000 AXPZ20 KNHC 181507 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1507 UTC Thu Aug 18 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. ...SPECIAL FEATURES... A 1006 mb area of low pressure near 17N109.5W is moving to the northwest around 9 kt, with a trough axis extending through the low from 21N109W to 12N109W. This low remains sheared with all of the deep convection located on the southwest side. Scattered moderate and isolated strong convection can be found within 210 nm in the southwest quadrant. Fresh to strong winds and seas of 8 to 9 ft are within 300 nm of the low in the southeast semicircle. In addition, funneling is occurring outside of the circulation along the coast of southwest Mexico with fresh to strong winds found within 60 nm of the coast between 101W and 105W, where seas are also up to 8 ft. The low is forecast to reach to near 20N114.5W by early Saturday morning and currently has a high chance of tropical cyclone development through the next 48 hours. ...TROPICAL WAVES... A tropical wave is analyzed across the isthmus of Tehuantepec southward to 10N moving west at around 10 to 15 kt. Scattered moderate convection can be found within 120 nm either side of the wave axis. A tropical wave is analyzed from 19N134W to 11N134W moving west at around 5 to 10 kt. Weak low pressure that was along the wave axis has dissipated during the past several hours, as has any associated deep convection. Even so, the pressure gradient between this feature and surface ridging to the north is still tight enough to support fresh trades on the northwest side, allowing for an area of combined seas to 8 ft to linger. These seas will subside as the feature reaches 140W by 24 to 48 hours. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 08N77W to 09N90W to 14N103W, then resumes from 14N113W to low pressure near 09N129W to 10N140W. Scattered moderate convection is within 180 nm south of the axis east of 86W, within 90 nm north of the axis between 86W and 91W, from 14N to 16N between 99W and 102W, and also within 75 nm either side of the axis between 114N and 119W. Additional scattered moderate convection can be found offshore of central Mexico from 20N to 24N east of 108W. This activity developed along the coast during the overnight hours before propagating offshore early this morning. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface ridge extends across the area north of 20N between 110W and 120W. The latest observations indicate gentle to moderate northerly flow around this ridge north of 20N, with combined seas of 4 to 7 ft. Meanwhile light to moderate southerly flow prevails in the Gulf of California with a north to south trough located along the eastern shore of the Baja California peninsula. Little change in these conditions is anticipated through the next several days, except winds may pulse to moderate to fresh just offshore of the western coast of the Baja California peninsula late this weekend into early next week as the pressure gradient tightens slightly. To the south of 20N, the main influence is the 1006 mb surface low currently analyzed near 17N109.5W. Please refer to the special features section above for details on the potential impacts of this low. Otherwise, fresh to strong offshore winds in the Gulf of Tehuantepec will diminish in the next few hours, with moderate to fresh offshore flow anticipated during the overnight hours through early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to locally fresh northeast to east offshore winds are expected across, and just downstream of the Gulf of Papagayo through mid morning today, and then expected to develop again tonight. Otherwise, light to moderate winds will prevail on either side of the monsoon trough through early next week with combined seas of 4 to 7 ft. REMAINDER OF THE AREA... A surface ridge extends into the area from 32N136W to 25N116W. Moderate to locally fresh trades and combined seas of 4 to 7 ft dominate the remainder of the basin. The ridging is forecast to break down as a decaying cold front or remnant trough drop into the northern portion this weekend, stalling and lingering over the northwest portion through early next week. This will allow for trades to diminish to mainly light to moderate as the pressure gradient weakens. $$ LEWITSKY