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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 270831

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Wed Sep 27 2023

Tropical Weather Discussion for the eastern Pacific Ocean from
03.4S to 30N, east of 120W including the Gulf of California, and
from the Equator to 30N, between 120W and 140W. The following
information is based on satellite imagery, weather observations,
radar, and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0830 UTC.


A tropical wave is along 85W north of 06N, moving west at 5 to 
10 kt. No significant convection is noted near the tropical wave 
axis at this time. 

A tropical wave is analyzed along 126W from 04N to 17N, moving W
at 10 to 15 kt. Scattered moderate convection is active from 10N
to 13N between 125W and 127W. A recent scatterometer satellite
pass shows a well defined trough at the surface along 126W, with
moderate to fresh easterly winds farther north between the trough
and the subtropical ridge to the north. 


The monsoon trough extends from 09N83W to 09N115W. Segments of 
the ITCZ extend from 09N115W to 08N123W, and from 06N127W to 
09N140W. Scattered moderate convection is noted within 90 nm
south of the ITCZ west of 135W.


A recent scatterometer satellite pass indicated moderate to fresh
NW winds persisting off Baja California, between high pressure 
to the northwest and a trough to the east. Wave heights will 
build off Baja California due to the arrival of long-period NW 
swell. A recent altimeter pass along with a couple of the ship 
observations showed combined seas are already 10 to 12 ft mainly 
off Baja California Norte. Gentle to moderate breezes farther 
south and in the Gulf of California, with 4 to 6 ft seas in open 
waters with mixed swell. 

For the forecast, the moderate to fresh NW winds will persist 
off Baja California north of Cabo San Lazaro through the morning 
between high pressure north of the area and a trough over the 
Gulf of California. Winds will then gradually diminish through 
Fri as the ridge shifts NW. Seas of 8 to 12 ft in NW swell will 
persist through Thu offshore Baja California before slowly 
subsiding Fri through Sat. Farther south, moderate to fresh N gap
winds will pulse to strong across the Gulf of Tehuantepec 
tonight. Looking ahead, expect fresh westerly gap winds over the 
northern Gulf of California will start Fri afternoon, ahead of an
approaching cold front, possibly reaching near-gale force by Sat


Light and variable breezes are evident off northern Central 
America, north of the monsoon trough. Gentle S to SW breezes are
noted farther south, except moderate winds S of 04N. Combined 
seas are 4 to 5 ft across the region with southerly swell.

For the forecast, gentle to moderate winds will prevail to the north
of 05N with seas 5 ft or less through Sun night, with moderate SW
winds farther south. Seas south of 05N will build to 6 to 9 ft 
in southerly swell through Fri evening, with seas highest to the 
SW of the Galapagos. 


The remnant trough that was T.C. Fourteen-E is passing west of
the area. A recent scatterometer satellite data indicated mostly
fresh winds are still accompanying the low within 180 nm in the 
northern semicircle, implying a large area of rough seas of 9 ft
there. Farther north, altimeter satellites passes continue to 
indicate of long- period NW swell crossing 30N and moving into 
the discussion waters. To the south, satellite altimeter data 
also showed seas to 8 ft crossing the equator between 110W and 
120W. This is part of a large area of southwest cross-equatorial 
southerly swell moving into the waters south of 03N and west of 

For the forecast, high pressure north of the front will increase
the pressure gradient to the west of 125W, and freshen the winds
through Thu. Large, long-period NW to N swell will continue to 
propagate into the waters north of 22N, then cover the area north
of a line from Baja California Sur to 10N120W to 10N130N by late
today. Meanwhile high pressure will build north of the area, 
supporting fresh to strong trade winds by Wed from 10N to 20N 
west of 120W, with combined seas building to 13 ft in a mix of 
NW swell and shorter period NE to E wind waves. Farther south, 
southerly swell will continue to move across the equator, 
supporting combined seas of 8 to 9 ft south of 03N and west of 
115W by Thu.