6 ft will persist the next several days,
except near 7 ft where the fresh winds are occurring. 

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

Fresh to strong winds will prevail through Thursday before 
diminishing on Friday with seas reaching near 7 ft through
Thursday. Gentle to moderate winds and seas of 5 to 7 ft will 
persist elsewhere over these waters through the upcoming 
weekend.  

REMAINDER OF THE AREA...

Moderate to fresh east to northeast winds prevail over the waters
from the ITCZ to 30N, driven by high pressure centered north of
the region. These winds support 6 to 8 ft seas in a NW swell. To
the south of the ITCZ, moderate SE winds prevail with seas of 5
to 7 ft. An upper trough with an axis from 24N127W to 11N111W
supports numerous moderate and isolated strong convection from 
12N to 20N between 107W and 115W. 

High pressure will build SE toward California on Friday
while low pressure develops west of our waters near roughly
22N147W. The pressure gradient between these two features
will support fresh to strong SE winds north of 18N and west of
135W Friday through Saturday night. Winds will diminish from 
south to north as the low lifts northeast during this time, with
forecast models suggesting the low center will clip our waters 
near 30N140W Saturday night. Seas of 8 to 15 ft are expected 
during this time period over these affected waters. Later in the
forecast period, a weaker pressure pattern will result in mainly
moderate winds over the area. However, lingering swell of 8 to 
12 ft will remain over the NW waters N of 20N and west of 133W 
through early next week. 

$$
Latto