000 AXPZ20 KNHC 171453 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1232 UTC Thu Jan 17 2019 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 1445 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from 07N77W to 04N85W to 03N92W. The ITCZ continues from 03N92W to 05N110W. It resumes from 05N115W to beyond 07N140W. Scattered moderate isolated strong convection is noted from 05N to 08N between 105W and 110W. Elsewhere scattered moderate isolated strong convection is noted from 07N to 16N between 104W and 115W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Strong to near-gale force winds prevail over the Gulf of Tehuantepec, with seas in the 8 to 10 ft range. Winds will pulse again to near gale force tonight. Winds will then diminish Friday as the pressure gradient weakens across the region. Fairly tranquil conditions will persist across the Gulf of Tehuantepec and downstream late Fri through late Sat. The pattern will change abruptly Sat night, as a the leading edge of a strong cold front moves through southern Mexico, across the isthmus of Tehuantepec and into the adjacent waters of the Gulf of Tehuantepec. As high pressure builds behind the front over east central Mexico, and the bulk of the cold air reaches the southern Gulf of Mexico, the initial gale force winds will intensify to a strong gale into Sun morning, possibly reaching minimal storm force. Seas will build accordingly, reaching as high as 24 ft by midday Sun. Meanwhile, a large plume of 25 to 35 kt winds and seas in excess of 12 ft will push as far as 420 nm to the south-southwest downstream of the Gulf of Tehuantepec. Strong gales will likely persist into Mon. Marine interests transiting through the Gulf of Tehuantepec Sun into early next week should be aware of this upcoming gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Elsewhere over the offshore waters outside of Tehuantepec... light to gentle breezes prevail across the region north of 25N, with gentle to moderate breezes elsewhere. NW swell of 8 to 9 ft prevails over open waters beyond 120 nm north of Cabo Corrientes. A weak cold front will move into into northern Baja California Norte this evening. While the front will dissipate as it moves across Baja California and the Gulf of California through Fri, it will be accompanied by a new set of long- period NW swell of 12 to 16 ft across the waters off Baja California. This swell will bring dangerous surf and large breaking waves across Baja California Norte Thu night through Fri. High pressure building behind the front will support fresh to strong NW winds north of Cabo San Lucas late Fri into Sat. Over the Gulf of California, high pressure building over the Great Basin north of the area will support fresh to strong NW winds extending the length of the Gulf from Fri night through Sat. The strength, fetch and duration of the winds support wave heights to 8 ft in the southern Gulf of California by Sat night. Winds and seas will diminish by Sun as the high pressure weakens and shifts east. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The pressure gradient between high pressure north of the area and the equatorial trough will maintain strong gap winds across Papagayo and Panama through early Sat. Over Papagayo, fresh to strong gap winds persist as far as 300 nm to the W-SW of the Gulf, with winds pulsing to near- gale force during the overnight and early morning hours. Seas will build to 8 to 10 ft. Over Panama, fresh to strong northerly gap winds will impact mainly the western Gulf of Panama extending into the waters south of the Azuero peninsula through the end of the week. Gap winds will diminish Sat and Sat night as high pressure north of the region shifts eastward ahead of a cold front. This will loosen the pressure gradient across the area. New high pressure will build in the wake of the front, supporting another round of even stronger gap winds through the Gulfs of Papagayo and Panama. Winds to gale force are possible through the Gulf of Papagayo Mon. REMAINDER OF THE AREA... Low pres of 1010 mb is centered near 07N113W, moving west at 10 to 15 kt. Fresh to strong winds prevail within 90 nm in the northern semicircle of the low pressure, with seas as high as 13 ft in the area of strong winds north of the low pressure. The low will weaken through today, and open into a trough tonight as it reaches 115W. The trough will weaken further as it continues westward along the ITCZ over the next several days. Farther northwest, a cold front reaching from 30N129W to 28N140W will weaken through today as it continues to move eastward across the waters north of 28N. The front has ushered in a new set of NW swell. Seas of 12 to 23 ft prevails NW of a line from 30N126W to 22N140W. Seas over the area associated to this swell have peaked and will slowly subside as the swell propagates SE. Elsewhere, seas in excess of 8 ft cover much of the forecast waters west of 105W. A ridge will build across the waters north of 25N in the wake of the front. This will result in a tightened pressure gradient, and strengthening winds over the tradewind belt north of the ITCZ. The ridge will weaken into Sun, allowing winds and seas to decrease across the tropics. Seas of 8 to 9 ft will persist Sun into next week south of 20N and west of 135W in a mix of NW swell and remaining windwaves from local trade winds. $$ AL