000 AXPZ20 KNHC 240945 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0945 UTC. ...SPECIAL FEATURES... A broad and elongated area of low pressure continues within the monsoon trough and is analyzed as 1007 mb low pressure at 12.5N118W. Scattered moderate isolated strong convection is observed within 120 nm either side of a line from 11N117W to 15N120W where banding features appear to be developing. The pressure gradient is supporting strong s to sw winds e of the low center, within 120 nm either side of a line from 15N110W to 09N116W with seas of 8 to 11 ft. Atmospheric and oceanic conditions are favorable for tropical cyclone formation over the next several days. Even if it takes longer for the convection to organize into persistent bands, the pressure gradient should tighten with minimal gale winds developing on Sat night with the low forecast near 16.5N116.5W. The low is forecast to move n reaching near 18N117W on Sun night with seas gradually building to about 15 ft. There will be plenty of uncertainty in the intensity and track organization occurs. 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 96W, and has been progressing w at about 12 kt. Isolated moderate and strong convection is observed within about 150 nm either side of the wave axis. Expect the wave to gradually lose identity over the next few days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends sw off the Pacific coast at the Nicaragua and El Salvador border at 13N88W to 10N100W to 13N107W where it loses identity. Scatterometer winds indicate that the monsoon trough resumes just w of the surface low at 12N118W, and continues w through a 1009 mb surface low at 12N130W and continues w to beyond 10N140W. Scattered moderate isolated strong convection is observed well nw of the low pressure at 12N130W, roughly within 75 nm either side of a line from 15N129W to 13N135W. Similar convection is observed within 120 nm either side of a line from 10N91W to 11N103W, within 30 nm either side of a line from 17N99W to 12N102W and elsewhere within 180 nm either side of a line from 14N109W to 11N130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sub-tropical ridge axis extends from nw to se across the offshore zones w of the Baja Peninsula terminating at a fairly sharp crest near 21N110W. Strong nw winds are observed from 30N to 32N between 118W and 123W, with seas of 7 to 10 ft. Moderate to fresh nw winds are observed elsewhere n of 24N within 250 nm w of the Baja Peninsula with gentle n winds noted to the s of 24N. The pressure gradient is forecast to quickly relax today with gentle nw to n flow expected w of the Baja Peninsula through the remainder of the weekend. A trough is barely noticeable across the southern Gulf of California with moderate to locally fresh n winds across the gulf waters n of 28N and light southerly winds s of 28N. Expect strong n winds to develop across the gulf waters n of 30N late tonight and persist through Sun night. Light and variable winds expected elsewhere along the Pacific coast of Mexico primarily to mixing long period s and nw swell. Uncertainty then increases as the tropical low previously described, moves northward and begins to affect offshore PMZ015 tonight, initially to the s of 19N between 112W and 116W, with the conditions deteriorating on Sun and Mon as the gale center, or tropical cyclone, continues n across the offshore waters w of the southern Baja Peninsula. Plenty of uncertainty, so expect fluctuations in track and intensity forecasts for the next few days. Guidance is hinting at a fairly strong cold front reaching the sw Gulf of Mexico on Tue, and reinforced on Wed, resulting in strong to near gale flow across the Gulf of Tehuantepec on Wed night and continuing into Fri. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle e to se winds expected n of about 12N while gentle to locally moderate s to sw flow is expected s of 12N through the middle of the next week. Combined seas of 4 to 7 ft will continue today primarily in mixing long-period sw and nw swell, then subside to 3 to 5 ft on Sun and continuing into the middle of next week. REMAINDER OF THE AREA... A 1009 mb low pressure area is analyzed along the monsoon trough near 12N130W. Expect the low to move wnw to near 13N140W late Sun. The pressure gradient between this low and the subtropical ridge to the n will maintain fresh to strong ne trades, and combined seas of 6 to 9 ft, across the discussion waters from 13N to 25N between 130W and 140W today, with these conditions gradually diminishing/subsiding from the ne to 20 kt or less, and seas less than 8 ft on Mon. $$ Nelson