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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 211515

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1515 UTC Sun Jul 21 2019

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
1500 UTC. 


Gale Warning: Recent satellite imagery indicates that a low 
pressure system located near 12.5N116W is gradually becoming 
better defined. Thunderstorm activity has been steadily 
increasing and becoming better organized, and a tropical 
depression or a tropical storm is expected to form during the 
next day or so. Scattered moderate convection is noted within 120
nm NW semicircle of the low. The disturbance is forecast to move
generally northwestward at around 10 mph, remaining well 
offshore the coast of Mexico. Winds are expected to increase to 
minimal gale force by late tonight as the system becomes better 
organized, and there is a high chance of tropical storm 
development. The system will pass west of Clarion Island Mon 
night and Tue, with 8-10 ft seas expected near the island. 

Please see the latest eastern North Pacific Tropical Weather 
Outlook at for more information.


A tropical wave with axis near 80W extends southward from the
western Caribbean Sea into the far eastern Pacific. Numerous
moderate scattered strong convection is noted from 03N to 07N
east of 82W.

A tropical wave with axis near 95W is moving west around 10-15 
kt. Scattered moderate isolated strong convection is noted from
05N to 08N between 91W and 98W.

A tropical wave with axis near 110W is moving west around 10-15 
kt. Scattered moderate convection is noted from 14N to 16N within
120 nm of the wave axis. 

A tropical wave with axis along 120W is moving west around 10-15 
kt. Scattered weak convection is noted from 09N to 11N within 
120 nm west of the wave axis. 


The monsoon trough extends from 07N77W to 08N100W to 15N110W to 
07N124W. The ITCZ extends from 07N124W to 03N140W. Scattered
moderate convection is noted within 180 nm of the monsoon trough
between 82W and 100W, and within 120 nm north of the ITCZ between
125W and 134W.


The primary forecast concern through mid week will be the track
of the developing low pressure system near 12.5N116W. The low 
pressure is forecast to pass west of Clarion Island by Tue 
morning as a gale center or tropical storm. Seas of 8-10 ft are 
expected to impact the waters near Clarion Island late Mon into 
Tue as the low moves past. Please see the Special Features 
section above for more information on this system.

A mid-level trough just west of Baja California is supporting
scattered showers and thunderstorms over the offshore waters
between Cabo San Lucas and Cabo Corrientes, including the
entrance to the Gulf of California. Weak ridging over the 
northern waters is supporting gentle to moderate NW winds off 
Baja California, and gentle to moderate SE flow over the Gulf of 
California. Little change is expected over the next couple days. 
Weak high pressure building in the wake of the aforementioned low
will enhance winds to fresh speeds along the coast south of Cabo
Corrientes Mon night into Tue. 

Farther south, an overnight scatterometer pass showed fresh
northerly gap winds over the Gulf of Tehuantepec. These winds 
will diminish later this morning, but brief pulses to 20 kt are 
possible in this region through the middle of this week.


The pressure gradient across Central America is maintaining 
fresh to strong NE to E winds near and downstream of the Gulf of 
Papagayo. Fresh to locally strong winds will continue pulsing 
across the Gulf this week with the strongest winds occurring 
during the overnight and early morning hours. Seas will peak 
around 8 ft each morning downstream of the Gulf. Elsewhere, 
moderate winds south of the monsoon trough will strengthen to 
fresh speeds tonight and Mon, with seas building to 8-9 ft off 
the coast of Panama and Colombia. Looking ahead, seas will build 
to 8 ft or greater over the southern waters Wed through Thu in 
long period S to SW swell.


Overnight scatterometer data showed a broad area of fresh to
strong winds associated with elongated low pressure along the
monsoon trough over the waters between 111W-117W. Please see the 
Special Features section above for more information on the high 
potential for tropical cyclone development in this region.

Elsewhere, weak low pressure centered near 18N134W will open up 
into a trough later today and likely dissipate tonight. Moderate 
trade winds are occurring roughly north of 20N and west of 130W 
between weak ridging north of the area and the low pressure 
previously described. The latest altimeter data suggests 8 ft 
seas in southerly swell remain just south of the forecast area.