000 AXPZ20 KNHC 192204 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2035 UTC Wed Dec 19 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 1800 UTC surface analysis and satellite imagery through 2045 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front is entering the Bay of Campeche. The front will continue sweeping SE across the Gulf of Mexico tonight through Thu. High pressure building S a long the Sierra Madre Oriental in the wake of the front will generate a tight pressure gradient over the area and usher in the next gale force gap wind event. Winds will rapidly increase to gale force by late Thu and to strong gale force by Fri morning. The plume of strong gap winds will reach at least 500 nm to the south and SW of the Gulf of Tehuantepec by late Fri, with seas building as high as 19 ft with the area of strong winds. The gales will persist through Fri night, then diminish on Sat as the high pressure north of the area weakens and shifts east. Fresh to strong gap winds will then persist across the Gulf of Tehuantepec through Sun night. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 06N74W to 05N79W to 06N88W to 05N97W. The ITCZ continues from 05N97W to 05N117W to beyond 08N140W. Scattered moderate and isolated strong convection is present from 06N to 10N W of 130W. Scattered moderate convection is seen from 04N to 07N between 86W and 91W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more on the impending gale force gap wind event over the Gulf of Tehuantepec. Large NW swell continues to impact the forecast waters, with seas in the 10 to 13 ft range over the waters off the Baja California Peninsula to the Revillagigedo Islands. The swell are beginning to decay but will remain high enough to produce hazardous seas for mariners and create large and powerful surf along the Pacific reefs and beaches. This high surf could also produce coastal flooding and beach erosion in many exposed locations from southern California to western Mexico. This swell will be reinforced by another round of NW swell to 12 ft reaching Guadalupe Island and the northern coast of Baja California Thu morning. This next batch of swell will decay below 12 ft by Thu evening as seas remain in the 8 to 10 ft range over the open waters off Mexico west of 110W through Sat. Long period NW swell along the coast of Mexico will continue to decay and allow seas top subside below 8 ft for all of the offshore waters by Sat evening. High pressure building over the Great Basin will support fresh to strong winds along the Baja coast of the central Gulf of California through Thu morning, with seas peaking around 8 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: A cold front will move across the SW Caribbean on Fri morning. Strong N winds behind the front will funnel through the Gulf of Papagayo, increasing to near gale force by late Fri night. This event will peak on Sat as winds reach minimalgale force. A tight pressure gradient between high pres building behind the front and lower pres in the SW Caribbean will support the continuation of the gap wind event through Sun night. Seas are expected to peak near 12 ft on Sat morning. Winds and seas will gradually diminish Sun night through Mon night. Fresh to locally strong N winds are expected over the Gulf of Panama Sat night through early on Mon. Winds could become strong Sat night and Sun as seas peak around 8 ft. Elsewhere, gentle to moderate winds will persist, with seas in the 4 to 7 ft range. REMAINDER OF THE AREA... High pressure of 1027 mb is centered north of the area near 34N126W. The pressure gradient between this area of high pressure and lower pressure in the vicinity of the ITCZ will support moderate to fresh trade winds north of the ITCZ to around 20N. A sharp upper-level trough will cutoff west of the area, and induce a nearly stationary trough along the ITCZ west of 135W by late Thu. This will tighten the pressure gradient further over this area. Trade winds will increase from fresh to strong N of the ITCZ to near 15N and west of 135W by late Thu into early Fri. NW swell continues to prevail across the discussion area. Seas of 8 ft or greater are noted W of 100W. Another set of NW swell has entered the NW waters, with seas of 12 to 15 ft noted NW of a line from 30N130W to 21N140W. Seas will subside N of 20N and W of 120W tonight through Sat. $$ CAM