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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 210929

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
929 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 0600 UTC surface analysis and satellite imagery through
0900 UTC. 


Gale warning: Recent satellite imagery indicates that a broad 
and elongated low pressure area located near 12N115W continues to
become better organized. Environmental conditions are expected 
to be conducive for additional development of this system, and a 
tropical storm is likely to form within the next day or two. 
Scattered moderate to isolated strong convection is ongoing 
within 180 nm in the northern semicircle of the low pressure. 
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 through late Mon. This 
disturbance is forecast to move generally northwestward at around
10 mph away from the coast of Mexico, although winds to gale 
force may pass within 120 nm west of Clarion Island by early 
Tue, with seas to 10 ft reaching the island.

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


A tropical wave with axis near 94W is moving west around 15-20 
kt. Scattered moderate convection is noted along the monsoon
trough near the wave axis, from 06N to 08N between 90W and 97W. 

A tropical wave with axis near 109W is moving west around 10 kt.
Scattered convection is noted north of the tropical wave from 18N
to 20N between 105W and 110W. 

A tropical wave with axis along 119W is moving west at 10 kt, 
related to the low pressure near 12N115W.


The monsoon trough extends from 07N77W to 09N100W to 14N110W to 
the low pressure near 12N115W to 06N125W. The ITCZ extends from
06N125W to 05N140W. Beyond than what is described in the Special
Feature and Tropical Wave sections above, numerous moderate to
scattered strong convection is noted from 03N to 07N east of 82W.


Weak ridging is supporting gentle to moderate NW winds off Baja
California, and light to gentle southerly flow over the Gulf of
California. The main forecast issue into mid week will be the
development and track of the developing low pressure area 
currently near 12N115W. The low pressure is forecast to make its 
closest point of approach west of Clarion Island by early Tue as 
a gale center or tropical storm. Seas to 10 ft are expected to
impact the Clarion area late Mon into Tue as the low moves past.
In addition, the track of the low will allow regional high
pressure to build east of the Revillagigedo Islands, resulting in
a slight enhancement of NW winds off the coasts of Colima and
Jalisco south of Cabo Corrientes late Mon into Tue. 

Farther south, a recent scatterometer pass showed fresh gap 
winds over the Gulf of Tehuantepec. This will diminish through
the morning, but brief pulses to 20 kt are possible in this
region through the remainder of the period mainly overnight.


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


A Kelvin wave moving across the central Pacific is supporting 
weak surface low pressure near 18N134W. This system is likely 
producing a small area of fresh winds with seas to 9 ft based on 
the latest model guidance. This low will rapidly weaken through 
tonight as it drifts northward while the Kelvin wave continues 
propagating eastward. Elsewhere, moderate trade winds are 
roughly north of 20N and west of 135W between weak ridging north
of the area and the aforementioned low.