000 AXPZ20 KNHC 211359 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1249 UTC Wed Jun 21 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends along the Central American coast or just inland from Panama to the Gulf of Tehuantepec in southern Mexico. The monsoon trough emerges off the coast near 16N95W to 09N130W. The intertropical convergence zone continues form 09N130W to beyond 08N140W. Scattered moderate convection is noted within 120 nm south of the monsoon trough axis between 105W and 125W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Moderate to fresh northerly flow is noted off Baja California Norte between troughing over the the peninsula and ridging well to the northwest. This is supporting moderate to fresh southerly winds over the Gulf of California as well. Northerly swell of 8 to 9 ft is propagating into the waters off Baja California Norte beyond 90 nm, expected to decay below 8 ft into Fri. Elsewhere, the weak troughing across the Gulf of California and into the adjacent Pacific waters off Baja California are maintaining generally light to gentle breezes across the region. The troughing over the Baja California will move west through Thu, enhancing southerly flow near Los Cabos and across much of the Gulf of California into Sat when the gradient relaxes. Upper divergence may support a few showers and thunderstorms over the east coast of the Gulf of California tonight emerging off higher terrain to the east. Farther south, a weak low level circulation may be emerging off the coast of northern Central America heading westward into the Gulf of Tehuantepec. This is related to a broad mid level feature over northern Central America. This will support moderate to fresh east to southeast winds off the coasts of Chiapas and Oaxaca Fri and Sat as the broad weak low shifts west. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate southwest to west winds are expected across the entire forecast area today, then the pressure gradient will gradually relax with a gentle southwest breeze continuing through Sunday night, except will increase to moderate south winds of 06N Sat night into early next week. Long period SW swell of 5 to 7 ft will gradually decay this weekend. REMAINDER OF THE AREA... A ridge dominates most of the waters north of the convergence zone. Scatterometer and altimeter passes continue to indicate an area of moderate to fresh winds and seas of 8 to 10 ft roughly north of 20N and west of 120W. The ridge will continue to dominate the waters north of the convergence zone today, shifting west as troughing developing near the Baja California peninsula also drifts west. A broad and weak low pressure is forecast to develop along the trough axis near 18N120W by tonight. Northerly swell will continue to propagate across the waters north of 20N, building to 10 to 12 ft north of 27N Thu through Fri as fresh swell moves in around a low pressure system north of the area. Seas will decay through the upcoming weekend as the low moves northwest while weakening. $$ Christensen