000 AXPZ20 KNHC 120352 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Mon Nov 12 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 0000 UTC surface analysis and satellite imagery through 0345 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: Presently strong north to northeast winds are ongoing across the Gulf of Tehuantepec, with seas of 8 to 10 ft. These conditions will diminish by early Mon. A strong cold front will move across the Gulf of Mexico Tue through followed by an area of strong high pressure. Northerly flow with the high pressure will significantly increase as the resultant tight pressure gradient between the high pressure and front tightens. This will increase the northerly winds through the Isthmus of Tehuantepec that will usher in a cold air mass over already present very warm sea surface temperatures of 29.5 to 30.0 Celsius. This set up is classic for the onset of strong to near gale force north to northeast winds to occur across the Gulf of Tehuantepec beginning early Tue. These winds are forecast to increase to 30 to 40 kt by early Tue afternoon, with seas of 9 to 14 ft. Model guidance suggests that these winds then quickly increase to 40 to 45 kt by early Tue afternoon as strong high pressure builds over northeastern Mexico and surges southward along the Sierra Madre Oriental mountains. The pressure gradient will tighten further across the Isthmus of Tehunatepec allowing for the strong gale force winds to reach minimal storm force (48 to 50 kt) by early on Tue evening. Seas downstream of the Gulf of Tehuantepec are expected to build up to a maximum of around 22 ft by Tue night. 925 mb wind and instability guidance from the regional NAM model indicates that the storm force winds should continue into Thu before diminishing to gale force winds that the guidance indicates are likely to last through late Fri night. Gale Warning along and near the west coast of Baja Peninsula: Strong high pressure building across the southwestern United States and northern Mexico will bring strong to near gale force northerly winds over the Gulf of California. These winds will funnel through mountain passages across north-central Baja California and bring gale force northeast winds within 60 nm of the west coast of Baja California between about 28N to 30N beginning Mon evening and continuing through Tue morning. Seas of 8 to 10 ft and northeast winds of 20 to 30 kt can be expected over the waters within about 180 nm to the southwest of the gale force winds Mon night through Tue evening. ...TROPICAL WAVES... The axis of a tropical wave extends from 09N115W to 17N115W, moving westward at 10 to 15 kt. The significant convection earlier observed has diminished to isolated showers and thunderstorms within 60 nm either side of the wave axis from 09N to 14N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N75W to 09N87W to 08N100W to a 1010 mb low centered near 09N115W. The ITCZ extends from 09N115W to 10N126W, where it is interrupted by trough that extends from 08N135W to 10N130W to 14N128W. The ITCZ continues resumes just west of the area near 08N140W. Scattered moderate isolated strong convection is within 120 nm south and 60 nm north of the monsoon trough between 111W and 114W. In association with the trough that extends from 08N135W to 10N130W to 14N128W, scattered moderate isolated strong is within 360 nm SE of the trough between 130W and 135W, and within 60 nm of the trough between 129W and 132W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on upcoming Gulf of Tehuantepec storm event and on a gale event near the west coast of Baja California. Gulf of California: Strong high pressure will build again N the area tonight and Mon, resulting in fresh to near gale force winds N of 30N beginning late this evening. These winds will spread southward across the entire length of the Gulf of California and across the waters between Las Marias Islands and Los Cabos by Mon evening. Seas are forecast to build to 8 to 10 ft before starting to subside Tue morning as the ridge slightly shifts eastward. Outside the gale force northeast winds and elsewhere winds of 20 to 30 kt expected to the west and southwest of the Baja California Peninsula, mainly light to gentle northeast winds and seas of 3 to 5 ft will continue south to near 17N through late tonight, then increase to gentle to moderate winds with seas of 4 to 6 ft from early Mon through Wed afternoon, at which time the winds diminish back to light to gentle intensity. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to occasionally strong winds will pulse over the Gulf of Papagayo through Mon morning, with moderate to fresh winds thereafter. Winds will increase back to fresh to strong by Wed night as a tight pressure gradient develops over northern Central America behind a strong cold front moving into the NW Caribbean. Seas are forecast to build to 9 ft by early Thu morning. A strong Tehunatepec gap wind event W of the area is forecast to spread strong to near gale force winds and building seas of 12 to 20 ft into the far SW portion of the offshore waters of Guatemala and El Salvador, particularly W of 93W, Tue night through Wed. Otherwise, light to gentle winds are forecast N of the monsoon trough, with gentle to moderate SW winds S of the monsoon trough through the next several days. Cross equatorial long period SW swell will keep seas in the 6 to 7 ft range between Ecuador and the Galapagos Islands as far north as 06N through Wed. REMAINDER OF THE AREA... High pressure centered west of California has an axis that extends SE across the forecast waters to near 22N113W supporting mainly gentle to moderate winds N of the ITCZ. The pressure gradient is forecast to tighten Mon night into Tue morning resulting in fresh to locally strong trades just N of the ITCZ. Seas of 8 to 9 ft will be associated with these winds covering roughly the waters from 10N to 17N W of 120W by Tue. A cold front will attempt to approach 30N140W the next few days, but will stall and weaken just to the northwest of the area. A set of northwest swell associated with this front is forecast to cross 30N140W by early Wed, with seas of 8 to 10 ft covering much of the waters north of 10N W of 130W by early Thu. Cross equatorial swell of 7 to 9 ft will spread N to 07N between 100W and 120W Mon through Tue night. $$ Aguirre