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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 252157

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Mon Sep 25 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 1800 UTC surface analysis and satellite imagery through
2040 UTC.


A tropical wave is analyzed along 118W from 04N to 17N, moving W
at 10 to 15 kt. Scattered moderate to strong convection is from 
04.5N to 13N between 113W and 124W.


The monsoon trough extends from 10.5N74.5W to 08.5N91W to
10.5N104W to 09.5N116W. The ITCZ extends from 11N129W to 09.5N140W.
Scattered moderate to strong convection is noted from 03.5N to 
08N E of 84W, from 04.5N to 10N between 86W and 111W, and from
09N to 12N between 126W and 130W. Scattered moderate isolated 
strong convection is noted about the tropical wave from 04.5N to 
13N between 113W and 124W.


A modest surface ridge continues to dominate the offshore 
forecast waters of Baja California, centered on a 1021 mb high 
near 30N124W. This pressure pattern is supporting mainly fresh 
NW-N winds from near Cabo San Lazaro northward. Seas are 5-7 ft 
in NW swell offshore Baja California. Inside the Gulf of
California, N-NW winds have increased to fresh across central 
portions between 26N and 28N, where seas have built to 4 ft. 
Winds are moderate or weaker elsewhere, with seas of 4-5 ft, 
except 1-2 ft in the northern Gulf of California. Scattered 
moderate to strong convection persisting across the coastal 
waters of southwestern Mexico continues from 13N to 16N between  
98W and 102W.

For the forecast, the surface ridge across the offshore waters 
will persist through Wed before high pressure reorganizes well 
NW of the region. Moderate to fresh NW-N winds offshore Baja 
California from near Cabo San Lazaro northward will increase to 
fresh to strong this evening and continue through early Wed. 
Winds will then gradually diminish Wed through Fri as the ridge 
shifts NW. Moderate N winds will pulse to strong across the Gulf 
of Tehuantepec each of the next few nights. Seas will build 8 to 
12 ft in new NW swell offshore Baja California Tue through Thu 
before slowly diminishing Fri through Sat.

Looking ahead, low pressure is expected to develop across the 
northern Gulf of California by Thu, and induce strong SW winds 
across a large portion of the northern Gulf Fri night. 


Winds are generally gentle to the north of 07N, where seas are 
4-5 ft. Moderate S to SW monsoonal winds prevail elsewhere to 
the south of 07N, from offshore Ecuador to the Galapagos Islands.
Seas there are 5 to 6 ft. Scattered thunderstorms have flared up
this afternoon to the north of 03.5N and east of 84W, as a
tropical wave is moving across Panama and the local waters.

For the forecast, Gentle to moderate winds will continue north 
of 07N with seas 5 ft or less through Thu night. Moderate to 
fresh SW monsoonal winds will prevail to the S of 07N through mid
week. Slight to moderate seas will continue, highest offshore 
Ecuador to the Galapagos Islands, before seas build slightly 
region-wide in S-SW swell beginning Wed. Active weather will
continue across the waters of western Panama and Costa Rica
through Wed associated with a tropical wave passage.


The remnants of T.C. Fourteen-E are centered near 15.5N129.5W as
a 1010 mb swirl of mostly low level clouds. Fresh to strong 
winds are noted across the northern semicircle with the low, with
seas to 10 ft. Scattered moderate to strong convection has
intensified in recent hours near the ITCZ to the south, from 09N
to 12N between 126W and 130W.

A surface trough continues along 131W-132W from 24N to 27N. 
Scattered shallow convection is east of the trough to 128W. 
Associated winds are moderate with remnant 5 ft seas in mixed 
swell across the N side. Elsewhere N of 20N and W of 120W, 
anticyclonic winds are moderate or weaker, and seas are 4-6 ft. S
of 20N and to the west of the remnants of Fourteen, the modest 
pressure gradient between a weak high pressure ridge along 27N 
and lower pressure near the ITCZ is yielding moderate ENE trade 
winds and seas of 5 to 7 ft in mixed N and SE swell.

New southeasterly swell has moved across the equator, and is  
building seas to around 8 ft to 01N and W of 110W, and will 
propagate northwestward over the next 48 hours.

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 surface trough near 131W will gradually shift W-SW and 
dissipate through Tue. A cold front approaching the far NW waters
will sink slowly into those NW waters tonight through Wed night
and stall. High pressure north of the front will increase the
pressure gradient to the west of 125W, and freshen the winds Tue
through Thu. This will also coincide with the arrival of large 
NW to N swell generated across the NE Pacific in recent days. 
This swell will push into the northern waters this afternoon, 
building seas to 7-11 ft N of 10N and W of 115W by the middle of 
the week. Elsewhere, weak high pressure will prevail N of the 
monsoon trough and E of 120W through Wed and yield moderate or 
weaker winds. 

Looking ahead, another pulse of SE swell will enter the area S 
of the equator by mid week and spread N through Fri.