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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 290346
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Thu Jul 29 2021

Tropical Weather Discussion for the eastern Pacific Ocean from
03.4S to 30N, east of 120W including the Gulf of California, and
from the Equator to 30N, between 120W and 140W. The following
information is based on satellite imagery, weather observations,
radar, and meteorological analysis.

Based on 0000 UTC surface analysis and satellite imagery through
0330 UTC.

...SPECIAL FEATURES...

Low pressure of 1007 mb is centered along the monsoon trough 
near 14N120W. Latest satellite imagery shows numerous moderate 
convection within 150 nm of the low in the E quadrant. Scattered
moderate to isolated strong convection is within 180 nm of the 
low in the SE quadrant and within 150 nm of the low in the SW 
quadrant. Scattered moderate convection is within 30 nm of a line
from 17N118W to 17N120W. The low remains fairly elongated as it
being impinged upon by light northwest shear aloft. The latest 
ASCAT pass over the low indicated fresh to strong southwest winds
in the southeast quadrant and fairly light to moderate winds on 
its northern periphery. This low pressure has a medium chance of 
becoming a tropical cyclone during the next 48 hours. Even it 
does not expect strong winds and seas to 8 to 9 ft near this low 
pressure over the next few days. Please see the latest NHC 
Tropical Weather Outlook at www.hurricanes.gov for more details.

...TROPICAL WAVES...

A new tropical wave has entered the far eastern part of the area
with its axis along 78W north of 03N. It is moving westward 
at about 18 kt. An isolated thunderstorm is over southern Panama
near 08N78W. Otherwise, no deep convection is noted with this 
wave.

A tropical wave with its axis along 94W extends from the Gulf 
Tehuantepec region to near 04N. It is moving westward at 10 to 
15 kt. Scattered moderate to strong convection is increasing 
within 60 nm east of the wave north of 14N to inland southeastern
Mexico. Scattered moderate convection is also west of the wave 
north of 13N to inland Guatemala and between 92W-93W.

A tropical wave has its axis near 124W from 03N to 18N, moving 
westward at 10-15 kt. No significant convection is evident near 
this tropical wave.

A tropical wave has axis along 137W from 03N to 16N. It is 
moving westward at 10-15 kt. Scattered moderate to isolated 
strong convection is noted from 08N to 14N between 137W and 
140W, and also east of the wave from 08N to 12N between 131W-
137W. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends from the coast of Colombia near 09N77W
to across northern Panama and central Costa Rica continuing to
10N94W to low pressure near 12N105W 1007 mb to 10N114W and 
northwest to 10N125W to low pressure near 14N120W and to 
10N126W. The ITCZ continues from 10N125W to beyond 10N140W. In 
addition to the convection described in the Tropical Waves 
section above, scattered moderate to isolated strong convection 
is seen within 120 nm south of trough between 120W-122W and 
within 60 nm south of trough between 100W-108W. Scattered 
moderate convection is within 120 nm south of trough between 97W-
100W and within 30 nm of ITCZ between 129W-133W.

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Fresh north gap winds are pulsing across the Gulf of Tehuantepec,
between relatively higher pressure to the north of the region and
lower pressure farther south. Light to gentle variable winds are
elsewhere with seas mainly to 3 to 5 ft due to a south to
southwest swell.

Farther north, a relatively weak pressure gradient supports 
gentle to locally moderate northwest winds over the Baja 
California offshore waters with seas in the 3 to 5 ft range in SW
swell. 

For the forecast, high pressure north of the area and lower 
pressure farther south will support pulses of gap winds across 
the Gulf of Tehuantepec and off western Oaxaca tonight and Thu 
night. Mostly moderate winds and seas will persist elsewhere. 
Looking ahead, seas will build off southern Mexico starting late 
Sat due to increased southerly swell. A broad area of low pressure
has formed several hundred miles offshore the southwestern coast
of Mexico. Environmental conditions are forecast to be conducive
for continued gradual development, and a tropical cyclone could 
form this weekend or early next week while the system moves 
westward or west-northwestward.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, 
COLOMBIA, and WITHIN 750 NM OF ECUADOR...

Gentle to moderate south to southwest winds will remain 
south of the monsoon trough through the forecast period along 
with a southwest swell that will build seas to 5-7 ft. Moderate 
to locally fresh northeast to east winds will continue over the 
Papagayo region and waters downstream from there through Sun, 
then diminish slightly Sun night into early next week. Seas of 
3-6 ft due to a southwest swell will change little over Gulf of 
Papagayo region during the next few days.

For the forecast, fresh to strong gap winds may pulse tonight 
across the Gulf of Papagayo and again Thu night into Fri. 
Elsewhere, gentle to moderate south to southwest winds will 
dominate the waters south of the monsoon trough through the 
forecast period along with southwest swell. The weather over the 
offshore waters of Costa Rica and Colombia will be unsettled over
the next few days due to instability associated with passing 
tropical waves.

REMAINDER OF THE AREA...

See the Special Features section above for details on a low
pressure system that has potential for tropical cyclone 
formation.

An upper trough is along 123W and north of 25N. This feature is
weakening the subtropical ridge and creating northwest shear 
over the Special Features low pressure system. Over the 
eastern part of the area, low pressure area is centered near 
12N105W with an estimated pressure of 1007 mb. Latest satellite 
imagery shows that this low pressure area is broad, but 
convection with it has increased during the past few hours. This 
convection consists of the scattered moderate to isolated strong 
type intensity within 270 nm of the low in the SE quadrant and 
within 180 nm of the low in the SW quadrant. Scattered moderate 
convection is from 08N to 10N between 108W-110W, and within 60 
nm of line from 12N104W to 12N106W. Latest ASCAT data from a few 
hours ago revealed a few moderate to fresh northeast winds on 
the north side of the low, but mostly gentle to moderate winds 
are evident and seas are likely no more than six feet near the 
low.

Elsewhere, relatively weak high pressure is present with the 
associated gradient allowing for generally moderate northeast 
trades to persist north of the monsoon trough and moderate south
to southwest winds farther south, with 5 to 7 ft seas in mixed 
swell in most areas. Larger southerly swell is noted south of the
equator. 

$$
Aguirre