000 AXPZ20 KNHC 161523 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1521 UTC Tue Aug 16 2016 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 is along 98W north of 10N, moving slowly westward near 10 kt. Very active convection continues near the axis as is described in the section below. This active weather will shift westward today from the Tehuantepec region. A tropical wave is along 106W-107W from 08N to 18N, also moving slowly westward near 10 kt. Scattered moderate convection associated with this wave was noted mainly near the monsoon trough as is described in the section below. Global model guidance continues to suggest that a broad low pressure area will gradually develop from this wave during the next few days as it shifts to the west-northwest. A tropical wave is near 127W from 12N to 20N, with an associated 1008 mb surface low center near 17N127W. Convection has diminished overnight associated with this low center, and overnight scatterometer data indicated winds of 20 kt or less, with associated seas less than 8 ft. The wave and low are expected to continue to shift westward near 10 to 15 kt and gradually weaken as environmental conditions become less conducive for further development of this system. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis is from 08N78W to 13N103W to 10N115W to low pressure near 16N127W to 13N140W. Scattered moderate convection is within 120 nm south of the axis east of 86W, within 180 nm either side of the axis between 89W and 102W, within 90 nm either side of the axis between 104W and 112W, and also within 90 nm either side of axis west of 134W. ...DISCUSSION... N of 15N E of 120W: The NE Pacific ridge extends southeastward into the area to near the Revillagigedo Islands. The pressure gradient between the ridge and a surface trough over Baja California is supporting mainly moderate northwesterly winds over the coastal waters of Baja California Norte, while light to gentle northwest to west winds generally extends from Punta Eugenia to offshore of Cabo Corrientes. Seas continue in the 4 to 6 ft range across this area in mixed NW and SW swell. Light and variable winds prevail inside the Gulf of California. Little change in these overall marine conditions are expected during the next few days, with winds increasing modestly each late afternoon and evening along the Baja peninsula due to day time heating. S of 15N E of 120W: Gentle to moderate east to southeast winds generally prevail north of the monsoon trough from the Papagayo area to the Gulf of Tehuantepec area, then are gentle south to southeast from Tehuantepec to Cabo Corrientes as indicated by overnight scatterometer data. Gentle to moderate south to southwest winds prevail south of the monsoon trough. Seas are running in the 4 to 6 ft range in southwest swell across much of this area, but an area of combined seas of 6 to 8 ft south of the monsoon trough between 104W and 107W, where southwesterly winds are around 15 to 20 kt. The monsoon trough has begun to lift northward to along 14N west of Tehuantepec in response to the tropical wave along 106W-107W, and will lift slightly further to 15N along 110W by late tonight. The coverage in 15 to 20 kt winds will expand during the next 24 to 48 hours allowing for combined seas to the south of the monsoon trough to build to 8 to 9 ft seas between 107W and 112W by 48 hours. Otherwise, light to moderate offshore winds will generally prevail across the Papagayo region through the week, except pulsing to 20 kt during the late night and early morning hours with nocturnal drainage flow. Mainly light and variable winds will prevail in the Tehuantepec region through the week, except increasing to fresh during the late night and early morning hours. Southwest cross equatorial swell will move into the area waters later this morning and build seas south of 03N to 6 to 8 ft through mid-week before decaying. W of 120W: High pressure of 1029 mb centered near 39N140W extends a ridge southeast to near 25N120W. The pressure gradient between this area of high pressure and low pressure within the monsoon trough is producing moderate to fresh trades to the north of the monsoon trough where seas are in the 5 to 8 ft range. Gale force winds off the west coast of the United States will generate a northerly swell that will propagate into the north waters by Wednesday evening, decaying to less than 8 ft by Friday. $$ LEWITSKY