000 AXPZ20 KNHC 272118 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2117 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURE... Gale Warning: A gale warning 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 morning ASCAT pass. Visible satellite imagery depicts a large arc cloud feature located about 400 nm SSW of the Gulf while emanating well away from it. It denotes the onset of the strong to gale force northerly winds. The furthest extent of the arc cloud is approaching 10N. The longitudinal width of the arc cloud reaches eastward to near 92W and westward to near 99W. Seas are in the range of 10 to 14 ft with the gale force winds. The leading edge of the 8 ft seas will reach to near 08N between 94W and 102W. The gale force winds are forecast to continue through early Wed, then rapidly diminish Wed and Wed night across the region as high pressure over eastern Mexico quickly moves eastward and weakens. Seas in the Gulf region will subside to less than 8 ft late Wed night. Elsewhere, low pressure of 1008 mb is presently embedded in the monsoon trough near 12N106W moving N at 10 kt. It continues to produce disorganized shower and thunderstorm activity. Scattered moderate convection is within 240 nm of the center in the NE quadrant. An arc cloud is evident approaching from the east, originating out of the Gulf of Tehunatepec. 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from far northwestern Colombia to 07N93W to low pressure near 12N106W 1008 mb, to another low pressure center near 09N120W to low pressure near 09N120W and to 07N125W, where latest scatterometer data indicates the ITCZ axis begins and continues to beyond 08N140W. Scattered moderate from 05N to 07N east of 85W. Scattered moderate isolated strong convection is within 90 nm either side of the trough and ITCZ west of 120W. ...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, with seas of 3 to 5 ft. Winds are expected to increase to 20 to 25 kt with seas of 5 to 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... Gulf of Papagayo: Fresh northeast winds will pulse across the Gulf each night through Sat. Elsewhere, the monsoon trough will exist between 08N and 11N 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...Updated 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 27N132W and lower pressures near the ITCZ is resulting in fresh to strong northeast winds over the waters from 09N to 12N west of 130W. This area of trades will continue to shrink through the evening, and its 8 to 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 NW swell over the northwest portion of the area this evening. A cold front associated with the NW swell will rapidly reach from near 32N137W to 29N140W by early Thu and weaken as it reaches from 32N125W to 26N131W to near 24N140W by early Fri. The leading edge of the 8 ft seas is expected to reach the Revillagigedo Islands by early on Thu. $$ Christensen/Aguirre