000 AXPZ20 KNHC 121003 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Dec 12 2019 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 0900 UTC. ...SPECIAL FEATURES... Gale force northerly winds continue tonight across the Gulf of Tehuantepec,behind a stationary front across the western Gulf of Mexico. Recent scatterometer data confirmed winds to 40 kt across Tehuantepec and extended SSW to near 13.5N96W. These gale force winds have peaked earlier this evening near 45 kt, with seas around 17 ft. Gale force winds will gradually diminish tonight through Thu, and are expected to taper off to strong then fresh Thu night through Fri. Gap winds will be below 20 kt by Sat morning. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09.5N75W to 06N91.5W to 10N106W 08.5N111W. The ITCZ then continues from 08.5N111W to low pres 1010 mb near 09.5N121W to 06.5N124W to beyond 06.5N140W. Satellite imagery and derived lightning data shows widely scattered moderate convection 03N to 10N between 77.5W and 85W, and scattered moderate isolated strong convection from 07N to 13.5N between 106W and 122W. Scattered light to moderate convection is noted from 06.5N to 09N between 129W and 139W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 1027 mb high pressure centered near 30N131W is maintaining moderate northerly flow off the coast of Baja California, depicted well in recent scatterometer data and ship observations. The scatterometer data also showed fresh to strong NW winds across the Gulf of California between 25N and 28N between the high pressure to the west and resident troughing over northwest Mexico. Recent altimeter data suggest seas continuing at 4 to 6 ft seas off the coast of Baja California and 3 to 5 ft seas in the central and southern Gulf of California. The high pressure will persist west of the area through Fri, supporting moderate to occasionally fresh NW winds off Baja California. New long period NW swell in excess of 8 ft will reach the waters around Guadalupe Island and the northern coast of Baja California Norte by Thu night, reaching the Revillagigedo Islands by late Sat. Looking ahead, a trough or weak front will move into the waters off northern Baja California Norte by late Fri into Sat, supporting fresh to strong NW winds in that area, but allowing winds to diminish over the Gulf of California. Seas may reach 13 ft in NW swell over open waters off Baja California. The front or trough will weaken as it moves southward through Sun, but high pressure in the wake of this boundary will support another round of fresh to possibly strong northerly flow over the Gulf of California Mon and Tue. Farther south, gentle to moderate winds and 3 to 5 ft seas will persist off the southern Mexico coast between Tehuantepec and Cabo Corrientes into Fri, increasing slightly mainly off the area around Cabo Corrientes late Fri and Sat as the pressure gradient tightens. Large N to NE wind swell will propagate southward and away from Tehuantepec through late Thu, even as winds diminish there. This will keep offshore seas at 6 to 9 ft across the far offshore waters south of Acapulco to Puerto Angel through Fri morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong NE to E winds will pulse over the Gulf of Papagayo tonight with seas peaking near 7 ft, then moderate to fresh winds are expected for the remainder of the forecast period. Elsewhere, gentle to moderate S to SW monsoon flow will persist across the offshore waters of Costa Rica, Panama, Colombia, and Ecuador through Sat night, while moderate NW to N flow prevails across the Gulf of Panama. REMAINDER OF THE AREA... A 1027 mb high pressure center located near 30N131W is supporting fresh to strong tradewinds across the waters south of 25N and west of 120W. Recent altimeter data showed seas of 8 to 11 ft in the area of fresh trades. The high will move slightly southwest through Thu night and act to increase the pressure gradient to its south, and expand the area of strong tradewinds to south of 26N and west of 120W. A cold front will approach 30N140W and stall on Thu. Large NW swell generated by gales force winds behind the front are spreading out ahead of front. Seas will build across the region, particularly where the longer period NW swell mixes with the shorter period easterly trade wind swell. Seas will eventually peak between 12 and 14 ft Thu night and Fri morning in this area. A weak surface low heading westward along will further tighten the pressure gradient just north of the ITCZ west of 130W Fri through Sat. $$ Stripling