000 AXPZ20 KNHC 251540 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sun Sep 25 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... At 25/1200 UTC...shower and thunderstorm activity associated with a low pressure system located near 15.2N 119.7W or about 715 nm southwest of the southern tip of the Baja California peninsula has become a little better organized overnight. Satellite imagery also suggests that the circulation is gradually becoming better defined, with a cluster of moderate to strong convection within about 150 nm SW of low center. Scattered moderate convection is also noted to the NE of the center, particularly from 14.5N-17.5N between 115W-119W. Environmental conditions are conducive for additional development, and a tropical depression is likely to form later today or tonight while the system moves slowly northward. A gale warning is already in effect in association with this feature beginning this evening. Based on the computer models... this system could reach tropical storm force on Monday. Please refer to the latest Graphical Tropical Weather Outlook for more information at http://hurricanes.gov. ...TROPICAL WAVES... A tropical wave is located to the N of 08N along 97W. Scattered moderate isolated strong convection is observed on either side of the wave axis, and where the wave meets the monsoon trough, but mainly N of 12N...including the Gulf of Tehuantepec between 93W- 96W...and from 08N-10N between 93W-102W. Expect the wave to gradually lose identity over the next few days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends across the far SW Caribbean and northern Costa Rica in to EPAC along 10N86W to 11N97W to 09N110W, then it resumes just SW of the surface low located near 15.2N 119.7W, and continues along 12N130W to a 1010 mb low pressure near 12N137.5W. Scattered moderate convection is noted from 08N- 10N between 93W-102W...from 09N-11N between 123W-128W, and from 10N-13.5N W of 130W. A cluster of moderate to isolated strong convection has developed south of the Azuero peninsula, within about 60 nm of 05N81W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... mainly light to gentle winds are noted north of 20N between the subtropical ridge to the west and weak trough over the Gulf of California. Northerly swell to 8 ft persist off Baja California Norte per the most recent altimeter pass, particularly N of 27N between 120W-125W, but will be decaying to below 8 ft late today. Building high pressure over the Great Basin to the north of the region will allow a brief surge of fresh to strong northerly winds into the northern Gulf of California this afternoon, diminishing to 20 kt tonight, then veering more east to southeast on Monday on the tail end of a weak frontal boundary drifting into northern Mexico. 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 Tuesday night 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 north of the monsoon trough while gentle to locally moderate south to southwest flow is expected south of monsoon trough the middle of the week. Combined seas of 3-6 ft, primarily in long-period southwest swell, are expected through the middle of the week. REMAINDER OF THE AREA... An area of low pressure located near 12N137.5W or about 1105 nm east-southeast of the Big Island of Hawaii continues to produce disorganized showers and thunderstorms. Satellite imagery indicates scattered moderate convection from 10N-14N between 135W-140W. Currently, convection is limited near the low's center. Any development of this disturbance should be slow to occur during the next couple of days. After that time, environmental conditions could become more conducive for development. This system is expected to move west-northwestward during the next couple of days, and then turn northward as it approaches the Central Pacific basin. The pressure gradient between this low and the subtropical ridge to the north is resulting in an area of fresh to strong northeast from 13N-22N W of 130W. An earlier altimeter pass provided observations of combined seas of 8 to 12 ft within the area of the trade winds. This marine conditions will diminish in areal extent, covering the waters from 13N to 17n between 135W and 140W by this evening. Seas of 8 to 9 ft will persist from 12N to 16N west of 138W through early Monday morning, just north of the low pressure. $$ GR