000 AXPZ20 KNHC 302102 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2102 UTC Fri Jun 30 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. ...TROPICAL WAVES... A tropical wave analyzed along roughly 100W from 06N to 13N, moving west at 10 to 15 kt. Scattered moderate convection associated with the wave is observed from 07N to 11N between 99W and 103W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from Costa Rica to 10N95W to 11N115W. Recent scatterometer data indicates an elongated area of low pressure may be forming along the monsoon trough near 10N90W. Scattered moderate convection is wrapping into this area, from 06N to 09N between 85W and 92W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Weak 1012 mb low pressure, the remnant of Dora, centered near 21N117W is breaking up the subtropical ridge positioned farther to the northwest. Scatterometer and ship data show this is maintaining gentle to moderate breezes across the region, except for pulses of 15 to 20 kt winds off Los Cabos. The low will fill through tonight allowing the ridge to build east. This in turn will allow winds to increase across the waters off Baja California north Cabo San Lazaro. Northerly swell to 7 ft will reach Guadalupe Island off Baja California Norte by early Sat, following a trough moving into Southern California and northern Baja California Norte. Elsewhere seas will be 4 to 6 ft off Baja California. Similarly, southerly flow will increase across the Gulf of California late Sat into Sun ahead of the trough, possibly reaching 20 to 25 kt over the far northern Gulf by early Sun. Given limited duration of the winds, seas will not build substantially, remaining 2 to 4 ft overall. Farther south, pulses of fresh to strong gap winds will set up through the Gulf of Tehuantepec each evening, due in part to tighter pressure gradient related to broad low pressure developing along the monsoon trough farther south. The gap winds are enhanced by overnight drainage flow, and diminish later in the morning. Seas may briefly reach 8 ft by late morning, aided in part by a component of long period southerly swell. Seas of 5 to 7 ft primarily in southerly swell will reach as far as 20N through early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Strong trade winds over the southwest Caribbean are reaching across southern Central America into the Gulf of Papagayo. This is depicted well by a 16 UTC scatterometer pass. This is enhancing convection and broad rotation centered along the monsoon trough. Global models show this may remain pretty disorganized, with a more organized low pressure area forming along the monsoon trough and tropical wave by late Sat or early Sun near 10N100W. The Papagayo gap winds weaken through Sat, but southerly swell will continue to propagate through the region with 6 to 8 ft seas into Sun, the decaying to 4 to 6 ft seas early next week. REMAINDER OF THE AREA... A weak trough near 11N115W will continue to move west through Sun, accompanied by scattered showers and thunderstorms. Farther west, earlier showers and thunderstorms, related to an upper trough west of the region were active near 1013 mb low pres centered at 12N132W. The low will weaken through tonight into a trough, but remain in place through early next week. Ridging will gradually build north of the region, with gentle to moderate northeast breezes increasing to moderate to fresh with 5 to 7 ft seas. Southerly swell with combined seas of 6 to 8 ft encompasses the region reaching as far north as 10N east of 120W. This southerly swell will decay below 8 ft by late Sun. $$ Christensen