000 AXPZ20 KNHC 090907 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sat Dec 9 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 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning... Scatterometer data at 0400 UTC showed 40 kt N winds near the coast in the Gulf of Tehuantepec, and model guidance indicates winds will strengthen today as the pressure gradient across southern Mexico intensifies behind a strong cold front in the western Gulf of Mexico. These winds will further increase to storm force 50-55 kt tonight, persisting into late Sun with max seas building to 21-22 ft within the area of storm force winds. Gale force winds are likely to continue well into next week, producing a very large area of high seas well downstream from the source region. Gulf of Papagayo Gale Warning... Strong high pressure building north of the area behind a cold front entering the NW Caribbean later this morning will induce a strong gap wind event across the Gulf of Papagayo tonight into early Sun morning, when winds are forecast to reach minimal gale force. N to NE winds are expected with this event, reaching as far south as 07N88W by Sun. Seas are forecast to build to 10-11 ft downstream. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N85W to 08N94W to 09N113W. The ITCZ axis continues from 09N113W to 11N126W to beyond 09N140W. Scattered moderate isolated strong convection is noted over a large area north of the axis from 11N to 16N between 118W and 127W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: Please see Special Features section above. High pressure north of the area is supporting a tight pressure gradient over Baja California and northwest Mexico, with a scatterometer pass at 0400 UTC showing strong winds between 24N and 28N. NWP models suggest the winds will subside to 20 kt or less today, mainly S of 28N with max seas to 8 ft. Winds will remain 20-25 kt north of 30N tonight, then diminish Sun. N-NE winds funneling through the Baja California peninsula into the Pacific waters will diminish this morning, with seas subsiding below 8 ft off the coast of Baja California through tonight. Elsewhere gentle to moderate winds and 4-6 ft seas will persist through next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Please, see Special Features section above. Elsewhere, light to gentle N to NE winds are expected N of the monsoon trough, and mainly gentle to moderate S to SW winds are expected S of the trough. Seas are 4-7 ft in SW swell S of the monsoon trough. Large NW swell with wave heights of 8-10 ft from a strong Tehuantepec gap wind event mentioned above will spread across the offshore waters of Guatemala this weekend. Localized gap wind pulses of 20 to 25 kt are possible south of El Salvador and Guatemala, including the Gulf of Fonseca, starting tonight. REMAINDER OF THE AREA... Long period NW swell has spread across the forecast waters covering roughly the area west of a line from 30N122W to 23N110W to 19N110W to 03N140W. The long period NW swell will mix with shorter period NE swell originating from gap wind effects in Baja California this morning. A cold front will approach the area on Sun with S to SW winds increasing to 20 kt. The front will extend from 30N135W to 26N140W late Sun night, with seas of 12-16 ft building behind the front. $$ Mundell