000 AXPZ20 KNHC 120241 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Sep 12 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 0000 UTC surface analysis and satellite imagery through 0200 UTC. ...SPECIAL FEATURES... An area of low pressure is centered along the monsoon trough near 14.5N109W. Convection surrounding this feature has increased in coverage this afternoon and evening, with bands of showers and thunderstorms starting to develop across the western semicircle. An early afternoon ASCAT pass showed 20 to near 25 kt winds occurring from 90 to 210 nm across the northern semicircle. Conditions are forecast to be conducive for further development of this disturbance, and a tropical depression is likely to form within the next couple days, while the system moves WNW at near 10 kt. This system has a high chance of tropical cyclone formation during the next 48 hours, and also a high probability for development within the next 5 days. Also, most global models suggest gale force winds will develop across the north half of this low within 48 hours, and a gale warning has been issued for 0000 UTC Sat to reflect the imminent development of these winds. Please refer to the latest eastern North Pacific Tropical Weather Outlook for more information. ...TROPICAL WAVES... The axis of a tropical wave is along 85W/86W, moving W around 10 kt. Scattered moderate isolated strong convection is noted over waters N of 06.5N to the east of 87W. The axis of a tropical wave is along 100W/101W, moving W around 10 kt. Scattered moderate to strong convection is noted from 10N TO 16N between 95W and 102W. The axis of a tropical wave is along 109W/110W with an associated 1008 mb low pres near 14.5N109W, moving W 10-15 kt. Scattered moderate to strong convection is noted within 270 nm of center except 240 nm across the SE quadrant. This disturbance is being monitored for the potential of tropical cyclogenesis. Please see special features section above for more information. The axis of a tropical wave is along 128W, moving W near 10 to 15 kt. Scattered moderate to strong convection is noted from 09N TO 14.5N between 121W and 133W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08.5N74.5W TO 09N94W TO low pressure near 14.5N109W TO 10N140W. Other than the convective areas described above in the tropical wave section, no significant convection is noted elsewhere. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge over the offshore forecast waters W of Baja California peninsula will slowly weaken through Thu night, then strengthen slightly Fri through Sat. A surface trough will meander between Baja California and the Gulf of California. This pattern will generally produce gentle to moderate northerly winds across the offshore waters for the next several days, then become fresh Fri and Sat. Mainly gentle NW winds are expected across all but the far north portions of the Gulf of California. Fresh to strong E to SE winds were noted in an afternoon scatterometer pass off the coasts of Michoacan to Jalisco, beyond 120 nm of the coast, in an area of strong convection occurring on the NE edge of the developing low pressure discussed above. Seas are assumed to remain at 7-9 ft in this area of strong winds. This area of wind and weather will shift westward of 110W and out of the offshore waters tonight. Farther south, strong to near gale force northerly gap winds are expected to pulse at night across the Tehuantepec region tonight through Sat night as low pressure forms over the southwest Gulf of Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh NE to E winds will generally prevail over the Gulf of Papagayo region through the forecast period. Elsewhere, mainly light to gentle winds will persist north of the monsoon trough, with gentle to moderate S to SW winds south of the monsoon trough for the next several days. Very active convection associated with a tropical wave across Central America will shift westward of Costa Rica and the Papagayo region tonight through Thu. REMAINDER OF THE AREA... A broad area of low pressure is centered several hundred miles southwest of Acapulco, Mexico near 14.5N109W. This disturbance has the potential to develop into a tropical cyclone. Regardless of tropical development, models suggest that gale force winds will develop across the northern half of the low by Fri evening as the low continues to move WNW. Seas at that time are expected to build to 10-11 ft within the gale force winds. Please see the special features section above for more information. High pressure centered N of the area will maintain moderate NE winds N of the monsoon trough and W of 125W through Sat. Seas across this tradewind belt will run 6-9 ft in mixed southerly swell. Cross equatorial swell is propagating across the tropical Pacific waters. Seas of 8 ft or higher cover the area generally south of 12N between 105W and 130W. Wave heights will slowly start subsiding on Thu, except in the vicinity of the developing low pressure as it tracks to the WNW passing to the southwest of the Revillagigedo Islands through Fri. $$ Stripling