000
AXPZ20 KNHC 182020
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Tue May 18 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.

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

The monsoon trough extends from 08N78W to 10N97W. The ITCZ 
extends from 10N97W to 08N125W to 09N140W. Scattered moderate 
convection is noted from 05N to 07N between 80W and 85W. 
Scattered moderate to isolated strong convection from 07N to 10N
between 90W and 97W. Scattered moderate convection is noted from
10N to 12N between 116W and 118W, from 09N to 10N between 122W 
and 124W, and from 09N to 10N between 132W and 134W.

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A ridge extends from high pressure centered near 35N145W southeastward
toward Socorro Island. A recent scatterometer satellite pass 
indicated moderate to fresh NW winds off the coast of Baja 
California, between the ridge and troughing over northwest 
Mexico. An altimeter satellite pass from a few hours ago 
indicated seas are mostly 5 to 7 ft off Baja California. Light 
breezes and slight seas are noted over the Gulf of California. 
Farther south, another scatterometer pass indicated light to 
gentle W to NW winds are evident over the offshore waters of 
southern Mexico, south of 20N. A concurrent altimeter pass showed
seas of 5 to 7 ft as well. This is likely due to ongoing longer 
period SW swell.

For the forecast, the high pressure centered west of Baja 
California will continue to support mainly moderate to fresh NW 
winds north of Cabo San Lazaro into Thu. Winds will increase to 
fresh to strong speeds mainly west of central and northern Baja 
California and over the northern Gulf of California late Thu into
Fri as stronger high pressure builds southeastward across the 
waters west of Baja California behind a weak frontal boundary 
moving across southern California and the far northern Baja 
California Norte. Meanwhile, long period SW swell will persist 
over Mexican offshore waters, especially south of Cabo 
Corrientes, with another set arriving by Fri. Looking ahead, a 
trough or low may form well south of the Gulf of Tehuantepec 
region.

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

A recent scatterometer pass confirmed moderate NE to E gap winds
in the Gulf of Papagayo. A concurrent altimeter satellite pass
showed 5 to 7 ft seas, approaching 8 ft in the gap wind plume.
These seas include a dominant component of long period SW swell,
which is supporting mainly 5 to 7 ft seas across the offshore
areas across the region. The upper level pattern is supporting a
few showers and thunderstorms along the monsoon trough, 
impacting the waters off western Panama and beyond 180 nm off the
coasts of Nicaragua, El Salvador, and Guatemala. 

For the forecast, seas of 5-7 ft will change little into late in
the week. Long period cross- equatorial southerly swell will 
continue to impact the offshore forecast waters through Fri 
night, then begin to subside on Sat. Seas between Ecuador and 
the Galapagos Islands will begin to build to 8 ft or higher on 
Wed as additional pulses of long- period southwest swell begin to
propagate through those waters. Looking ahead, fresh gap winds
are possible through the Gulf of Papagayo by Sat.

REMAINDER OF THE AREA...

The subtropical ridge continues to dominate the waters north of 
15N. The pressure gradient between it and comparatively lower 
pressures in the tropical zone area is leading to a large area of
moderate to fresh trade winds north of the ITCZ, with seas up to
8 ft. Gentle to moderate trade winds are noted elsewhere, with 
seas in the range of 6-7 ft mainly due to a southerly swell 
component. 

For the forecast, reinforcing high pressure will allow trade
winds to increase north of the ITCZ and west of 125W, with seas 
building to 9 ft. Seas will continue to be 6 to 7 ft east of 125W
as a new round of cross-equatorial SW swell brings seas in excess
of 8 ft as far as 10N by Thu, before subsiding into early next
week. Looking ahead, weak low pressure is expected to form well 
south of the Tehuantepec area by Fri, but not intensify as it 
tracks westward along 10N between 95W and 105W Fri into early 
next week.$$
Christensen