000 AXPZ20 KNHC 020343 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sat Dec 02 2017 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 0200 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure north of the area supports a tight pressure gradient across the Isthmus of Tehuantepec and pulsing gale force northerly across the Gulf of Tehuantepec this evening. Wind are expected to increase slightly overnight through early Sat morning, peaking at 35-40 kt with 13 to 14 ft. The resultant plume of N to NE winds extending downstream of the gulf will produce an area of seas to 8 ft and greater extending 650 nm downstream SW of the gulf. Seas will subside to 8 to 10 ft Saturday afternoon through Sunday as winds gradually diminish to 20-30 kt. Winds will diminish to less than 20 kt with seas subsiding to less than 8 ft by early Monday. Another gale event is expected to develop mid-week as a strong cold front moves into the Gulf of Mexico and southern Mexico. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N73.5W TO 10N82W TO 07N107W, where it transitions to ITCZ, then continues on to 10N116W TO 11N129W to beyond 08N140W. Scattered moderate isolated strong convection is noted from 06N to 09N between 79W and 85W, and from 06N to 08.5N between 102W and 112W. Scattered moderate to strong convection is noted from 08.5N to 16.5N between 115W and 132W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... An upper level disturbance moving slowly across Baja California Norte this evening will continue eastward into northern Mexico Saturday, and likely produce scattered light rainshowers and isolated elevated thundershowers across the northern Gulf of California through Sat morning. Weak ridging over the region will support gentle to moderate northerly winds across the area into early next week. Long period NW swell propagating across the waters offshore of Baja California the past 2 days has reached to near 102W, and is producing 6 to 10 ft seas across the offshore waters of north and central portions of Baja California, and 5 to 9 ft seas from Baja California Sur to south of Manzanillo. This swell will reach the Revillagigedo Islands at 10 ft by early Sat, then slowly decay below 8 ft by late Mon. High pressure building in the wake of a cold front moving across the SW U.S. Sunday night through Monday night will induce strong NW winds through the entire length of the Gulf of California Monday and Tuesday. Looking ahead, the high pressure will build through mid week, possibly bringing winds to gale force to the northern Gulf of California with seas 8 to 12 ft. Please see Special Features section for details about the gale warning in the Gulf of Tehuantepec. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: A modest pressure gradient between a high over the far western Gulf of Mexico and lower pressure in the southwest Caribbean is producing fresh to occasionally strong offshore gap winds across the Papagayo region. Winds are being enhanced by diurnal drainage effects, and will peak near 25 kt during the late night and early morning hours. Seas downstream will build to 6-8 ft during the time of peak winds, diminishing slightly each afternoon and evening. Elsewhere, light to gentle N to NE winds and 4-5 ft seas are expected through Saturday north of the monsoon trough. Moderate S winds and 4-6 ft seas are forecast south of the trough axis. REMAINDER OF THE AREA... A large area of long period NW swell producing seas of 8-12 ft will continue to propagate across the region west of 110W. The swell will decay to less than 8 ft south of 20N through next week, but persist at 8 ft and greater north of 20N due to reinforcing NW swell entering the region. High pressure near 31N135W supports fresh winds north of 14N and west of 125W, and is enhancing fresh to strong trade winds between 10N and 20N west of 130W. Winds will diminish tonight as the ridge weakens. A mid level disturbance near 20N125W will move very slowly ENE through Sat, and will interact with low level ITCZ moisture to produce active convection to the E and SE of this feature through late Sat. A cold front NW of the area is expected to close off a surface low near 32N140W Sat morning as a short wave mid level trough deepens in the central Pacific. This low will deepen Sat night and drift SW, creating a tight pressure gradient and near gale force winds north of the low center, and just W of the far NW waters. This is expected to produce strong E winds sinking into the NW waters Sunday afternoon and evening, and maintain seas near 12 ft in NW swell. The low will continue to drift SW and late Sunday , with associated seas subsiding to 8-10 ft by early Mon. $$ Stripling