000 AXPZ20 KNHC 300316 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 052 UTC Fri Dec 30 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 Gale Warning...The pressure gradient between high pressure over eastern Mexico and lower pressure within the monsoon trough over the eastern north Pacific is supporting gale force winds over the Gulf of Tehuantepec. Gale force winds will increase slightly and continue Friday and Friday night as high pressure builds behind a cold front moving across the Gulf of Mexico. The area of high pressure will then shift rapidly over the southwestern Atlantic waters Saturday morning, which will cause the winds over the Gulf of Mexico to veer. This will decrease winds funneling into the Gulf of Tehuantepec and bring an end to the latest gale force gap wind event. Please see the latest National Hurricane Center High Seas Forecast product under AWIPS/WMO headers MIAHSFEP2/FZPN03 KNHC for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 04N77W to 04N80W to 10N84W to 05N92W to 05N95W. The ITCZ continues from 05N95W to 07N114W to 07N120W to 10N137W to beyond 10N140W. Scattered moderate and isolated strong convection is present from 01N to 07N between 76W and 78W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features section for details on the continuing Gulf of Tehuantepec gale-force gap wind event. The pressure gradient between the high pressure ridge west of the Baja California peninsula and a surface trough over western Mexico is supporting fresh to strong winds between the southern tip of Baja California and Cabo Corrientes. The trough will weaken tonight. This will relax the pressure gradient and allow wind speeds to decrease to 20 kt or less on Friday morning. A surface trough will arrive from the SW over the waters adjacent to the coast of Baja California Norte on Friday and Friday night. This will strengthen winds slightly and cause seas to build to between 8 and 9 ft within this area. The trough will shift east of the area Saturday and allow seas to subside below 8 ft. The next cold front will usher in a set of NW swell Saturday night and Sunday. Seas will build to near 10 ft in zone PMZ011 off the coast of Baja California Sunday. The swell will begin to subside on Sunday afternoon and allow seas to fall below 8 ft by Monday afternoon. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong winds will pulse at night over the Gulf of Papagayo through Saturday, then subside. Peak winds will occur during the overnight hours as the gap winds are enhanced by nocturnally induced drainage flow. Winds will decrease to 20 kt during the late afternoon and early evening hours. Elsewhere, winds will remain 20 kt or less, with seas below 8 ft through the end of the week. REMAINDER OF THE AREA... A weakening surface trough extends from 30N127W TO 24N130W. A weakening high pressure ridge is located north of the area. The pressure gradient between these features has loosened enough to allow winds to decrease below 20 kt. Lingering NW swell are propagating through the northern waters. Seas associated with these swell will subside below 8 ft Friday. Trades north of the ITCZ have also diminished to 20 kt or less. Lingering mixed NW and NE swell prevail from 10N to 17N W of 131W with seas in the 8-9 ft range. Seas over this area will also subside below 8 ft Friday. Trades north of the ITCZ are expected to remain below 20 kt during the next several days, but will remain just strong enough to cause seas north of the ITCZ to rebuild to between 8 and 9 ft in mixed NE wind waves and NW swell Friday through Monday afternoon. The extent of this area will be greatest on Saturday morning, when it will stretch from 06N to 14N between 95W and 127W. Another set of NW swell generated to the NW of a frontal boundary that is stalling northwest of the discussion area are beginning to enter the northwest waters. Seas associated with these swell will peak near 10 ft late Friday afternoon, then subside below 8 ft by Saturday evening. $$ cam