000 AXPZ20 KNHC 061619 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Dec 06 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 1500 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: Minimal gale force northerly winds have diminished to around 30 kt this morning and the gale warning has ended as of 1200 UTC. Strong northerly winds will then continue through Fri evening across and downstream of the Gulf, with these conditions extending as far SW as 13.5N96.5W and maximum seas of 10 ft. The next gap event will begin on Sun morning with strong gale conditions developing Sun evening and persisting through Wed night. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 07.5N76.5W TO 09N84W TO 06N94W TO 10.5N120W. Overnight scatterometer winds indicated the ITCZ beginning near 10.5N121W and extends W-SW to beyond 08N140W. Widely scattered to scattered moderate to strong convection is observed within 60 nm N and 210 nm S of the trough between 87W and 97W, within 360 nm NE and 210 nm S of the trough between 102W and 119W, and within 120 nm N of the ITCZ W of 132W. The monsoon trough is forecast to transition to an ITCZ to the W of 90W during the upcoming weekend. ..DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec...See special features paragraph above. Gulf of California: A pre-frontal trough will sweep E across the northern gulf waters this morning, with fresh SW flow to the N of 30N ahead of the trough, and fresh NW flow developing briefly behind the trough. The associated cold front will pass through the northern gulf waters tonight into Fri, followed by fresh northerly flow that will spread SE across the north and central Gulf waters Fri evening through Sun evening. Winds are then expected to diminish Mon. Elsewhere: A weak 1016 mb high is centered across the waters of Baja California Sur near 22N117W, ahead of an approaching cold front, which extends from 30N117W TO 27N120W TO 18N132W. Fresh southerly flow is observed N of 26N within 120 nm E of the front, and moving into the coast of Baja California Norte. The front will move E and SE across the region, and reach from the N Gulf of California through central Baja by Fri morning, move into the southern Gulf and through Cabo San Lucas Sat morning, and then dissipate near Las Tres Marias Sat night. This front is supported by a deep layers low pressure system and upper trough located along the California coastal waters. A southern jet stream ahead of this upper trough is streaming across central Baja and into NW Mexico this morning, transporting dense high clouds and some elevated showers and thunderstorms that will shift SE through tonight. Long-period NW swell that has developed behind the front will move into the northern waters today to raise seas to 6-9 ft by this evening, and 7-10 ft across north and central waters on Fri as the swell also reaches Baja California Sur. High pressure will build across the Baja offshore waters Fri night and Sat behind the front to produce moderate Nly wind flow and peak seas of 8-10 ft across all Baja waters. Seas will then begin to subside from the N, becoming 5-7 ft by Sun evening. The next round of long-period NW swell, in the form of 7 to 9 ft seas, will reach 32N120W on Mon and propagate S across the waters W of the entire Baja Peninsula on Tue. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Narrow volcanic ash plumes, originating over interior Guatemala, has been observed on satellite imagery intermittently overnight spreading southwest across the Pacific coast of Guatemala and extreme SE Mexico, between 14N and 15N, but was likely not felt at the surface. Ash plumes has not been observed across this region in the past few hours. Gulf of Papagayo...Nocturnal pulses of fresh to locally strong NE winds, and 6 to 8 ft seas, are expected through Fri evening, and will extend as far W as 11N91W on Thu. Elsewhere: The monsoon trough will meander between 08N and 10N with light to gentle variable flow, and 3 to 6 ft seas, forecast N of the monsoon trough, and moderate southwesterly monsoonal flow, and 3 to 6 ft seas, forecast S of the monsoon trough. REMAINDER OF THE AREA... A pair of surface lows analyzed along 32N between 118W and 123W are embedded within the deep layered trough across the California coastal waters, and will merge and then move E and inland across the extreme northern Baja California Peninsula on Fri, while dragging a cold front E of 120W on Fri. Long period NW swell, in the form of 8 to 11 ft seas, is forecast to propagate E reaching along 110W on Sat. Another cold front will reach 32N137W on Fri accompanied by a moderate wind shift. A stronger cold front will reach 32N140W on Sat evening accompanied by a fresh wind shift and large post- frontal NW swell. $$ Stripling