000 AXPZ20 KNHC 091523 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Sep 9 2024 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 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. ...TROPICAL WAVES... A tropical wave is along 98W from 07N to inland over southern Mexico, moving west at 5 to 10 kt. Associated convection is described below in the ITCZ/Monsoon trough section. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 13N87W to 16N110W to a 1011 mb low pressure near 13N128W to beyond 13N140W. Scattered moderate to isolated strong convection can be found from 08N to 11N between 85W and 87W. Scattered moderate convection is noted from 10N to 15N between 95W and 105W, and from 11N to 13N between 115W and 119W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A recent scatterometer satellite pass indicated moderate to locally fresh E to SE winds off the coasts of the states of Guerrero and Michoacan, likely associated with a decaying area of showers and thunderstorms, and ahead of an active tropical wave moving across southern Mexico. A concurrent altimeter satellite pass showed 4 to 6 ft seas in this area as well. Pressure is lowering across this area along the monsoon trough, but currently the pressure gradient is fairly weak, only supporting light to gentle breezes across the remaining open offshore waters of Mexico, with 3 to 5 ft seas. Calm to light breezes and slight seas are noted over the Gulf of California. For the forecast, pressure will probably continue to lower over the region between Cabo Corrientes and the Revillagigedo Islands through mid week as the tropical wave continues westward. This pattern will support fresh SW winds and building seas off Jalisco and Colima into Wed. Looking ahead, environmental conditions are forecast to be conducive for some gradual development of the lower pressure, and a tropical depression could form during the middle to latter part of this week while it moves generally north-northwestward, near the coast of southwestern Mexico. Currently, this system has a low chance of tropical cyclone formation in the next 48 hours and a medium chance in the next 7 days. Please refer to the latest NHC Tropical Weather Outlook at www.hurricanes.gov for more information about this system. Farther north, a tightening surface pressure gradient between high pressure in the Pacific and falling pressure in northern Mexico will support moderate to fresh NW winds and moderate to rough seas in NW swell N of Punta Eugenia Tue through Thu night. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Earlier scatterometer data showed gentle to moderate winds on either side of the monsoon trough that is crossing along 12N-13N. Seas are generally 4 to 7 ft. For the forecast, gentle to moderate S to SW winds will continue through much of the week south of the monsoon trough, with locally fresh winds possible Wed into Thu. North of the trough, light to gentle winds will prevail. Moderate seas in primarily SW swell will continue through this week, with the highest seas in the 6 to 7 ft range offshore of Guatemala and El Salvador through Tue night, and between Ecuador and the Galapagos Islands through Wed. ...REMAINDER OF THE AREA... A recent pair of altimeter satellite passes indicate 6 to 8 ft combined seas roughly from 05N to 10N between 100W and 110W. This is an indication of SW swell, but also likely increasing SW winds this area, flowing into the lowering pressure area to the north. Convergence of these SW winds are supporting clusters of showers and thunderstorms along the monsoon trough as well. Gentle to moderate winds and 4 to 6 ft are noted elsewhere east of 110W. Farther north, moderate to fresh N to NE winds and 4 to 6 ft are noted north of 20N between 120W and 130W, between high pressure west of this area and a trough over Baja California. Gentle to moderate winds and moderate seas in mixed swell are noted elsewhere. For the forecast, SW winds will increase through mid week with building seas north of 10N between 105W and 120W related to the lowering pressure off southwest Mexico. Meanwhile surface ridging will build north of 20N and west of 120W, promoting moderate to fresh NE winds and seas of 4 to 6 ft trough through much of this week. $$ Christensen