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 Eastern Pacific Basin Tropical Discussion Atlantic | East Pacific 
AXPZ20 KNHC 220933

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Wed Sep 22 2021

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
0930 UTC.


A Gale Warning is in effect for the Gulf of Tehuantepec tonight 
into Thu. An early season cold front entering the NW Gulf of 
Mexico this morning will reach from the NE Gulf to central Bay 
of Campeche by late Thu. High pressure building in the wake of 
the front across the eastern slopes of the Sierra Madre Mountains
and the western Gulf of Mexico will support the gap wind event in
Tehuantepec, which is forecast to reach minimal gale force tonight
into Thu. Seas are forecast to build to 9-11 ft with this event.
Please, refer to the latest NWS High Seas Forecast issued by the
National Hurricane Center at website 
https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details.


The axis of a tropical wave is along 109W and from 06N to 18N, 
moving west at 10 to 15 kt. Scattered moderate convection is 
noted from 07N to 12N between 102W and 113W.

The axis of a tropical wave is along 119W from 10N to 20N, 
moving west at 10 to 15 kt. A 1010 low pressure is along the wave
axis near 15N119W. Scattered moderate convection is from 10N to 
21N between 114W and 124W.

The axis of a tropical wave is along 138W from 05N to 18N, 
moving west at 10 to 15 kt. A 1010 low pressure is along the 
wave axis near 09N138W. Scattered moderate convection is seen 
from 07N to 11N W of 136W. 


The monsoon trough extends from 10N86W to 11N106W to 1010 mb low
pressure located near 15N119W to 13N123W. The ITCZ begins near 
10N121W and continues to 06N131W to beyond 10N140W. Aside from 
the convection associated with the tropical waves, scattered 
moderate convection is N of 01N E of 87W, and N of 11N between
86W and 96W.


Surface ridging over the NE Pacific open waters extends to the
offshore waters of Baja California Norte and continues to provide
gentle to locally moderate northely winds along the Baja California
offshore waters, the Gulf of California, and SW Mexico offshore
waters. Seas in these regions are up to 5 ft, except in the gulf
where the seas are up to 3 ft. Otherwise, fresh to strong winds 
continue in the Gulf of Tehuantepec with seas to 7 ft. 

For the forecast, winds in the Gulf of Tehuantepec will increase
to near gale force today and reach gale force briefly tonight. 
Please, see the Special Features section for more details.
Surface ridging will continue to dominate the offshore waters of
Baja California supporting mainly gentle to moderate NW winds 
through Sun. Light to gentle variable winds will dominate over 
the SW Mexico offshore waters. In the northern Gulf of 
California, a surface trough will support fresh to locally strong
southerly winds Thu night through Fri night. 


Gentle to moderate southerly winds will prevail across the offshore
waters of Costa Rica, Panama, Colombia and Ecuador during the 
forecast period, with seas of 4-6 ft in SW swell. Mainly light 
and variable winds are forecast across the offshore waters from 
Guatemala to northern Costa Rica, with seas of 3-5 ft also in SW


A broad and elongated area of low pressure located several hundred 
miles SW of the southern tip of the Baja California peninsula 
continues to produce disorganized showers and thunderstorms. 
Environmental conditions are somewhat conducive for development, 
and a short-lived tropical depression could form on Thursday or 
Friday while the low moves generally NW. This system is forecast
to move over cooler waters and into an environment of stable air
and strong upper-level winds this weekend, which should inhibit 
further development. The latest Tropical Weather Outlook gives 
this system a medium chance of tropical cyclone formation 
through 48 hours. Please, refer to the latest Tropical Weather 
Outlook, at www.hurricanes.gov for more details.

The northern forecast waters remain under the influence of a 
surface ridge. The pressure gradient between the ridge and lower
pressures near the monsoon trough/ITCZ supports moderate to 
locally fresh N to NE winds N of 10N and W of 120W, with seas of
5-7 ft, except for 8 ft W of 137W. Winds across this area will
diminish over the weekend.


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