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 hurricanes.gov 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.

$$ Reinhart