000 AXPZ20 KNHC 241536 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sat Sep 24 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 large low pressure area, analyzed as a 1007 mb low pressure near 13N118W on the 1200 UTC surface map, is producing disorganized shower and thunderstorm activity. Satellite images indicate that the low's circulation, although still broad, is gradually becoming better defined, and a band of moderate to isolated strong convection is seen within about 90 nm of a line from 13N117W to 12N120W to 14N120W. Currently, the pressure gradient is supporting strong S to SW winds within 120 nm SE semicircle of low center with seas of 8 to 9 ft. Environmental conditions are conducive for a tropical depression to form during the next day or two. This disturbance is expected to move slowly northward during the next few days. A gale warning is already in effect in association with this feature beginning on Sunday morning. Please refer to the latest Graphical Tropical Weather Outlook for more information at http://hurricanes.gov. ...TROPICAL WAVES... A tropical wave is analyzed N of 10N along 95W. The axis crosses the Gulf of Tehuantepec. Scattered moderate to isolated strong convection is noted on either side of the wave axis mainly N of 13N between 91W and 99W. Expect the wave to gradually lose identity over the next few days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends across parts of Panama and southern Costa Rica from 09N79W to 09N85W to 11N95W to 10N107W...then it resumes at 12N119W to 1009 MB low pressure located near 12N132W to 10N140W. Scattered moderate convection can be found from 08N to 12N between 91W and 98W...and from 09N to 11N between 127W and 131W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sub-tropical ridge extends from NW to SE across the offshore zones W of the Baja Peninsula to near 21N115W producing mainly gentle to moderate NW winds. Seas of 8 to 10 ft in NW swell are noted per an altimeter pass within this area. Moderate to locally fresh NW winds are observed based on scatterometer data between Punta Eugenia and Cabo San Lazaro. The pressure gradient is forecast to quickly relax today with gentle NW to N flow expected W of the Baja California Peninsula through the remainder of the weekend. Scatterometer data also show gentle to moderate NW winds across the N part of the Gulf of California particularly N of 30N. Winds are forecast to increase to 20-25 kt across the gulf waters N of 30N by late Sunday as a moderate to strong high pressure builds across the Great Basin. A cold front is forecast to move across the Gulf of Mexico waters. High pressure behind the front will likely induce the first Gulf of Tehuantepec gap wind event of the season by late Tuesday into Wednesday morning. At this time, marine guidance suggests Northerly winds of 20-25 kt and building seas to 8 ft. Winds will further increase to 25-30 kt Wednesday night into Thursday morning with seas up to 9-10 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Mainly light and variable winds are noted N of the monsoon trough while gentle to locally moderate S to SW flow is expected S of monsoon trough through early next week. Combined seas of 4 to 7 ft will continue today primarily in long-period SW swell, then subside to 4 to 5 ft late on Sun and continuing into early next week. REMAINDER OF THE AREA... A 1009 mb low pressure area is analyzed along the monsoon trough near 12N132W. Expect the low to likely reach 140W on Monday, then will remain near 140W through mid-week. The pressure gradient between this low and the subtropical ridge to the N is resulting in an area of fresh to strong NE trades, and combined seas of 6 to 9 ft, across the discussion waters from 17N to 26N W of 130W. These marine conditions area forecast to gradually diminish in about 24 hours as high pressure located N of area near 34N137W moves NE to a position near 40N133W by Sunday morning. $$ GR