000 AXPZ20 KNHC 230944 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Fri Sep 23 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 11.5N115W. Scattered moderate isolated strong convection is observed within 240 nm either side of a line from 10N108W to 14N116W. The pressure gradient is supporting strong s to sw winds mainly e of the low center within 120 nm either side of a line from 12N113W to 09N113W to 08N115W with seas of 8 to 12 ft. This ares is surrounded by a larger area of fresh winds with seas of 7 to 10 ft in mixing SW and NW swell, roughly from 07N to 14N between 107W and 117W. Atmospheric conditions will become favorable for tropical cyclone formation over the next several days. Even if it takes longer for convection to band, the pressure gradient should tighten with minimal gale winds developing on Fri night with the low forecast near 14.5N114.5W. The low is forecast to move n-nw reaching near 16.5N114.W on Sat night with seas gradually building to about 16 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 91W and has been progressing w at about 12 kt. Scattered moderate isolated strong convection is observed within 45 nm either side of a line from 13N91W to 15N94W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends w off the Pacific coast of Costa Rica at 10N86W to 10N102W where it loses identity. Scatterometer winds indicate that the monsoon trough resumes w of the surface low at 11.5N115W. Isolated moderate and strong convection is observed within 180 nm over the w semicircle of the low pres at 13N128W and elsewhere within 240 nm either side of lines from 05N78W to 17N109W, and from 12N117W to 14N125W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sub-tropical ridge axis extends from nw to se across the western portion of the offshore zones w of the Baja Peninsula with a fairly sharp crest near 21N110W. Strong nw winds are observed from 30N to 32N between 118W and 121W, with seas of 7 to 10 ft. Moderate to fresh nw winds are observed elsewhere within 250 nm w of the Baja Peninsula. The pressure gradient is forecast to relax today with moderate nw flow expected w of the Baja Peninsula by early Sat, with 5 to 8 ft seas, highest seas n of 27N. The gradient should further relax with gentle n winds expected w of Baja by late Sun. A thermal trough over the northern Baja Peninsula, and northern Gulf of California will move se over the southern portion of the area early Sat. Gentle southerly flow across the Gulf of California today will clock to the n-nw behind the trough, and increase to moderate to fresh with seas building to perhaps as high as 5 ft in the exposed far northern waters tonight. Little change then expected until late Tue when the gradient will relax with winds becoming light and variable across the Gulf of California. Light and variable winds expected elsewhere along the Pacific 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 late Sat, 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-ne reaching the Baja Peninsula in the general time frame of Tue. 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 through next Fri. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light e to se winds expected n of about 12N while gentle to locally moderate s to sw flow expected s of 12N through the middle of the next week. Combined seas of 4 to 7 ft will continue through tonight primarily in mixing long-period sw and nw swell, then subsiding to 3 to 6 ft on Sat through Mon, with 3 to 5 ft seas expected on Tue. REMAINDER OF THE AREA... A 1010 mb low pressure area is analyzed along the monsoon trough near 13N128W. Isolated moderate and strong convection is currently noted within 180 nm over the w semicircle of the center. Expected the low to move w to near 12N132W tonight and near 12N136W on Sat night. The pressure gradient will tighten between the broad low pressure along the monsoon trough and the subtropical ridge to the n with fresh ne trades developing tonight, and combined seas building to 6 to 9 ft across the discussion waters from 13N to 25N between 130W and 140W late tonight, and then gradually subsiding to less than 8 ft on Mon. $$ Nelson