000 AXPZ20 KNHC 181517 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1517 UTC Mon Dec 18 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough axis extends from the coast of western Colombia near 04N77W to 06N93W. The intertropical convergence zone axis extends from 06N93W to 09N110W to 10N130W to 10N140W. Scattered moderate and isolated strong convection is from 08N to 10N between 106W and 109W, and also from 11N to 15N between 114W and 118W. Scattered moderate convection is from 07N to 10N between 125W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... In the Gulf of California, a cold front extends from low pressure near the Arizona and Mexico border at 31N111W across Mexico to the central Gulf of California near 27N110W, then to across and offshore of the Baja California Peninsula. The low pressure will shift NE of the area today and drag the weakening front SE across the S portion of the Gulf before dissipating. Early observations showed fresh to strong NW-N flow in the far NW corner of the Gulf which should diminish this afternoon as conditions improve. Seas are 3-6 ft N of the front, and 1-3 ft S of the front. Moderate northerly winds are then expected across the Gulf through late Wed before the next front sweeps SSE into the area. Northerly winds will increase to strong to near Gale force behind this next front early Thu through Fri with seas building to 8 ft. These strong winds are also forecast to seep through Baja California passages into the open Pacific waters W of the peninsula. Active convection continues in a broad zone across the offshore waters of SW Mexico from the Manzanillo to Cabo Corrientes areas SW to near 16N110W. An upper level trough that supported the front that has moved through the Gulf of California lingers across the region, with upper level jet energy enhancing this convection. Active weather will continue across this region through Tue before shifting SW and well offshore. In the Gulf of Tehuantepec, offshore northerly winds will pulse to fresh to strong mainly during the overnight and early morning hours with seas occasionally building to 8 ft. Elsewhere across the offshore waters of Mexico, gentle to moderate mainly NW winds prevail. NW swell of 7-10 ft W of the Baja California Peninsula will continue to subside through tonight, with 4-6 ft seas elsewhere. A fresh pulse of NW swell will propagate into the waters off the coast of Baja California Norte Thu behind the next cold front, with seas building to near 9 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, winds will pulse to fresh to strong mainly during the night and early morning hours with seas occasionally building to 8 ft. In the Gulf of Panama, moderate to fresh winds will diminish later this morning, then will pulse again tonight into early Tue. Elsewhere, mainly gentle NE-E winds will prevail N of 09N, and moderate SW flow S of 09N. REMAINDER OF THE AREA... Northerly swell of 7-10 ft N of 20N continues to subside and will be less than 8 ft by early Wed. Mainly moderate winds prevail elsewhere over the forecast waters N of the ITCZ to 20N and W of 125W. High pressure across the NE Pacific will dominate the regional waters for the next few days with little change in wind speed magnitude. Looking ahead, the pressure gradient will increase N of 20N and W of 130W between the high and low pressure moving northward W of 140W. SE flow around the high will increase to fresh to strong with seas building to 7-9 ft Thu night. The low may then briefly cross to near 30N140W by late Fri night. The gradient may continue to tighten and if so, gale conditions may be possible in the NW corner with seas building to well over 12 ft. $$ Lewitsky