000 AXPZ20 KNHC 222141 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Thu Dec 22 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure ridging stretching southward along Sierra Madre Oriental mountains of Mexico combined with lower pressures south of the Tehuantepec area continues to result in a tight pressure gradient across the Isthmus of Tehuantepec. As a result, minimal gale force winds continue to blow across the Gulf of Tehuantepec. Model guidance indicates that the ridge will gradually slacken through Friday morning and into early Friday afternoon at which the gale force winds are forecast to drop to just below gale force. Expect fresh to strong northerly winds to then continue through Saturday morning, diminishing Saturday afternoon. Beyond the forecast period, northerly winds will then pulse to fresh to strong the next couple of nights this weekend, with another gale force wind event possible by Tuesday of next week. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 05N94W. The intertropical convergence zone axis continues from 05N94W to 07N106W to 08N122W, then resumes W of a trough at 09N127W to beyond 08N140W. Scattered moderate convection is from 08N to 10N between 110W and 115W. Scattered moderate convection is north of the ITCZ within 30 nm of 13N113W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Mainly light to moderate southerly flow will prevail across the northern half of the gulf, with light to moderate northerly flow across the southern half through Friday. A cold front approaching from the west will bring an increase in winds across the northern gulf by early Saturday with 20 to 30 kt winds possible. The cold front will be moving across northern Baja California and the Gulf of California, also including forecast zones PMZ009, PMZ011, and PMZ013 Saturday and Saturday night. Northwest winds of 20 to 25 kt and building seas of 9 to 13 ft in northwest swell are expected in the wake of the front. The highest of these seas are forecast to be confined to zone PMZ009, and the northwest section of zone PMZ011 late on Saturday. A trough extends from NW Mexico across the Gulf of California near to Baja California Sur and beyond to near 16N117W. Moisture associate with this system has diminished. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong northeast winds will continue to pulse during the overnight and early morning hours with the assistance of nocturnal drainage flow through Friday morning, then moderate to fresh winds are expected thereafter. Locally, these winds will produce seas up to 8 ft. Elsewhere across the region, winds will remain 20 kt or less, with seas below 8 ft through Saturday. Moderate Northerly winds are expected across the Gulf of Panama during the overnight and early morning hours. REMAINDER OF THE AREA... The combination of a 1027 mb high centered just north of the area near 31N140W and lower pressures in the vicinity of the ITCZ will continue to support a belt of fresh to strong trades from roughly 08N to 15N west of 125W. Seas of 8 to 10 ft area noted within the area of the trade winds based on altimeter passes. This high center is forecast to dissipate in about 24 hours. Long period northwest swell continues to impact much of the waters west of 115W with seas of 8 to 11 ft. Seas will slightly subside through Friday, but will build back across the northern waters on late Friday as a cold front reaches the northern forecast waters Friday night. Fresh to strong northerly winds and a new set of large northwest swell, with building seas up to about 14 ft along 30N, will follow the front. High pressure behind the front will shift southeastward to near 28N139W by Sunday morning. As this high pressure builds in, the aerial extent of the trades will increase again. The next cold front will drop into the northern waters Sunday night, while a parent surface low manages to rotate into the area by Monday night, however models differ on just how far south this low will track. $$ GR