000 AXPZ20 KNHC 231604 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURES... A broad and elongated area of low pressure continues within the monsoon trough and is analyzed as a 1007 mb low pressure near 12N116W, and has changed little during the past several hours. Latest satellite imagery shows scattered strong convection from 10N to 12N between 110W and 115W, and from 11N to 14N between 116W and 120W. The pressure gradient is supporting strong south to southwest winds mainly to the east 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 area 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 are expected to become favorable for tropical cyclone formation through the next 48 hours. Even if it takes longer for convection to band, the pressure gradient should tighten with minimal gale winds developing early Saturday afternoon with the low forecast near 15N116W. The low is forecast to move north-northwest reaching near 16N116W late Sat night with seas gradually building up to maximum of about 16 ft. There is plenty of uncertainty in the future exact track and intensity of this system. 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 93W. It is moving w at 10 to 15 kt. Scattered moderate to strong convection is seen within 60 nm of a line from 12N88W to 13N91W to 14N93W. Scattered moderate to isolated strong convection exists from 11N to 15N between 93W and 97W, and within 60 nm of 13N102W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends w off the Pacific coast of Costa Rica at 10N86W to 11N93W to 09N98W to 11N104W where it loses identity. Latest available scatterometer winds indicated that the monsoon trough resumes west of the low near 12N116W to 12N122W to low pressure near 13N128W 1010 mb to 10N133W to 11N140W. Scattered moderate convection is within 120 south of the axis between 98W and 102W, and also within 60 nm of the axis between 122W and 125W. ...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. An Ascat pass from 0538Z last night revealed strong nw winds from 30N to 36N between 118W and 121W, with seas of 8 to 11 ft. Moderate to fresh northwest winds are observed elsewhere within 250 nm w of the Baja Peninsula. The pressure gradient is forecast to relax this afternoon, with moderate nw flow expected west of the Baja Peninsula by early Sat along with seas in the range of 5 to 8 ft. The highest of these seas is expected to the north of 27N. The gradient should further relax with gentle north winds expected west of the Baja California by late Sun. An upper level low moving slowly westward is just to the northwest of Cabo Corrientes. Ample moisture and instability associated with this low is bringing scattered showers and thunderstorms within 180 nm of the coast of Mexico from Manzanillo to Cabo Corrientes. Similar activity, mainly related to previous nocturnal convection, is seen weakening within 30 nm of 23n107W. The activity with the upper low is expected to continue through tonight, and into Saturday. The typical thermal trough over the northern Baja Peninsula, and northern Gulf of California will move southeast 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. Light and variable winds expected elsewhere along the Pacific primarily to mixing long period s and nw swell. Uncertainty with respect to winds and seas comes into to late in the weekend, and into next week as the tropical low previously described, moves north-northeast towards the general direction of far southern Baja California by Sunday night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light east to southeast winds are expected n of about 12N while gentle to locally moderate south to southwest flow is 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 southwest and northwest swell, then begin to subside to 4 to 6 ft beginning on Sat. REMAINDER OF THE AREA... A 1010 mb low pressure area is analyzed along the monsoon trough near 13N128W. Scattered strong convection is within 120 nm of the low in the northwest quadrant. Scattered moderate to isolated strong convection is within 30 nm of 11N130W. The low is forecast to reach near 12N134W by early on Saturday, and to near 12N138W on Sunday. The pressure gradient will tighten between the broad low pressure along the monsoon trough and the subtropical ridge to the north with fresh northeast trades developing tonight, and combined seas building to 6 to 9 ft across the discussion waters roughly from 13N to 25N west of 130W through Sunday. $$ AGUIRRE