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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 201558
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Mon Nov 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 
1430 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: Gale force 30 to 40 kt 
northerly winds will continue until midday today, with maximum 
seas of 17 ft downstream of the gulf waters near 13.5N96W at 
sunrise earlier today, and forecast to subside during the next 
24 hours. The wind speeds will diminish gradually during the 
next 24 hours, and to 20 knots or less just after sunrise on 
Tuesday. The associated NE swell will propagate SW mixing with 
long-period cross-equatorial swell, resulting in an area of 8 ft 
and greater seas of across the waters from roughly 09N to 14N 
between 94W and 103W on Mon in the early evening. Two areas of 8 
foot sea heights will remain just after sunrise on Tuesday... 
one from 14N to 15.5N between 94.5W and 95.5W, and the other one 
from 08N to 11N between 102W and 105W. The areas of 8 foot sea 
heights are forecast to disappear completely late in the 
afternoon on Tuesday. Strong N winds are expected to resume on 
Wed afternoon, with gale conditions from Wed evening until 
midday on Friday, with maximum sea heights of 18 feet near 
13.5N95.5W on Thursday morning.   

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough passes through Panama near 08N81W, to 06N90W, 
to 07N106W. The ITCZ continues from 07N106W to 10N120W to 
10N140W. Precipitation: scattered moderate to strong within 120 
nm to the S of the ITCZ between 131W and 135W, and within 120 nm 
to 240 nm to the N of the ITCZ between 138W and 140W. Scattered 
moderate to isolated strong within 180 nm to the N of the ITCZ 
between 121W and 130W, and within 150 nm to the S of the ITCZ 
between 127W and 129W. Widely scattered moderate to isolated 
strong from 02N to 07N from 80W eastward.

A dissipating cold front is just to the west of the area. 
Precipitation: widely scattered moderate to isolated strong from 
22N northward from 135W westward.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please read the Special Features paragraph for the GALE 
WARNING in the Gulf of Tehuantepec. 

A NW to SE orientated ridge just beyond 250 nm seaward will 
maintain moderate NW flow W of the Baja Peninsula through mid 
morning when the pressure gradient will relax, supporting light 
northerly winds through late wed when a trough will form SW from 
the central Baja Peninsula to near 22N116W and continue through 
early Fri before filling. Expect seas in the 3 to 5 ft range 
through Thu building to 5 to 7 ft N of 25N late in the week.  

Gulf of California: The earlier moderate NW flow has been 
diminishing this morning. This situation will continue, until 
reaching light breezes from later today until Tue morning. 
Moderate to locally fresh conditions will develop,again, on 
Tuesday morning, and continue until early Wed. Light to moderate 
NW flow is expected on Thu and Fri, becoming light and variable 
on Fri night.   

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

Gulf of Papagayo: Moderate to locally fresh NE drainage winds 
are forecast during the overnight hours tonight, then light 
drainage flow expected during the overnight hours through Thu 
night, with fresh to locally strong nocturnal drainage possible 
on Fri and Sat nights.

Light and variable winds, and 3 to 5 ft seas, are expected 
elsewhere to the N of the monsoon trough which has been 
meandering from 09N to 11N, while moderate to locally fresh 
southerly winds, and 4 to 7 ft seas, are forecast S of the 
monsoon trough this week.  

REMAINDER OF THE AREA...

A NE to SW aligned ridge will meander from 32N125W to beyond 
20N140W for the next several days. Strong to occasionally near 
gale force southerly winds, that are currently across the waters 
N of 28N W of 138W, will spread E across the waters generally W 
of a line from 32N130W to 22N140W through late tonight before 
the pressure gradient relaxes. Associated seas are expected to 
build to 8 to 12 ft across the waters S of 30N, while 10 to 14 
ft seas are forecast from 30N to 32N. A series of cold fronts 
will approach, but stall just W of 140W through Tue night. Model 
guidance is suggesting a cold front will arrive at 32N140W on 
Wed, and stall from 32N136W to 23N140W on Thu, with seas 
building 12 to 17 ft W of the front through Thu. 

Moderate anticyclonic flow expected across the tropics N of the 
ITCZ and W of 120W through the middle of next week, with seas of 
4 to 7 ft. Long period NW swell will propagate E across the 
discussion waters W of 120W from mid to late week, and subside 
during the upcoming weekend.

$$
mt