000 AXPZ20 KNHC 080307 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 246 UTC Sun Jan 8 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 0230 UTC. ...SPECIAL FEATURES... A storm warning is in effect for the Gulf of Tehuantepec. Very strong high pressure is nosing southward over the western Gulf in of Mexico, forcing storm force winds over the Gulf of Tehuantepec tonight and through the day Sunday. Gale force winds surrounding the storm force wind area will expand tonight well to the south and southwest of the Isthmus of Tehuantepec. The high pressure center will shift eastward Sunday through Sunday night. This will loosen the pressure gradient over the Tehuantepec region and will help winds diminish to below storm force by Sunday night. Although winds will decrease below storm force, the gale force winds are expected to continue across the Tehuantepec region through late Tuesday. The high pressure ridge over the gulf will continue to shift eastward Wednesday and Thursday and set up SE to S return flow over the Gulf. This will bring this latest Tehuantepec gap wind event to an end by Thursday evening. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 06N86W to a 1011 mb low pressure near 06N94W to 06N101W. The ITCZ continues from 06N101W to 07N116W, then resumes west of a surface trough near 08N122W to a 1009 mb low pressure near 08N126W to beyond 09N140W. Isolated moderate convection is within 90 nm of the low pressure centers. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more details on the Gulf of Tehuantepec storm force gap wind event. Elsewhere, a high pressure ridge axis extends from southern California to 25N120W then southward along 120W to the west of the Baja California Peninsula. Gentle to moderate N to NE winds with seas in the 3-5 ft range are along the west coast of the Baja California peninsula. The pressure gradient between this ridge axis and a surface trough over Mexico is generating fresh to strong winds over the central and southern Gulf of California region. The pressure gradient will loosen slightly on Sunday as pressures rise over Mexico. This will bring winds below advisory criteria by Sunday evening. Elsewhere between Cabo Corrientes and the Tehuantepec region, light to gentle breezes prevail with seas in the 3 to 5 ft range through Sunday. Winds along the coast will increase to moderate Sunday night into Monday briefly before once again becoming light to gentle Monday night. These lighter winds will then prevail through the middle of next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The very strong high pressure building behind the cold front responsible for the Gulf of Tehuantepec storm event will cause strong northeast gap winds to develop across the Gulf Papagayo late tonight, then both the Gulf of Papagayo and Fonseca by Sunday. Winds are forecast to reach near gale force in the Papagayo area late Sunday night into Monday with seas building up to 12 ft. These winds will prevail through the middle of next week as the strong high gradually shifts eastward to the north of the region. In the Gulf of Panama, fresh nocturnal northerly flow is expected through Sunday night. Winds will further increase to 20-25 kt Sunday night through Tuesday as strong winds funnel from the SW Caribbean into the Gulf of Panama, as high pressure behind the cold front over the Caribbean waters tightens the pressure gradient. These gap wind events, along with the storm force wind event in the Gulf of Tehuantepec, will generate a large area of 8 ft seas or greater that will merge and eventually extend from Tehuantepec and Papagayo regions southward to near the equator and westward to near 118W Monday night. The area of large seas will shift westward and begin to decay on Tuesday and Wednesday. Elsewhere, light to moderate south to southwest winds will prevail south of the monsoon trough region, with seas 6 ft or less through the upcoming weekend. REMAINDER OF THE AREA... A pair of surface troughs extend over the northwest corner of the area of discussion, one from 30N132W to 26N135W, and the other from 30N136W to 24N140W. The combination of an upper trough to the northwest of these surface troughs and the surface troughs themselves support scattered moderate to strong convection within 120 nm east of the easternmost trough, with isolated moderate convection elsewhere north of 25N and west of 133W. Strong southwest winds are also within 240 nm east of the easternmost trough, and 120 nm to the east of the western trough. A strong cold front will move into the northwest waters later tonight into Sunday. This front will merge with these surface troughs and help to expand a large area of fresh to strong winds over much of the northwest and north central waters. Winds will peak near gale force east of the front early Sunday with seas building to near 11 ft. Elsewhere, gentle to moderate trades are forecast over most of the area to prevail under a weak pressure pattern. The only exception is a surface trough along 120W between 04N and 11N that is forecast by global models to intensify slightly the next couple of days. As a result, the pressure gradient between this trough and ridging to the northeast of the region will support fresh to strong easterly winds within about 120 nm east of the trough axis. $$ LATTO NATIONAL HURRICANE CENTER