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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 211024

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Wed Aug 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 
0845 UTC. 


A 1007 MB low pressure system is located near 14.5N104.5W, or 
about 250 nm south of Manzanillo, Mexico. This area of low 
pressure is embedded within a large area of cyclonic winds that 
cover the area between 96W and 112W. A large area of showers and 
thunderstorms associated with this broad circulation continues 
tonight, with a cluster of strong thunderstorms persisting near 
the low. and suggesting that it is slowly becoming better 
organized. Environmental conditions are favorable for further 
development, and tropical cyclone is expected to form within the 
next 48 hours. Global models suggest that gale force winds will 
develop by Thu afternoon associated with this low. Currently, 
numerous moderate and scattered strong convection is located 
within 180 nm across the NW and 120 nm across the SE 
semicircles, while scattered moderate to strong convection is 
elsewhere from 06.5N to 18N between 94W and 118W. The low is 
expected to move WNW at 10 to 15 kt through 24 hours, running 
parallel and several hundred miles offshore the coast of central 
Mexico, and then turn more NW and offshore of Baja California. 
This system could still produce locally heavy rainfall leading 
to flash flooding across the coastal states of Mexico from Oaxaca 
to Jalisco over the next couple of days. Refer to the latest NHC 
High Seas Forecast under AWIPS/WMO headers MIAHSFEP2/FZPN03 KNHC 
for more details on the forecast of this low.


A tropical wave extends from the eastern Bay of Campeche S-SE 
across far southeast Mexico and Guatemala to near 07N89W. 
Scattered to numerous moderate to strong convection is occurring 
ahead of this wave from 10N to the Mexican coast between 93W and 
100W, while scattered moderate isolated strong convection is 
elsewhere behind the wave from 05.5N TO 10N between 81W AND 93W.


The monsoon trough extends from 10N73W TO 08N80W TO 11.5N91W to 
low pressure near 14.5N104.5W to 11.5N110W to 16.5N120W to low 
pressure near 16N123.5W to near 12N139W. Scattered strong 
convection is noted from 03N to 08.5N E of 79.5W. Scattered 
moderate to strong convection is within 120 nm either side of 
the trough between 130W and 140W.


Please see the Special Features section for more details about 
the low pressure area offshore of Manzanillo.

The pressure gradient between high pressure northwest of the 
area and low pressure across the northern Gulf of California is 
producing fresh to locally strong NW winds offshore of Baja 
California N of 25N this morning, and is expected to continue 
today before retreating to the NW late this afternoon and 
evening. This will maintain seas of 5-7 ft in mixed NW to N 
swell. Low pressure over the U.S. Great Basin will induce fresh 
to strong SE to S winds over middle and north portions of the 
Gulf of California Wed evening through Fri.

A middle to upper level trough extending from the SW Gulf of 
Mexico WSW across central Mexico has maintained unstable upper 
level conditions and is supporting ongoing moderate to strong 
convection across the waters from Cabo Corrientes to the 
Mazatlan area. This convection is expected to diminish this 
morning. The trough will remain in place through tonight and is 
expected to support another round of late afternoon and night 
time convection across this area again Wed. 

Overnight scatterometer data showed E to SE winds of 20 kt 
between the low pressure center S of Manzanillo to the coast 
between Puerto Angel and Manzanillo. Seas in this region are 
ranging from 6 to 10 ft. Look from fresh to strong E to SE winds 
and seas remaining in the 6-9 ft range through Thu as the low 
moves parallel to the coast. Very active convection also across 
this area will have the potential for strong wind gusts and 
frequent lightning.


A weak pressure gradient is expected to produce only gentle to 
moderate winds across the region for the next several days. Long 
period cross equatorial SW swell will reach the waters between 
Ecuador and the Galapagos Islands today, building seas to 6 to 7 
ft late today into Thu. 


A 1022 mb high pressure located near 30N133W extends a ridge 
across the northern forecast waters. This system will remain 
nearly stationary over the next 48 hours producing mainly gentle 
to moderate winds N of 20N and W of 110W. The pressure gradient 
between the ridge and lower pressures in the vicinity of the 
monsoon trough will result in moderate to fresh trade winds S of 
20N. The remnants of a low pressure center persist along the 
monsoon trough near 16N123.5W. fresh winds to around 20 kt 
surrounding this low are combining with mixed swell across the 
region to produce seas of 6-8 ft from 15N to 17.5N between 124W 
and 130W. This low will shift W and weaken through Fri. 
Elsewhere winds are expected to increase S of the monsoon trough 
through Thu night, particularly between 105W and 120W, in 
response to the developing low pressure system offshore of 
Manzanillo. As the monsoon through continues to lift northward 
fresh to strong SW monsoonal winds will create wind waves that 
will combine with SW swell to produce seas of up to 10 ft S of 
15N between 100W and 120W through Thursday. Some northerly swell 
will cross south of 30N to near 25N around 120W Thursday, with 
seas around 8 feet expected.