000 AXPZ20 KNHC 210246 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec: A gale warning is in effect for the Gulf of Tehuantepec. A strong Gulf of Tehuantepec gap wind event commenced Sunday night due to a cold front that crossed the Gulf of Mexico. Cooler, drier air behind the front has been moving across the isthmus of Tehuantepec into the Gulf of Tehuantepec. While no marine observations have been available in the Gulf of Tehuantepec this evening, the Salina Cruz station in Mexico was reporting N 30 kt wind, consistent with gale conditions over the water. The event is gradually weakening and peak winds currently are around 40 kt with largest wave heights of around 18 ft. Winds should very gradually diminish as continuous cold air advection over the western Gulf is likely to reinforce the Tehuantepec event through Friday. Gale conditions should likely diminish for good by late Saturday as the surface wind switch to southerly over the western Gulf of Mexico. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N84W to 06N91W. The Intertropical Convergence Zone axis extends from 06N91W to 10N116W, then resumes at 12N122W to beyond 07N140W. Scattered moderate isolated strong convection is within 60 nm of the ITCZ axis between 122W and 127W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: At 0000 UTC, ship KAQP reported 25 kt NW winds in the central Gulf of California. No wave height measurements have been available recently, unfortunately. These winds are the result of a moderate pressure gradient between a 1035 mb high over the Four Corners area and troughing along the southern Gulf of California. These conditions should diminish to below 25 kt by Wednesday morning as the high weakens and shifts eastward. A strong upper-level cutoff low has induced a surface trough from 27N122W to 21N117W to 16N118W. Scattered moderate and isolated strong convection exists within 120 nm east of the trough from 15N to 20N as well as from 17N to 22N between 110W and 113W. No wind or wave observations have been available near this feature, but it is likely that E to SE winds of 20 to 25 kt are likely occurring on the east side of the trough along with seas of 8 to 10 ft in mixed E wind waves and NW swell. These conditions should diminish early on Thursday. On Saturday, southerly winds ahead of a cold front may reach a strong breeze in the northern Gulf of California. The cold front will be moving across forecast zones PMZ009, PMZ011, and PMZ013 late Saturday and Sunday. At this point, the front does not appear to be very strong and is not likely to produce gale force winds. However, the NW swell associated with the cold front could produce seas 12-15 ft on Saturday and Sunday. It does not appear that this front will cause significant winds/seas within the Gulf of California. 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 morning, 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 the Gulf of Tehuantepec gap wind event to provide a large area of 8 to 12 ft seas downstream of the gap regions. These gap winds will diminish below 25 kt by late Saturday. Elsewhere across the region, winds will remain 20 kt or less, with seas below 8 ft through Sunday night. REMAINDER OF THE AREA... A 1030 mb high centered north of the area near 34N139W along with surface pressures near 1010 mb along the ITCZ support a broad area of fresh to strong trades from roughly 07N to 22N west of 130W. Seas of 8 to 11 ft in mixed wind waves and NW swell cover the majority of the waters north of the ITCZ west of 120W. The high center is forecast to weakening over the next few days. As a result, the aerial coverage of fresh to strong winds will decrease by Wednesday and remain limited through Sunday. A cold front should drop south into the northern waters Friday night with a brief surge of fresh to near gale northerly winds possible behind it north of 28N. Large northwest swells, building seas up to about 15 ft along 30N, will arrive behind the front on Saturday. $$ CWL