000 AXPZ20 KNHC 060948 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0945 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: Minimal gale force northerly winds will diminish just before sunrise this morning. Strong to near gale northerly winds will then continue through Fri evening with these conditions extending as far SW as 13N97W and maximum seas of 13 ft downstream of the gulf near 14.5N95.5W early this morning. The next gap event will begin on Sun morning with strong gale conditions developing on Sun evening and persist through wed night. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends W across Panama along 08.5N to the Pacific coast at the Panama and Costa Rica border to 06N95W, then turns NW to 10N113W with a N to S trough is analyzed from 05N118W to 13N117W. Scatterometer winds indicate an ITCZ develops at 10N120W and extends W-SW to 08N133W to beyond 09N140W. Scattered moderate isolated strong convection is observed within 120 nm either side of lines from 06N85W to 06N95W to 10N100W. Similar convection is observed N of the monsoon trough within 75 nm either side of a line from 12N102W to 16N112W. 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 southwesterly 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 central gulf waters on Fri night and Sat, and continue through Sun, with locally strong winds possible near 26N110W on Sun. Elsewhere: Fresh southerly flow is observed N of 28N ahead of surface low at 32N118W which is trailing a weak warm front SE over the extreme northern Baja Peninsula, and trailing a cold front SW that will move across the offshore waters W of the Baja Peninsula through Fri. Long-period NW swell, in the form of 7 to 9 ft seas, will reach 32N116.5W this evening, with these seas propagating S reaching the W shore of the southern Baja Peninsula early Sat, just as the seas begin to subside from the N, with these seas forecast less than 8 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... A thin volcanic ash plume, originating over interior Guatemala, is observed on satellite imagery spreading southwest across the Pacific coast of Guatemala and extreme SE Mexico, between 14N and 15N, but may not be sinking to near the surface. 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 couple of surface lows analyzed along 32N between 118W and 125W will merge and then move E and inland 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. $$ Nelson