000 AXPZ20 KNHC 131520 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Fri Oct 13 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 extends from northern Colombia near 09N76W across the Pacific to 08N94W to 12N107W to 1008 mb low pressure near 12N111W to 11N127W to 10N140W. Convection associated with a tropical wave near Panama is discussed below. Scattered moderate convection is noted from 08N to 14N between 104W and 117W, and within 45 nm south of the trough axis between 120W and 136W. ...TROPICAL WAVES... A tropical wave across Panama along 80W/81W from 05N-13N is moving west into the Pacific at 10 kt. The wave is in a low shear environment and TPW imagery shows abundant moisture. Scattered moderate isolated strong convection is from 03N-09N east of 81W, where the wave interacts with the monsoon trough. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface ridge extends across the waters off Baja California. The pressure gradient between the ridge and a trough over the Gulf of California is supporting gentle to moderate NW winds in the offshore waters of Baja California. Seas of 7 to 9 ft in northerly swell are spreading across forecast zone PMZ011, with seas 6-7 ft in the Sebastian Vizcaino Bay. Seas of 4 to 6 ft are noted elsewhere. The ridge will remain in place through Saturday will little change in winds. By Saturday evening, expect seas of 5-7 ft across most of the offshore waters W of 110W. On Sunday, marine guidance suggests increasing winds and building seas near the Revillagigedo Islands in association with a developing low. High pressure across the eastern slopes of the Sierra Madre Mountains in Mexico continues to induce strong northerly gap winds across the Gulf of Tehuantepec. The strong winds over the Gulf of Tehuantepec will pulse to near gale force during the overnight and early morning hours the next few days. Model guidance indicates winds will further increase to minimal gale force Monday night through early Wednesday morning as high pressure builds behind a front moving into the Gulf of Mexico. Seas downstream from the gulf will build to 8-11 ft during the times of maximum winds through Monday. Maximum seas of 12-14 ft are expected with the gale force winds. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh offshore winds will develop across the Papagayo region Sat and continue through Mon with seas of 5-6 ft. Light and variable winds and seas of 4 to 5 ft seas prevail N of 09N, with little change expected through Saturday morning. Seas will increase slightly through the weekend as cross-equatorial SW swell reaches the region. Gentle to moderate SW to W winds and 5 to 6 ft seas are currently observed across the area S of 09N, with a slight increase in seas expected through the weekend with the arrival of SW swell. REMAINDER OF THE AREA... Unusually strong high pressure centered NW of the area near 43N146W extends a ridge southeast to near 20N115W. The pressure gradient between the ridge and the monsoon trough is producing an area of fresh to strong NE winds north of 22N west of 125W, with moderate to fresh NE winds from 13N-22N W of 130W. Seas of 9-13 ft with a northerly swell component are noted across the N waters N of 24N W of 125W based of altimeter data. Winds are forecast to diminish across the northern forecast waters on Saturday as the strong high moves SE and weakens slightly. Seas will gradually subside, but 8-9 ft seas will continue to affect much of the area N of 20N W of 120W by Sat evening. In addition, large swell from the S Hemisphere will continue to propagate across the south-central waters, particularly S of 12N between 105W-115W during the next couple of days. $$ GR