000 AXPZ20 KNHC 211559 RRA TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Dec 21 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 1545 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec: A gale warning remains in effect as a very tight pressure gradient continues between A 1026 mb high pressure located over eastern Mexico near 23N98W and relatively lower pressure across southeastern Mexico. In addition, a stationary front remains to the north of the area over the southwest Gulf of Mexico with cooler and drier air continuing to be funneled through the Chivela Pass southward. An Ascat pass from last night highlighted northerly winds of 30 to 40 kt winds across the Gulf of Tehuantepec, and seas are forecast to be 12 to 18 ft across the area. Winds are expected to only gradually diminish through the next couple of days as continuous cold air advection over the western Gulf is likely to reinforce the Tehuantepec event through Friday. Gale conditions should likely diminish Saturday as the surface winds gentle to moderate east to southeast over the western Gulf of Mexico. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 06N91W to 05N98W. Scatterometer data indicates that the intertropical convergence zone axis extends from 05N98W to 07N108W to 08N114W to 11N118W, where it is dissected by a surface trough that extends from 14N120W to 08N126W, then resumes from 08N130W to 06N140W. Scattered moderate convection is within 60 nm of axis between 105W and 107W, and also between 109W and 111W and within 60 nm south of the axis between 117W and 118W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: The pressure gradient across the area is continuing to weaken, and the earlier fresh to strong northwest to north winds over the central portion of the gulf have diminished to a moderate to fresh breeze. These winds will shift to the southern portion of the gulf on Thursday, with mostly light to gentle variable winds elsewhere except for moderate northwest winds over the central gulf. Conditions are expected to change little on Friday. A 1014 mb surface low at 24N123W is associated with a strong upper-level cutoff elongated north to south low observed near 27N123W. A trough extend northeast from the low to near 27N123W, and south from the low to near 21N124W. A surface trough is located east of the low along a position from 27N118W to 22N117W to near 16N118W. An upper-level diffluent pattern to the east of the low is aiding a swath of scattered moderate isolated strong within 150 nm east of the the second trough from 16N to 24N. An area of 8 to 9 ft combined seas in a northwest swell is east of the low from 12N to 24N between 114W and 119W. These seas are forecast to subside to less than 8 ft tonight into Thursday as the low lifts to the north and northeast while weakening further. On Saturday, southerly winds ahead of a cold front may reach a fresh to near gale force breeze in the northern Gulf of California. The cold front will be moving across forecast zones PMZ009, PMZ011, and PMZ013 Saturday and Saturday night. The northwest swell associated with the cold front could produce seas of 9 to 13 ft with the highest of these seas expected to be confined to zone PMZ009, and the northwest section of zone PMZ011 late on Saturday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong northeast winds are expected to pulse in and downstream of the Gulf of Papagayo to near 90W during the overnight and early morning hours through Saturday night, with the assistance of the nocturnal drainage flow. Locally, these winds will produce up to 8 ft seas. The fresh northeast swells will merge with a Gulf of Tehuantepec gap wind event to provide a large area of 8 to 12 ft seas downstream of the gap regions. Elsewhere across the region, winds will remain 20 kt or less, with seas below 8 ft through Sunday night. REMAINDER OF THE AREA... The combination of a 1030 mb high centered north of the area near 33N139W along lower pressures near the ITCZ region will support a broad area of fresh to strong trades from roughly 07N to 21N west of 133W. Seas of 8 to 11 ft in mixed wind waves and northwest swell cover the majority of the waters north of the ITCZ west of about 116W. The high center is forecast to weaken through Saturday as it moves to the southwest. As a result, the aerial coverage of fresh to strong winds will decrease. Global models suggest that a cold front will sweep through the northern waters Friday night with a brief surge of fresh to near gale northerly winds possible behind it north of 28N. A set of large northwest swell will building seas up to about 14 ft along 30N, will arrive behind the front by early Saturday. High pressure behind the front will shift southeastward to near 31N134W by Saturday night. $$ Aguirre