000
AXPZ20 KNHC 181603
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1427 UTC Wed Apr 18 2018

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
1515 UTC.

...SPECIAL FEATURES...

A gale warning is now in effect for the Gulf of Tehuantepec, 
with northerly winds expected to reach minimal gale force in 
about 36 hours. High pressure building over the northern Gulf of
Mexico Thu night is expected to tighten the gradient across the 
Isthmus of Tehuantepec and funnel very strong winds over the 
Gulf of Tehuantepec through Fri, producing 8 to 12 ft wind- 
driven seas downstream to about 14N. Winds will taper to fresh
speeds by Sat afternoon.

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

A surface trough extends from 07N78W to 05N82W to 07N89W to 
07N91W. The ITCZ continues from 07N91W to 07N96W to 08N109W to 
04N123W to 06N131W to beyond 07N140W. An expansive area of active
convection is associated with the ITCZ. Scattered Moderate and 
isolated strong convection is present within 60 NM either side of
the trough axis from 81W and 89W, from 05N to 08N between 93W 
and 99W and within an area bounded by 08N100W to 04N122W to 
16N118W to 13N108W to 08N100W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Moderate NW to N winds and seas of 6 to 8 ft in NW swell are 
noted for the offshore waters. A cold front will reach northern 
Baja California on Thu, then weaken as it moves S-SE through Fri.
Moderate NW to N winds will dominate the waters W of Baja 
California the next two days, then freshen behind the front Thu 
night and Fri as a tight pressure gradient develops between a 
ridge over northern waters and lower pressure in the SW CONUS and
NW Mexico. NW winds in the Gulf of California will become gentle
to moderate through Fri. Seas will gradually subside today, with
seas falling to 5-7 ft by tonight. See special features section 
for details about gale force winds expected in Gulf of 
Tehuantepec Thu night and Fri morning.

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

Gulf of Papagayo: Pulsing nocturnal NE-E winds are expected 
across and downstream of the Gulf of Papagayo through Fri. 

Gulf of Panama: Fresh northerly winds are expected across the 
Gulf of Panama through tonight, with seas of 4-6 ft.

Elsewhere, light to gentle winds are expected through Sun, with 
a weak surface through meandering west of Panama along 06N-08N. 
Seas in the 3 to 5 ft range will continue over most of the area. 
Cross equatorial SW swell will mix with residual swell from 
Papgayo today through Fri, and raise seas to 5-7 ft S of 10N.

REMAINDER OF THE AREA... 

High pressure centered northwest of the forecast area ridges SE 
across the northern forecast waters. The ridge will weaken some 
during the next 24-48 hours, and then will be reinforced by stronger
high pressure building in behind a cold front on Fri and Sat. 

NW swell continues to propagate SE through the forecast waters, 
with max seas of 8-9 ft. This swell is mixing with NE swell 
generated previously from the Tehuantepec area. 7 ft or greater 
seas cover most of the area W of 100W this morning.

Cross equatorial SW swell moving into southern forecast waters 
will dominate the waters S of 04N between 95W and 120W today. 
Seas are forecast to subside to 8 ft or less across most of the 
area W of 120W by late tonight.

$$
CAM