000 AXPZ20 KNHC 271018 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Fri Sep 27 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... An elongated trough of low pressure meanders form NW Colombia northwestward across Central America to southern Mexico near 18.5N012W, across the state of Michoacan, then west to a weakening low pressure center near 17N110W. Strong W to SW surface to low level winds have developed south of this trough, roughly from 08.5N to 14N between 90W and 106W. This strong monsoonal wind flow is transporting abundant tropical moisture into the near and offshore waters of southern and southwestern Mexico, and is fueling clusters of strong thunderstorms form 10N to the Mexican coast from just east of Acapulco to the Mexico Guatemala border. Strong thunderstorms producing very heavy rainfall will continue across this area during the next 24 hours and affect the coastal zones and western slopes of the Sierra Madre occidentales. Heavy rainfall amounts could produce areas of flash flooding and landslides from Oaxaca to Michoacan through the weekend. Please refer to local weather information issued by the Mexican Meteorological Service. In addition, a low pressure center is expected to form along this trough during the next couple of days, and it is likely to become a tropical depression or storm over the weekend or early next week while it moves WNW to NW at 10 to 15 mph near or along the southern and southwestern coasts of Mexico. Regardless of development, heavy rainfall, with the possibility of flash flooding and mudslides, is likely along the Pacific coasts of Central America and southern and SW Mexico during the next several days. This developing low pressure system has a medium chance of becoming a tropical cyclone during the next 48 hours and a high chance of becoming a tropical cyclone during the next 5 days. ...TROPICAL WAVES... None. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N75W TO 18.5N103W TO LOW PRES NEAR 17N110W TO 10.5N133W TO BEYOND 12N140W. Scattered to numerous moderate to strong convection is seen from 10N TO 17N BETWEEN 90W AND 104W. Scattered moderate isolated strong convection is elsewhere from 08N TO 18N BETWEEN 84W AND 108W. Widely scattered moderate isolated strong convection is within 75 nm N and 120 nm S of the trough between 123W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Overnight scatterometer data revealed light to gentle winds across the Baja California Norte offshore waters, while fresh northwest winds were observed south of Punta Eugenia to Cabo San Lucas. Seas were generally 4-7 ft in NW swell across these waters. Farther south and southeast, moderate to fresh NW winds prevailed from the entrance to the Gulf of California to Acapulco then became moderate westerly winds to the Gulf of Tehuantepec. Scatterometer winds also captured a low pressure center near 17N110W, where 20-25 kt were seen within 75 nm across the western semicircle. This low was moving quickly ESE and it is embedded in the mean westerly low level wind flow across the region. High pressure behind a weakening cold front will build weakly across the Baja waters over the weekend to freshen the NW wind flow across the Baja California Norte waters, and bring increased NW swell. Little change in the pattern is expected elsewhere to the north of Cabo Corrientes over the weekend. Winds and seas occurring south of the monsoon trough will lift northward with the developing low pressure system described above, and will also be accompanied by increasing strong thunderstorm activity. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh SW to W monsoon flow will support showers and thunderstorms off the coasts of Guatemala and El Salvador today through Sat, as an area of low pressure is expected to develop off the southern coast of Mexico, between Tehuantepec and Guatemala. Offshore wave heights will build to 7-9 ft today, with seas to 8 ft spreading eastward towards the coastal waters of Nicaragua and northern Costa Rica tonight through the weekend. REMAINDER OF THE AREA... Light to moderate NE trade winds will persist north of 17N and west of 130W for the next couple days. Elsewhere, long period N swell is producing 7 to 9 ft seas roughly north of 27N and west of 125W, based on recent altimeter data. Wave heights will peak around 10 ft today. A cold front will drop southward into the northern waters and weaken this weekend. Expect moderate to fresh NE winds to develop north of 26N and west of 125W on Sun following frontal passage. $$ Stripling