000
AXPZ20 KNHC 162216
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Fri Dec 16 2016

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
2130 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec...The Gale Warning in effect for the Gulf of
Tehuantepec have been discontinued. An overnight ASCAT pass
indicated only 20 to 30 kt, which likely increase to minimal
gale force this morning, and seas 8 to 11 ft. Regional coastal
observations suggest that winds are diminishing asforecast by
the global models, and are likely down to 20-25 kt this
afternoon, and should reach around 20 kt only across the
immediate Gulf of Tehuantepec this evening, and then less than
15 kt by Saturday morning. The Gale Warning has thus been
discontinued. A stronger cold front over the weekend could
produce a more significant northerly gale wind event beginning
on Monday. Currently, marine guidance suggests northerly winds
of 35-45 kt and building seas of 14-16 ft by Monday evening with
this next gale force gap wind event.

Gulf of California...A cold front approaching the region from
the west is forecast to reach Baja California Norte this evening
and move eastward across the region, including the northern part
of the Gulf of California by tonight. Expect strong westerly
winds north of 29N over the far northern Gulf by this evening
ahead of the front, then veering to the northwest and briefly
increasing to minimal gale force tonight into the early morning
hours of Saturday as the front moves east of the area. Strong
northwest to north winds will then spread southward across the
Gulf of California Sat and Sat night as the front moves
southeastward into central Mexico.
  
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...  

The monsoon trough extends from 1010 mb low pressure near
06N78.5W to 08N87W to 07N99W. The ITCZ continues from 07N99W to
1012 mb low pressure near 10N108.5W to 08N119W to 09N133W to
beyond 08N140W. Scattered moderate isolated strong convection is
from 04N to 07.5N E of 80W. Similar convection is from 09N to
15N between 105W and 110W, and from 08N to 10N between 125W and
130W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A Gale warnings is in effect for the Gulf of California. See
Special Features section above for details.

High pressure west of Baja California that past few days has
continued to slowly weaken and drift southeastward, ahead of an
approaching cold front that is nearing 30N120W. Gentle to
moderate northerly winds of the past 2 days have backed to the
west and northwest this afternoon and will gradually increase to
around 15 kt this evening. The cold front is expected to move
across the N waters from west to east this evening through
Saturday, and will bring fresh to strong NW flow to the waters
off of Baja California Norte behind the front by early Saturday,
with seas building to 8 to 10 ft behind the front. Fresh NW
winds and 5 to 8 ft seas will spread south across the waters off
of Baja California Sur. These winds and seas will diminish late
Saturday through Sunday as high pressure builds eastward behind
the front. Elsewhere offshore of Mexico, and outside of the Gulf
of Tehuantepec and Gulf of California, gentle to moderate
breezes and 3 to 5 ft seas will persist.
     
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Fresh to strong northeast winds are expected across the Gulf of
Papagayo during the overnight and early morning hours through
Monday, with the assistance of the nocturnal drainage flow. Seas
should build 6-8 ft during the peak of each nights wind. A
larger gap wind event appears to be in store for most of zone
PMZ113 and southern portions of PMZ111 off El Salvador and
Guatemala Monday night into Tuesday morning, as strong trade
wind flow in the southwest Caribbean funnels across Central
America. Marine guidance indicates fresh to strong winds across
the Gulf of Fonseca and the Gulf of Papagayo extending westward
to beyond 92W/93W by Tuesday morning, with seas building up to
10-11 ft W of 90W. Moderate northerly winds are expected across
the Gulf of Panama at that time.

REMAINDER OF THE AREA...

A cold front extends from 30N121.5W to 28N127W then become a
weakening front to 24.5N140W, and will continue to move east
across the N waters through Saturday. This will keep the
subtropical ridge fairly weak, with moderate to locally fresh
trade wind flow in the deep tropics.

However, the trade winds will increase across the west-central
waters this upcoming weekend as strong high pressure builds
north of the area behind the front. Trade winds in the 20 to 25
kt range are anticipated from 10N to 18N W OF 130W Saturday
morning, and from 08N to 13N W OF 135W, and from 13N to 18N W OF
130W Sunday morning. Fresh to strong NE-E winds are forecast to
blow across most of the waters N of 07N W of 130W and N of 16N W
of 123W by Sunday night. These marine conditions are expected to
persist on Monday, with winds likely increasing to 30 kt and
seas building to 11-12 ft across the west-central waters.

A weak 1012 mb surface low is centered along the monsoon trough
near 10N108.5W, with a surface trough extending north to
15N109W. Fresh easterly winds were noted early this morning per
scatterometer data within about 150 nm NE quadrant of the low
center. The surface low will gradually dissipate through
Saturday as it drifts west across the tropics. Although the
surface low will dissipate, then accompanying broad low level
cyclonic circulation, and surface trough will persist a couple
of more days, and reach near 120W by Sunday night. While winds
and seas in the vicinity of this feature are not strong, very
active weather continues with the wave like feature and is
expected to shift westward with it through at least Saturday.
  
$$
Stripling