AXPZ20 KNHC 250915

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon May 25 2020

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.


The axis of a tropical wave is along 92W north of 04N to inland the western section of Guatemala. It is moving westward at about 12 kt. Isolated showers and thunderstorms are increasing within 120 nm east of the wave axis from 05N to 10N.


The monsoon trough axis extends from a 1009 mb low centered over northwestern Colombia near 11N74W westward to across northern Panama and to the coast at 09N84W. It continues west-northwest to 11N96W to low pressure of 1009 mb near 11N107W, then to low pressure of 1011 mb near 10N121W and to a 1012 mb low near 10N132W, where overnight scatterometer data indicates that it transitions to the ITCZ to beyond the area at 09N140W. Scattered moderate to strong convection is seen from 06N to 09N between 103W-107W. Scattered moderate to isolated strong convection is within 180 nm south of the trough between 86W-89W and also between 99W-101W. Similar activity is within 30 nm south of the trough between 108W-110W. Scattered moderate convection is within 120 nm north of the trough between 131W-132W.


A ridge extends from high pressure centered near north of the area near 34N138W southeastward to the Revillagigedo Islands, while low pressure is present over Mexico. The pressure gradient between these features is supporting generally gentle to moderate northwest winds west of Baja California. Light to gentle winds are elsewhere. Wave heights have subsided a little to 5-6 ft west of Baja California and are 4-5 ft elsewhere over the open waters off Mexico. Wave heights are in the 1-2 ft range in the Gulf of California.

The area of high pressure over the Pacific forecast waters will weaken through Wed maintaining winds off the coast off Baja California at gentle to moderate speeds.

Agricultural fires in Mexico continue to produce hazy skies from near the Tehuantepec region to northwestern Mexico.


Gentle to moderate south to southwest monsoon flow continues south of 10N, with light to gentle winds north of the monsoon trough. Wave heights in the 4-6 ft range are due to southwest swell.

Gentle to moderate monsoon flow will continue over the next few days. Moderate long-period southwest will continue through Wed, with wave heights building to near 8 ft to the southwest of the Galapagos.

A broad area of low pressure is expected to form a few hundred miles south of the coasts of southern Mexico, Guatemala and and El Salvador late in the upcoming week. This will bring unsettled weather in the form of increasing showers and thunderstorms, with gusty winds, to those waters.


High pressure of 1027 mb is centered north of the area near 34N138W. The pressure gradient between the associated ridging and low pressure in the vicinity of the ITCZ and within the monsoon trough is supporting gentle to moderate northeast winds north of the ITCZ/monsoon trough. Gentle to moderate south to southwest winds are south of the monsoon trough, while gentle to moderate southeast winds are south of the ITCZ. Wave heights are in the 5-7 ft range over the area. Scatterometer data from Sun afternoon revealed a few areas of weak lows embedded within the monsoon trough. One low with a pressure of 1009 mb is near 11N107W, another one with a pressure of 1011 mb is near 10N121W and a 1012 mb low is near 10N132W. Scattered showers and thunderstorms are within 120 nm in the SW and W quadrants of the low near 11N107W, while similar activity has recently developed within 90 nm in the NW quadrant of the low near 10N132W.

Southerly flow to the south of the monsoon trough will strengthen slightly through Tue night roughly between 102W-118W. This will help build wave heights to 8-9 ft over these waters.

The area of high pressure will weaken through Wed as surface troughing develops across the north-central waters. Low pressure is forecast to develop by Wed along the troughing near 25N130W. The troughing may transition to more a frontal structure type feature.

$$ Aguirre