000 AXPZ20 KNHC 212212 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 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 1800 UTC surface analysis and satellite imagery through 2115 UTC. ...SPECIAL FEATURES... A broad area of low pressure across the southwest coast and coastal waters of Mexico persists this afternoon, where a weak surface low pressure center is analyzed near 17N103.5W at 1008 mb. Just to the south of this, a broad area of fresh to strong SW monsoonal winds prevail between 97W and 112W, producing active convection across this area and creating a very unstable atmosphere. Computer model guidance indicates that low pressure center in this general area will shift slowly WNW and become better organized over the next 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 across parts of southern Mexico and Central America during the next several days. ...TROPICAL WAVES... A tropical wave along about 90W north of 07N is moving slowly west and beginning to lose identity. Scattered moderate to strong convection is from 07.5N to 15N between 86w and 95w associated with the wave. The wave is expected to eventually become absorbed into the larger monsoonal circulation described above. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough stretches across the entire basin from Panama near 09.5N74.5W TO 08N80W TO low pres near 17N103.5W 1008 MB TO low pres near 10N136.5W 1012 MB TO beyond 12N140W. Scattered moderate to strong convection is within 60 nm N and 240 nm S of the trough between 85W and 108W and between 112W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weak surface ridge extends ESE across the northern portions of the discussion area to the central part of Baja California near 26N. An approaching cold front moving south across the waters west of California is aiding in 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 5-7 ft north of 29N. 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 23N117.5W 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 7-9 ft. The low will move slowly and steadily weaken through Friday. The post-tropical remnant low of Otis is near 15N133.5W as a swirl of low level clouds and limited stratiform precipitation. Fresh 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 21N between 117W and 140W, 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. $$ Stripling