000 AXPZ20 KNHC 302349 AAA TWDEP Tropical Weather Discussion...Updated NWS National Hurricane Center Miami FL 2349 UTC Wed Dec 30 2020 Updated Offshore Waters Within 250 nm of Mexico section 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N79W to 09N86W to 06N93W to 05N100W and to 06N108W, where latest scatterometer data indicates that it transitions to the ITCZ and continues to 07N120W to 06N130W and to beyond the area at 06N140W. Scattered moderate to isolated strong convection is 180 nm north of the ITCZ between 125W-130W and within 120 NM north of the ITCZ between 130W-133W. Scattered moderate convection is within 180 nm south of the trough between 78W-80W, also within 120 nm south of the trough between 78W-80W, within 60 nm south of the ITCZ between 126W-130W and between 133W-136W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO...Updated The gradient associated with high pressure ridging over this part of the area is allowing for fresh to strong northwest winds to exist over these waters. Fresh to strong northwest winds are across the Gulf of California. Wave heights are in the range of 9-11 ft over the offshore waters and less than 8 ft in the Gulf of California. The 9-11 ft wave heights are embedded within a large set of northwest swell that has its leading edge of wave heights to 8 ft reaching as far south as the Revillagigedo Islands. A very pronounced mid to upper-level trough is swinging southeastward along a position, as interpreted from water vapor imagery, from northeastern Arizona, southwestward to over northwestern Mexico and to offshore Baja California Sur near 20N113W. This feature will move eastward through this morning, supporting lower pressure over the southern Plains and north central Mexico. Ridging will build behind this trough over the Great Basin and eastern Pacific, tightening the pressure gradient and allowing for the present northwest winds over the Gulf of California to increase to near gale force over the central and southern Gulf of California during this afternoon and tonight along with wave heights building to or near 9 ft. Northwest winds will increase to fresh to strong speeds off Baja California Sur by late Wed. The aforementioned northwest swell will continue to propagate southward, with resultant wave heights to 8 ft reaching as far south as Cabo Corrientes by Thu night. The fresh to strong northwest winds will diminish Thu as the high pressure north of the area shifts east. But another, weaker deep-layer trough moving through the region will support strong NW winds in the northern Gulf of California Thu night, and off Baja California Norte with a reinforcing set of northwest swell raising wave heights to 12 ft. Winds and seas diminish Fri into Sat. Wave heights exceeding 8 ft will continue off Baja California due to a northwest swell. Looking ahead, another set of northwest swell is forecast to propagate into the area, with wave heights building significantly to the range of 12-14 ft in the waters north of Cabo San Lazaro late Sat through Sun night. Farther south, scatterometer data from this morning over the Gulf of Tehuantepec region suggested that winds there have diminished to gentle to moderate speeds over that region. Residual swell from the earlier gap winds is subsiding, and wave heights are likely in the range of 5-7 ft primarily due to long- period southwest swell. Looking ahead, the next gale force gap wind event in the Gulf of Tehuantepec is expected by late Sat through Sun night as a cold front moves through the Gulf of Mexico and high pressure in its wake ridges southward across eastern Mexico and toward the Gulf of Tehuantepec region. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Fresh to locally strong northeast gap winds across the Gulf of Papagayo region have diminished to mainly fresh speeds this afternoon. Wave heights have subsided to a maximum of 5 ft there, with little change through the rest of the week. The next round of fresh to fresh gap winds 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 Sun night. REMAINDER OF THE AREA... A 1034 mb high center is analyzed just north of the area at 32N134W, with a ridge stretching southeastward to the Revillagigedo Islands. Afternoon ASCAT data passes indicate that the pressure gradient resulting from the interaction between the ridge and the ITCZ to the south is producing fresh northeast to east trades over the deep tropics west of about 127W, with a pocket of fresh to strong trades present from 18N to 24N west of 130W. The trades will expand eastward to near 120W tonight as the ridge strengthens. A recent altimeter pass showed wave heights in the range of 8-11 ft north of about 07N and west of 110W likely due to the combination of northeast wind waves with long-period northwest swell propagating through this part of the discussion area. The ridge will weaken Thu 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 or 11 ft, and wave heights of 8 ft or greater will remain west of 110W and north of 04N through Fri. The cold front is forecast to become stationary near 30N140W by late Fri, but a reinforcing set of northwest will accompany the front with wave heights 12 ft or greater covering the waters northwest of a line from Baja California Norte to 12N140W by Sat night through Sun. $$ Aguirre