000 AXPZ20 KNHC 040420 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Fri Jan 4 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES... ...GALE WARNING... A cold front moving across the western Gulf of Mexico tonight is expected to reach the eastern Bay of Campeche early Fri. Winds behind the front will funnel across the Gulf of Tehuantepec early Fri, increasing to gale force Fri late in the afternoon and continue through Sat morning, then briefly reach gale force again Sat evening and night. Wind will then diminish below gale force Sun morning and gradually diminish to less than 20 kt early Mon morning. For further details please see the High Seas Forecast issued by the National Weather Service under WMO/AWIPS headers FZPN03 KNHC/HSFEP2. ...GALE WARNING... A large area of disturbed weather associated with an upper trough and a broad area of surface low pressure is persisting across the tropical Pacific tonight between 114W and 136W. Satellite imagery the past several hours suggests that a surface low has developed near 11.5N122.5W. A strong pressure gradient to the north of this low is aiding in producing NE to E winds of 20 to 30 kt to the north of the low and extending to 19N. The low is forecast to move slowly northward over the next few days and could acquire some tropical or subtropical characteristics during that time. Regardless of tropical or subtropical cyclone development, the low is expected to produce gale-force winds Fri afternoon through Sat evening. There is a low chance for this system to become a tropical cyclone within the next two days. Please see the National Hurricane Center Tropical Weather Outlook under WMO/AWIPS headers ABPZ20 KNHC/TWOEP for further details. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 09N74W TO 02.5N79W TO 06N86W. The ITCZ extends from 05N93W TO 11N121.5W then resumes near 05N131W and continues to beyond 05.5N140W. Scattered to locally numerous moderate to strong convection is noted from 08N to 17N between 116W and 122W, and from 06N to 17N between 122W and 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... High pressure centered to the W of the area near 30N125W extends a ridge SE to near 17N107W. This pattern is producing moderate to locally fresh N to NE winds across the offshore waters of Baja California with seas of 4-7 ft in NW swell. Winds and seas will diminish slightly through Fri morning. A low pressure center currently just N of the ITCZ near 11.5N122.5W will track N-NE over the weekend, approaching the offshores waters of Baja California Sur early Sun. Variable gentle winds and increasing clouds and showers will shift into the area from the SW late Sat and Sun as this low approaches. NW swell associated with a weakening cold front and mixed swell associated with the low will start affecting the Baja offshore waters by Sat night. The low is expected to gradually merge with an approaching cold front Sun to produce fresh northerly winds across the offshore waters Sun afternoon and evening. Gulf of California: High pressure across the Great Basin region will support fresh to strong NW winds across the Gulf of California S of 29N tonight before winds diminish to around 15 kt Fri and 10-15 kt Fri night. Gulf of Tehuantepec: Fresh northerly gap winds will prevail across the near shore waters of the Gulf through early Fri morning. North winds will then increase to 20-30 kt by Fri morning as a cold front approaches the region from the north. Gales are expected to commence by Fri late in the afternoon, as discussed above in the special features section. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Strong NE to E winds are expected across and downstream of the Gulf of Papagayo through early next week. Moderate to fresh offshore gap winds are expected elsewhere from El Salvador to Panama through Fri. Elsewhere, gentle to moderate southerly winds are expected S of 08N. REMAINDER OF THE AREA... The pressure gradient between high pressure near 30N125W and lower pressure in the vicinity of the ITCZ and complex low pressure between 110W and 135W is maintaining a broad area of fresh to strong tradewinds N of the ITCZ to near 24N and W of 112W. This area of high pressure will remain in place N of the area through Fri to maintain this broad area of fresh to strong trades. A cold front approaching NW portions of the discussion area will nudge the weakening high pressure eastward on Sat and weaken the pressure gradient to the south. Long period NW swell is merging with this tradewind swell to produce seas of 8 to 11 ft over much of the area north of the ITCZ west of 120W. The cold front is expected to reach 30N140W early Fri and reach from 30N125W to 23N140W by Sat morning and from 30N117W to 20N130W by Sun morning. Large NW swell generated behind this front will move into area waters today, raising seas to 10-14 ft behind the front Sat morning and 10-13 ft by Sun morning. A deep layered upper low has become nearly stationary within the base of a mid/upper level trough near 15N136W this evening. This pattern is supporting a large area of active weather described above, and broad and complex low pressure at the surface. The low pressure is expected to merge into a primary low center by Fri afternoon. This low and associated moisture will move northward through Fri and then slowly weaken as it veers northeastward, affecting Baja California Sur and the adjacent waters with fresh SW winds and occasional showers through the weekend. Gale force winds are expected with this low. See special features section above for further details. $$ Stripling