000 AXPZ20 KNHC 170958 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Jan 17 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 0600 UTC surface analysis and satellite imagery through 0930 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from 05N77W to southwest to 03N79W to low pressure near 01N83W 1010 mb. The ITCZ axis extends from 03N97W to 02N105W to 07N114W to 07N123W to 06N123W to beyond 06N140W. Scattered moderate convection is within 60 nm south of the axis between 110W and 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge extends from a 1025 mb high pressure center located at 28N127W southeastward to the Revillagigedo Islands situated about 265 miles southwest of the southern tip of the Baja California peninsula. Gentle to moderate winds prevail over the forecast waters off the coast of Baja California and over the Gulf of Tehuantepec. Light to gentle winds prevail over the waters off southwest Mexico and the Gulf of California. Seas are in the 5-7 ft range off the coast of Baja California, 2 ft or less over the Gulf of California, and 4-6 ft elsewhere. Global models are in good consensus in suggesting that a weakening cold front will move over the waters off Baja California Norte by Thursday, then become diffuse ahead of a stronger cold front that will quickly move across Baja California and the Gulf of California Friday through Saturday. The second front will be accompanied by fresh to strong winds and a large set of northwest swell forecast to bring very large seas in the range of 12-19 ft to the waters off Baja California Norte on Saturday, and seas of 8-13 ft to the waters off Baja California Sur at that same time as depicted in latest wavewatch model guidance. This could potentially bring hazardous conditions to mariners navigating through those waters. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Northwest winds will pulse to 20-25 kt late tonight into the early morning hours and again late Wednesday night across the Gulf of Papagayo before diminishing to moderate to fresh Thursday afternoon, and to moderate Thursday night into Friday and diminishing further to light to gentle variable winds Friday afternoon. Elsewhere light to gentle northeast to east winds will persist north of about 07N, and light to gentle south to southeast winds south of 07N. Seas are around the 3-4 ft range, except for slightly higher seas north of 07N with little change expected through Thursday. REMAINDER OF THE AREA... High pressure of 1024 mb centered north of the area near 30N134W extends a ridge southeast to near the Revillagigedo Islands. The pressure gradient between lower pressure in the vicinity of the ITCZ is supporting an area of fresh to strong trade winds from 11N to 15N west of 126W, with seas of 10-12 ft. Fresh trades are elsewhere from 06N to near 21N west of 113W with seas of 8-11 ft in a northwest to north swell. The fresh to strong trades will decrease in coverage during the next couple of days with model guidance depicting them to shift to west of 136W from 09N to 12N, and with seas of 9-10 ft. The fresh trades will be confined from 07N to 20N and west of 122W also at that time, with seas of 8-10 ft in mixed northeast and northwest swell. Looking ahead, the areal coverage of the fresh to strong trade winds and associated seas will decrease Thursday as the high pressure north of the area weakens ahead of an advancing cold front. Northwest swell with resultant seas of 8-12 ft will accompany the front as it moves eastward across the waters north of 25N Wednesday and Thursday while weakening, followed by a second front expected to sweep southeastward over the far northeast waters to the east of 130W late Thursday night into Friday. Wavewatch model guidance shows an extensive set of northwest swell that will propagate southeastward through the waters north of about 20N behind the second front. Seas with this swell event are expected to be in the 10-17 ft range, building to 15-20 ft in the far northern waters east of 130W late Friday into Saturday. A deep layer low situated over eastern Arizona extends a trough southwestward to 25N117W to 22N125W, then becomes rather narrow as it continues to 21N135W and west to beyond the area at 20N140W. A very active jet stream branch is rounding the base of the trough. Strong west to southwest with this jet are transporting abundant moisture from the deep tropics eastward and northeastward towards the far eastern portion of the area from 12N to 22N. Scattered showers and isolated thunderstorms are possible with this moisture plume. A considerable amount of mid to upper level cloudiness is being advected to the northeast with the jet stream winds. These clouds have moved inland over much of central Mexico as observed on satellite water vapor imagery. A weak surface trough is analyzed at 06Z along a position from 13N118W to 08N122W. The trough is under a very pronounced upper level diffluent flow pattern. Scattered showers and thunderstorms are noted within 150 nm west of the trough. The upper level trough will gradually translate eastward over the next couple of days as high pressure ridging builds eastward over the western and central portions of the area in the wake of the previously mentioned cold fronts. Mid to upper level cloudiness will remain over the eastern portion of the area on Thursday. The weak surface trough will move westward about 15-20 kt through the next 48 hours, then become diffuse in the trade wind flow. Another surface trough is forecast to develop in the vicinity of 111W- 114W and from 06N to 11N late on Thursday. $$ AGUIRRE