000 AXPZ20 KNHC 121556 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1408 UTC Wed Oct 12 2016 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 FEATURES... A gale warning remains in effect for the Gulf of Tehuantepec. Early this morning, an scatterometer pass indicated several wind barbs of 30 kt, and winds to minimal gale force were possible with the aid of the nocturnal drainage flow. These winds are a result of fairly tight pressure gradient between high pressure over east central Mexico and linger lower pressure south of the area in the tropical eastern Pacific. Winds will diminish during the day to 20-30 kt, but another round of minimal gale force winds are possible in the Gulf of Tehuantepec late tonight into Thursday morning. Strong gap winds will pulse again Thursday night into Friday morning with marine guidance showing northerly winds of 20-30 kt. The overall pattern will slightly improve as high pressure north of the area weakens, and 20-25 kt gap winds are anticipated by Friday night into Saturday morning. ...TROPICAL WAVE... A tropical wave is along 89W N of 07N. Scattered moderate convection is noted ahead of the wave axis from 11N to 13N between 89W and 92W. The wave is well depicted in the moisture products and it is forecast to reach the Gulf of Tehuantepec region on Thursday. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N78W TO 09N85W to 08N94W to 1008 mb low pressure near 12N106W to 15N120W to 10N134W to beyond 08N140W. Scattered moderate to isolated strong convection within 90 nm S of trough E of 88W...and within 90 nm N of trough between 130W and 135W. Scattered moderate from 11N to 13N between 120W and 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge extends from 1021 mb high pressure centered north of the area near 32N130W to near the Revillagigedo Islands, supporting gentle to moderate northwest to north winds off the Baja coast with seas of 5-6 ft based on an altimeter pass. These winds will increase to 15 to 20 kt by late today as the ridge builds slightly eastward. The high pressure will weaken Thursday ahead of a frontal boundary moving into the northeast Pacific, allowing the winds to diminish. Looking ahead, long period northwest swell will push into the waters off Baja California Norte by Friday and Baja California Sur Friday night, with building seas of 8-10 ft by early Saturday morning. Winds to 25 kt with seas to 11 ft are possible off the northern portion of Baja California Norte, that includes forecast zone PMZ009,by late Saturday as well as the ridge builds eastward again. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate southwest winds persist south of the monsoon through...including the waters between Ecuador and the Galapagos Islands. Seas are 4 to 6 ft south of the monsoon trough largely associated with long period southwest swell. These marine conditions will change little over the next few days. REMAINDER OF THE AREA... Disorganized showers and thunderstorms are associated with a broad area of low pressure located near 12N106W. Some slow development of this system is possible during the next several days while the low moves west-northwestward at 15 to 20 mph away from the coast of Mexico. The most recent scatterometer data indicate an area of fresh to strong winds within 90 nm N semicircle of low center with seas to 9 ft. Currently, a cluster of moderate to strong convection is within about 120 nm NW quadrant of low center. Scattered moderate to isolated strong convection is noted elsewhere from 11N to 15N between 104W and 111W. A second low pressure is centered near 18N126W producing a few showers and thunderstorms. The low is about to reach cooler waters, and tropical cyclone formation is not expected while the system moves westward at 10 to 15 mph. Fresh to strong winds are within 210 nm to the north of the center due to the pressure gradient between the low and the ridge to the N. An earlier Ascat pass and a ship observation confirmed the presence of these winds. Seas of 8 to 10 ft are likely to persist as well, although this is in part due to incipient northwest swell already in the area. Elsewhere, a ridge dominates the north waters and is producing mainly gentle to moderate winds across the region outside of the low pressure mentioned above. A new round of long period northwest swell will move into the region late today and tonight, covering the area northwest of a line from 30N121W to 20N128W by early Friday morning, with 8 to 12 ft seas, highest to the northwest. The leading edge of this swell event will reach from Punta Eugenia Mexico to 06N140W by late Friday and from Los Cabos Mexico to the Equator at 136W by Saturday morning. $$ GR