000 AXPZ20 KNHC 310830 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Dec 31 2020 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 0830 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N79W to 10N85W to 07N90W. The ITCZ continues from 07N90W to 05N100W and to 07N125W to 07N135W to 06N140W. Scattered moderate convection is observed from 06N to 08N between 130W and 135W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sharp mid to upper level trough that has been moving eastward over the region the past couple of days is now becoming a cut off low over north central Mexico. Associated deep low pressure at the surface over north central Mexico along with relatively higher pressure north of the area in the Great Basin and over the eastern Pacific is resulting in near gale force NW winds across the Gulf of California, as confirmed in a recent scatterometer satellite pass. Seas are estimated to be 10 ft over portions of the central and southern where the fetch is long enough to support developed seas. The upper trough and surface low will lift out to the northeast today ahead of a another trough moving into the western U.S. This will allow winds and seas to diminish across the central and southern Gulf of California through today. Low pressure may deepen over the the northern Gulf of California however, where NW winds to 20 to 25 kt may persist tonight into Fri. Fresh to strong NW winds accompanied by reinforcing NW swell to 13 ft will reach the waters of Baja California Norte through late today. These winds will diminish through tonight, but the NW swell will persist into early next week. Another round of large NW swell will reach Guadalupe Island by Mon night. These successive groups of reinforcing NW swell will maintain combined seas in excess of 8 ft across the open Mexican offshore waters west of 110W through the early part of the week. Farther south, moderate S to SW winds in the Gulf of Tehuantepec may increase slightly by this afternoon as low pressure moves into the western Gulf of Mexico. The next round of gap winds to gale force may start late Sat, as a cold front associated with the low pressure sweeps across the western Gulf of Mexico. These gap wind pulses will gradually diminish through the early part of next week as the high pressure behind the front weakens and shifts east. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Gentle to moderate winds and slight to moderate seas persist across the region. The next round of fresh to fresh gap winds through the Gulf of Papagayo region is possible by late Sat into early Sun. Elsewhere, gentle to moderate winds along with slight to moderate wave heights due to a southwest swell will change little over the Central American and equatorial waters through Mon. REMAINDER OF THE AREA... A 1030 mb high center is analyzed just north of the area at 32N133W, with a ridge stretching southeastward to the Revillagigedo Islands. Recent scatterometer satellite data shows fresh to strong trade wind flow persisting between the ridge and the ITCZ to the south over the deep tropics west of 120W. Concurrent altimeter passes showed wave heights in the range of 8-12 ft north of about 05N and west of 110W likely due to the combination of northeast wind waves with long- period northwest swell. The ridge will weaken through Fri night while it shifts east- southeastward ahead of an approaching cold front, allowing for northeast trades to diminish back to moderate to fresh speeds. Maximum wave heights will be about 10 to 12 ft, and wave heights of 8 ft or greater will remain west of 110W and north of 05N through early next week. The front will stall just to the northwest of the discussion area, but an accompanying set of reinforcing northwest swell with wave heights 12 ft or greater will cover the waters northwest of a line from Baja California Norte to 12N140W Sat night through early next week. $$ Christensen