000 AXPZ20 KNHC 261605 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Nov 26 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 1545 UTC. ...SPECIAL FEATURE... The pressure difference between strong high pressure building southward along the eastern slopes of the Sierra Madre Occidental in Mexico and lower pressure south of Mexico will induce a gap wind event over the Gulf of Tehuantepec this afternoon. North winds of 20 to 30 kt across the Gulf will quickly begin shortly after 18Z this afternoon, reaching minimal gale force at or near 21Z. Seas will reach the range of 8 to 11 ft this afternoon, and continue to build to the range of 10 to 14 ft early Tue. The pressure gradient will relax beginning late Tue and through Wed night as the strong high pressure shifts eastward from Mexico to over northern Gulf of Mexico. This process will allow for winds across the Gulf to diminish to mainly moderate to fresh and for seas to subside to below 8 ft during this time. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1009 mb low over Colombia centered at 06N75W, west-northwestward to 06N77W to 08N90W to 12N100W to a 1009 mb low near 11N104W to a 1009 mb low near 09N109W and to another 1009 mb low near 09N119W and to 06N128W, where latest scatterometer data indicates the ITCZ begins and continues to 06N134W to 08N140W. Numerous moderate to strong convection is seen within 120 nm north of the ITCZ west of 136W. Scattered moderate convection is within 180 nm south and 60 nm north of the trough between 77W and 80W. Similar convection is within 60 nm north of the trough between 87W and 95W, and within 60 nm south and 30 nm north of the trough between 115W and 119W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Light to gentle northwest to north winds along with seas of 5 to 7 in a NW swell are west of the Baja California Peninsula for the time being. Wave model guidance depicts that an extensive set of long- period NW swell associated with a cold front presently well northwest of the discussion area will reach the waters west of Baja California Norte beginning late Tue night into Wed morning and the southern tip of Baja California Sur by late Wed night into Thu. The wave guidance shows seas building to the range of 8 to 12 ft with this upcoming swell event, with the highest of these seas expected north of about 26N. Elsewhere, A 1009 mb low analyzed along the monsoon trough near 11N104W may lift out of the monsoon trough during the next couple of days and slowly drift in a north to northwest direction, possibly reaching near 13N105W by early Wed, then track north-northeastward to near 14N103W by Thu night. The gradient will tighten within about 90 to 120 nm to its east, with resultant fresh to strong winds and seas to 9 ft beginning late Tue night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Enhanced infrared imagery from GOES-E continues to show intermittent plumes of volcanic ash originating from the Fuego volcano in southern Guatemala. The plumes are tracking in a west-northwest direction and become diffuse as they cross into SW Mexico and near the coast of Chiapas. The volume of ash within these plumes remains light and does not warrant an ashfall advisory at this time. Gulf of Papagayo: Moderate to at times fresh northeast winds will pulse across the Gulf each night through the end of the week. Elsewhere, the monsoon trough will exist from about 08N to 10N during the rest of the week, with gentle to moderate northeast winds north of the trough, and gentle to moderate southwest winds to the south of the trough. Seas north and south of the trough will be in the range of 5 to 7 ft in cross-equatorial SW swell through Tue, except for slightly higher seas of 6 to 8 ft between 118W and 120W. REMAINDER OF THE AREA... The pressure gradient between A 1025 mb high center analyzed near 30N132W and lower pressure near the ITCZ supports an area of fresh to strong NE winds over the waters from 09N to 15N and west of 131W. Altimeter data continue to show seas of 8 to 10 ft in this region, with seas 8 ft or greater extending as far north as 17N and as far south as 08N. The gradient between a 1009 mb low centered near 09N119W and the high pressure to its northwest and north is producing fresh winds in the NW semicircle of the low, with seas to 9 ft within 180 nm in the NW and N quadrants of the low and within 60 nm in the SE quadrant of the low. The low is forecast to track in a general westward direction through Tue before weakening to a trough Wed. Large-long period NW swell associated with a strong cold front located about 400 nm to the northwest of the discussion area will propagate southeastward through the northern and central waters through Wed, with seas rapidly building to the range of 12 to 15 ft in the far northwest section of the area by early Tue. The leading edge of the 8 ft seas is expected to reach near 106W by early on Thu. $$ Aguirre