000 AXPZ20 KNHC 271606 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Tue Nov 27 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... Low pressure of 1008 mb is presently embedded in the monsoon trough near 11N105W, moving northwad. It continues to produce disorganized shower and thunderstorm activity. Scattered moderate convection is within 90 nm of the center in the NE quadrant and 60 nm of the center in the NW quadrant. Environmental conditions are forecast to become conducive for some gradual development and a tropical depression could form during the next few days. The low pressure is forecast to continue to continue to move northward today, then turn northeastward toward southwestern Mexico on Wed. The low has a medium chance of becoming a tropical cyclone during the next 48 hours. Refer to the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOEP/ABNT20 KNHC for more information on this system. Gale Warning: A gale sarning remains in effect for the Gulf of Tehuantepec. The pressure gradient between strong high pressure in eastern Mexico and lower pressures south of Tehuantepec is supporting 30 to 40 kt northerly winds, as was clearly exhibited from an overnight ASCAT pass. Visible imagery shows a well depcited large arc cloud feature, that denotes the onset of the strong to gale force northerly winds, emanating well away from the Gulf, with its furthest southward extent approaching 10N. The longitudinal width of the arc reaches eastward to near 92W and westward to near 99W. Seas are in the range of 10 to 14 ft with these winds. The gale force winds are forecast to continue through early Wed, then rapidly diminish Wed and Wed night across the region. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from far northwestern Colombia to 09N79W to 08N94W to low pressure near 11N105W 1009 mb, to 09N112W to low pressure near 09N120W and to 08N125W, where latest scatterometer data indicates the ITCZ axis begins and continues to 07N134W and to beyond 08N140W. Scattered moderate isolated strong convection is within 120 nm south of the trough between 82W and 85W. Scattered moderate convection is within 180 nm south of the ITCZ between 101W and 104W and between 133W and 139W. Similar convection is within 60 nm of the ITCZ between 124W and 131w, and within 30 nm south of the trough between 90W and 94W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Moderate to fresh northerly winds are expected across the north and central Gulf of California today, with seas of 3 to 5 ft. Winds are expected to increase to 20 to 25 kt with seas of 5-7 ft across the northern Gulf Thu night and Fri as a cold front sweeps across the area. Wave model guidance indicates that large long-period NW swell associated with a cold front approaching 30N140W will reach the waters west of Baja California Norte beginning late tonight, and the southern tip of Baja California by late Wed night. Seas induced by the swell are expected to be in the range of 10 to 14 ft as they propagate across the waters north of about 20N and west of 115W by early Thu morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Enhanced infrared imagery from GOES-E continues to show a plume of volcanic ash originating from the Fuego volcano in southern Guatemala. The plume is tracking in a west-northwest direction, becoming diffuse in southwestern Mexico near the coast of the state of Chiapas. The anticipated volume of ash within this plume remains light and does not warrant an ashfall advisory at this time. Gulf of Papagayo: Fresh northeast winds will pulse across the Gulf each night through Sat. Elsewhere, the monsoon trough will meander between 08N and 10N during the rest of the week, with gentle to moderate winds on either side of the trough, with 5 to 7 ft seas expected. REMAINDER OF THE AREA... See Special Features Section above for the latest information on a low pressure system with potential for tropical development. The pressure gradient between a 1024 mb high centered near 29N131W and lower pressures near the ITCZ is resulting in fresh to strong northeast winds over the waters from 09N to 12N between 130W and 137W. This area of trades will shrink today, and its 8-10 ft seas will merge with the large NW swell event sweeping across the forecast waters during the next few days. Seas will rapidly build to 12 to 18 ft in northwest portion of the area this afternoon. The leading edge of the 8 ft seas is expected to reach the Revillagigedo Islands by early on Thu. $$ Aguirre