000 AXPZ20 KNHC 222200 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2029 UTC Fri Dec 22 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 1800 UTC surface analysis and satellite imagery through 2030 UTC. ..SPECIAL FEATURE... ...Eastern Pacific Ocean Gale-Force Winds... A 1009 mb extratropical low centered west of our area near 23.5N146W is expected to intensify and head NE during the next 24 hours, then weaken quickly and slow down as it loses upper- level support. Satellite-derived wind data from around 20 UTC this afternoon indicated that fresh to strong winds were already occurring over the forecast waters N of 17N and W of 136W. This system will pass very close to the NW corner of the discussion area and produce a brief period of gales from around 12 UTC Sat to 00 UTC Sun. By Sunday evening, winds associated with the low will drop below 20 kt. Combined SE wind waves and NW swell should produce peak seas around 15 feet near 30N140W on Saturday. A lingering NW swell of about 8 to 11 ft will slowly move southeastward and decay through Tuesday. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 06N77W to 05N79W to 07N88W to 06N97W to 07N104W. The ITCZ continues from 07N104W to 09N114W to 08N118W to beyond 10N140W. Scattered moderate convection is present from 06N to 10N between 135W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Satellite-derived winds and surface observations indicate fresh to strong NW to N winds are continuing throughout the entire Gulf. Seas in the southern Gulf are as high as 8 ft. Gaps in the Baja California mountains are allowing some strong NE winds to bleed through to the Pacific coast. These winds will gradually weaken by Sunday morning as the high pressure over the SW United States slowly weakens. Gulf of Tehuantepec: A strong cold front entering the Gulf of Mexico on Saturday will induce a gap wind event in the Gulf of Tehuantepec starting Saturday evening. Gale conditions are expected Monday morning through Tuesday morning. The global models have come into better agreement on the timing and magnitude of this event. Seas in the Gulf should peak around 13 ft on Monday morning, then remain 8 ft or greater through at least Wednesday morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to occasionally strong gap winds in the Gulf of Papagayo will continue through Saturday night. Winds will increase slightly Sunday morning and continue through at least Wednesday morning. Seas will peak around 8 ft. NE swell to 9 ft will clip the western offshore waters of Guatemala Monday and Tuesday due to the Gulf of Tehuantepec gap wind event. Otherwise, gentle to moderate winds and seas of 5 to 7 ft can be expected the next several days. REMAINDER OF THE AREA... See the Special Feature section above for details about the Gale Force Wind event expected on Saturday for the waters near 30N140W. Scattered moderate convection is occurring well ahead of this system over our waters N of 22N and W of 137W. Elsewhere, moderate to fresh winds prevail with seas running between 6 and 8 ft. Early next week NW swell generated by the special features low will slowly propagate SE into the discussion waters and cover an area W of a line from 30N125W to 18N125W to 10N138W by early Tuesday. $$ CAM