000 AXPZ20 KNHC 121515 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sat Sep 12 2020 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 1006 mb low pressure is centered along the monsoon trough near 15.5N110W, and anchors the eastern end of an elongated cyclonic, low-level circulation that extends W-NW to a 1007 mb low near 17N119.5W. Numerous moderate scattered strong convection is noted from 10N to 17N between 107W and 115W. Seas are likely 7-9 ft south of the low, within the fresh to strong monsoonal flow associated with the broad circulation. Environmental conditions appear conducive for development, and a tropical depression is likely to form over the weekend or early next week while the system moves west-northwestward away from the coast of Mexico. This system has a high chance of tropical cyclone formation within the next 48 hours. For more information, see the latest eastern North Pacific Tropical Weather Outlook at https://hurricanes.gov. ...TROPICAL WAVES... A tropical wave axis is along 117W south of 18N, moving westward at 10 kt. Scattered moderate convection is noted from 08N to 16N within 60 nm of the wave axis. A tropical wave extends along 90W across Guatemala and into the eastern Pacific, moving westward at 10-15 kt. Scattered moderate isolated strong convection is occurring from 08N to 14N between 90W and 96W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N76W to 08N81W to 11N88W to 10N97W to 1006 mb low pressure near 15.5N110W to 1007 mb low pressure near 17N119.5W to 11N140W. Scattered strong convection is noted N of 04N E of 80W. Scattered moderate isolated strong convection is occurring within 120 nm N of the monsoon trough between 85W and 88W, and within 180 nm NW quadrant of low pressure near 17N119.5W. Scattered moderate convection is noted within 120 nm S of the monsoon trough between 125W and 130W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for more details on the potential for tropical cyclone development associated with low pressure near 15.5N110W. The low is expected to gradually become better organized and will increase winds and seas across the outer waters offshore of Manzanillo and Cabo Corrientes, shifting west-northwest to near Clarion Island through the weekend. Elsewhere, generally tranquil marine conditions prevail across the waters near the Baja California peninsula, and along the coast of southern Mexico. GOES-16 satellite imagery and lightning data show a mesoscale convective system moving off the coast of Sinaloa and over the entrance to the Gulf of California. Note that gusty winds and locally higher seas are possible in and near strong thunderstorms. Fresh northerly gap winds across the Gulf of Tehuantepec are expected to diminish this afternoon. Modest pulses of moderate to fresh northerly gap winds can be expected each of the next few nights across the Tehuantepec region. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Tranquil marine conditions should prevail for the next several days, with light to gentle winds north of the monsoon trough along about 10N, and gentle to moderate southerly flow south of the monsoon trough. Background S to SW swell will continue impacting the waters for the next several days, although no significant long-period swell events are expected at this time. REMAINDER OF THE AREA... Please see the Special Features section above for more details on the potential for tropical cyclone development associated with low pressure near 15.5N110W. Elsewhere, 1007 mb low pressure centered near 17N119.5W is producing scattered moderate isolated strong convection within 180 nm NW quadrant. This system has a low chance of tropical cyclone formation during the next 48 hours. Some slight development of this system is possible during the next day or two before it interacts with, and is possibly absorbed by, the low pressure system highlighted in the Special Features section. Elsewhere, 1019 mb high pressure centered near 32N131W extends across the waters N of 20N and W of 130W. Gentle to moderate NE trades continue south of this high and north of the monsoon trough axis, with 5-7 ft seas. Generally moderate S to SW flow prevails south of the monsoon trough across the eastern Pacific, with 5-7 ft seas. Fresh to strong winds and 7-9 ft seas are found between 108W and 117W, south of the low pressure system being monitored for potential tropical development. Long-period S to SW swell is present east of 120W, contributing to combined seas of 7-8 ft near the equator. Seas will gradually subside through Sun night. However, a new set of southerly swell may move through the far southern waters during the early to middle parts of next week. $$ B Reinhart