570 AXPZ20 KNHC 041621 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Oct 4 2018 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 1500 UTC. ...SPECIAL FEATURES... Major Hurricane Sergio is centered near 15.0N 119.3W 943 MB AT 1500 UTC, or about 775 nm SW of the southern tip Baja California, moving NW at 8 kt. Maximum sustained winds remain 120 kt with gusts to 145 kt. Little change in intensity is expected during the next 12 hours as Sergio continues to move NW. Sergio is then expected to move WNW tonight and then veer more westward on Fri, and will likely diminish slightly in intensity as it begins to gradually move over slightly cooler waters. Numerous strong convection is seen on satellite imagery this morning within 45 nm N and 90 nm S semicircles, while additional bands of scattered moderate to strong convection are occurring elsewhere within 120 nm NW and 210 nm SE semicircles. Large swell generated from Sergio will impact the Pacific coasts of Mexico and southern California during the remainder of this week. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from low pressure across the SW Caribbean near 15.5N81.5W to 11.5N95W to 14N109W, then resumes SW of Sergio from 12N124W to 11.5N135W to beyond 10N140W. Scattered moderate to strong convection is from 06.5N to 13.5N between 83W and 97W, and within 120 nm of trough between 124W and 132W. Scattered strong convection is from 06.5N to 12.5N between 135W and 142W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features above for information on the impacts of Hurricane Sergio. A weakening frontal trough extends from low pressure offshore of central California through 30N123W to 22.5N135W. The trough will continue to move eastward and become diffuse by the time it reaches the Baja Peninsula on Fri. High pressure building SE behind the boundary will freshen NW winds across the offshore waters of Baja California late today, with building seas in NW swell. A strong surge of southerly swell from Sergio is moving into the area waters this morning, and was depicted by an early morning altimeter pass with 6-11 ft seas across the waters from Manzanillo to Cabo San Lazaro along Baja California Sur. Expected building seas across the entire area today, peaking at 8-12 ft, and impacting the entrance of the Gulf of California. Large and dangerous surf will dominate the coastal zones into the weekend, including the southern the Gulf of California. Gentle NW to W winds will prevail across most of the Gulf of California today. As high pressure builds across the area tonight and Fri, NW winds will freshen across the Gulf. Moderate NW winds will generally prevail across the waters between Cabo San Lucas and the Gulf of Tehuantepec for the next few days, while large SE swell from Sergio dominates area seas. In the Gulf of Tehuantepec, offshore northerly gap winds of 20 to 25 kt are expected to pulse to near 30 kt during overnight hours through Fri. Seas will reach 9-10 ft during the period of strongest winds. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough will meander between 09N and 12N, with fresh to strong southwesterly flow and building seas to 9 ft expected S of the monsoon trough E of 100W through Sat, as a broad low pressure area develops across the western Caribbean and Central America. This broad area of low pressure and the fetch of SW winds across the tropical Pacific will transport abundant moisture into portions of Costa Rica, Nicaragua, and western Panama, and will produce significant rainfall through early next week. Isolated areas could see 20 inch rainfall accumulations by Mon. Refer to your local meteorological service for specific information on this potentially dangerous pattern. REMAINDER OF THE AREA... See Special Features above for information on Hurricane Sergio. As mentioned above, a frontal trough across the northern waters will gradually become diffuse during the next 24 hours, as it sweeps eastward across Baja California Norte early Fri. NW swell behind the trough will combine with fresh NE winds to build seas to 9-10 ft later today, then merge with the large and growing area of mixed swell associated with Hurricane Sergio on Fri. $$ Stripling