000 AXPZ20 KNHC 211604 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Sep 20 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... A broad area of low pressure along the southwest coast of Mexico has a pair of low pressure centers analyzed near 15N97W 1010 mb and 17N103W 1008 mb. The area of low pressure is enhancing SW monsoon flow between 100W and 115W, producing active convection along the Mexico coast north of 16N between 102W and 106W. Model guidance indicates this area of low pressure will consolidate over the next 24-48 hours, with a tropical depression likely to form in about 2-3 days. Environmental conditions are favorable for development into a tropical cyclone as the broad low moves slowly west-northwest. Extensive heavy rain is expected in parts of southern Mexico during the next several days. ...TROPICAL WAVES... A tropical wave along 90W north of 07N is moving west at 10 kt. Scattered moderate convection is from 08N to 11N within 150 nm east of the wave. The wave is expected to eventually become absorbed into the larger monsoon circulation described above. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough stretches across the entire basin from Panama near 08N78W to low pres near 17N103W 1008 mb to 14N107W to 11N127W to 12N140W. Scattered moderate to strong convection is from 13N to 19N between 101W and 107W. Scattered moderate isolated strong convection is from 10N to 12N between 93W and 96W. Scattered moderate convection is within 120 nm south of the trough axis west of 112W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weak surface ridge reaches the central part of Baja California near 27N. An approaching cold front moving south across the waters west of California is producing fresh to strong SW winds in the northern part of the Gulf of California, expected to persist through early Fri morning, with seas building to 5-6 ft north of 30N. The local effects will be less evident west of Baja California and south of 29N in the Gulf of California. Elsewhere, the possible development of low pressure along the southern coast of Mexico will increase winds and seas between 100W and 107W the next few days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... An active monsoon trough along the coast of Central America from Guatemala to Panama will help maintain active convection across coastal waters the next few days. Expect SW winds south of the trough to strengthen gradually to 20-25 knots through Saturday. Further south, gentle to moderate southerly winds are expected to persist south of 05N through the weekend. REMAINDER OF THE AREA... The post-tropical remnant low of Norma is near 23N117W as a swirl of low and mid level clouds and stratiform precipitation. Winds are estimated to be 20 kt near the center and seas to 7-8 ft. The low will move slowly and steadily weaken through Friday. The post-tropical remnant low of Otis is near 16N133W as a swirl of low level clouds and limited stratiform precipitation. Fresh to strong N-NE winds and 8 ft seas are within 150 nm NW of the low center. The low is expected to move SW and weaken into a trough through Friday, with seas gradually diminishing to 6-7 ft. NW swell associated with strong N-NW winds north of the area is producing combined seas of 8-10 ft north of 25N between 118W and 127W, and is expected to contract and shift eastward through Friday. Another weaker round of NW swell associated with a cold front west of California is expected to arrive Fri night. High pressure centered well N of the area and lower pressure associated with the convergence zone will maintain moderate trade winds west of 120W through the weekend. $$ Mundell