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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 260907

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Tue Sep 26 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
0900 UTC.


A tropical wave is entering the eastern Pacific, passing through
western Panama north of 05N. Scattered moderate convection is
active from 05N to 06N between 84W and 85W. 

A tropical wave is analyzed along 121W from 04N to 17N, moving W
at 10 to 15 kt. Scattered moderate convection is active from 12N
to 13N between 121W and 122W.


The monsoon trough extends from 08N85W to 10N125W. The ITCZ 
extends from 09N135W to beyond 09N140W. Scattered moderate 
convection is evident from 06N to 08N between 97W and 99W.
Scattered moderate to isolated strong convection is noted from
07N to 09N between 108W and 110W.


A surface ridge extends from 1024 mb high pressure centered near
30N125W to Baja California Sur. Various ship observations from 
the past evening showed fresh NW winds off Baja California, and 
combined seas there are likely 5 to 7 ft. The pattern is also 
supporting moderate to fresh NW winds over the central Gulf of 
California as noted in a recent scatterometer satellite pass, 
with lighter winds elsewhere. Gentle breezes are noted farther 
south, with 3 to 5 ft seas. 

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


Light and variable breezes are evident off northern Central 
America, north of the monsoon trough, with gentle SW breezes
noted farther south. Combined seas are 3 to 5 ft across the
region with a component of southerly swell. Scattered showers and
thunderstorms are evident beyond 90 nm offshore of Nicaragua and
El Salvador. A few showers and thunderstorms are starting to
develop closer to shore in the Gulf of Papagayo and off southern

For the forecast, gentle to moderate winds prevail to the north 
of 07N with seas 5 ft or less through Sat night. Gentle SW winds 
farther south will increase to moderate mainly south of 05N 
starting late Tue, with combined seas building to 6 to 8 ft in 
southerly swell off Ecuador. 


The remnant low of T.C. Fourteen-E is fully exposed near 15N132W
with a pressure estimated to be 1010 mb. A recent scatterometer 
satellite pass indicated mostly fresh winds are still 
accompanying the low within 90 nm in the northern semicircle, 
implying rough seas near the low pressure as well. Farther north,
and altimeter satellite pass from 0330 UTC showed seas to 9 ft 
near 30N140W. This is indicative of long- period NW swell 
reaching the discussion waters accompanying a cold front moving 
through the north- central Pacific. Altimeter data also resolved 
combined seas to 7 ft farther south, part of a large area of 
southwest cross- equatorial southerly swell moving into the 
waters south of 03N and west of 100W. 

For the forecast, the remnants of T.C. Fourteen-E will weaken to
a trough during the next 48 hours while moving west-southwestward.
The cold front approaching 30N140W will stall and dissipate north
of 28N and west of 135W into mid week. High pressure north of 
the front will increase the pressure gradient to the west of 
125W, and freshen the winds Tue through Thu. Large, long-period 
NW to N swell will propagate into the waters north of 22N by this
evening, then cover the area north of a line from Baja 
California Sur to 10N120W to 10N130N by late Wed. Meanwhile high
pressure will build north of the area in the wake of the front,
supporting fresh to strong trade winds by Thu 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 late Thu.