000 AXPZ20 KNHC 260235 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 154 UTC Mon Sep 26 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 0000 UTC surface analysis and satellite imagery through 0230 UTC. ...SPECIAL FEATURES... Tropical Depression Eighteen-E is near 16.7N 120.1W at 26/0230Z or about 660 nm southwest of the southern tip of the Baja California peninsula, moving north-northwest at 6 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 30 kt with gusts 40 kt. Scattered moderate showers and thunderstorms are active within 210 nm of the southeast semicircle of the center of T.D. Eighteen-E. The depression is forecast to intensify to tropical storm strength overnight and move within 180 nm to the west of Clarion Island Monday night before weakening. See latest NHC forecast/advisory under AWIPS/WMO headers WTPZ23 KNHC/TCMEP3 or visit the NHC website at http://hurricanes.gov for more details . ...TROPICAL WAVES... A tropical wave is located to the north of 09N along 97W/98W drifting west. A weak surface low pressure area may be starting to develop along the monsoon trough in the vicinity of the tropical wave. Another area of showers and thunderstorms has persisted over western Panama and Costa Rica and the adjacent Pacific waters over the past couple of days, propagating slowly westward. Specifically, scattered moderate to isolated strong convection is noted north of 05N between 82W and 86W off western Panama and southwest Costa Rica. This may be evidence of another tropical wave moving from the southwest Caribbean into the eastern Pacific. Unlike the previous tropical wave, this tropical wave would be fairly low latitude and is probably better defined in the lower to mid levels of the atmosphere than at the surface. The main impact will be persistent scattered to numerous showers and thunderstorms over the next couple of days mainly east of 80W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N86W to 10N112W. It resumes at 14N123W to 12N125W to 1011 mb low pressure near 12N139W to beyond 11N140W. Scattered moderate convection is within 60 nm south of the monsoon trough axis between 92W and 100W and within 120 nm south of axis between 135W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... The pressure gradient between relatively low pressure over southern Arizona and northwest Sonora compared to strong high pressure farther north over the Great Basin is contributing to the potential for fresh eastern winds across the far northern Gulf of California from late tonight through Monday, locally reaching 25 kt at times. Wave height development will be limited by fetch however, and winds will diminish by late Monday. Elsewhere winds and seas will remain fairly limited across the region through mid week, except in areas beyond 200 nm off Baja California Sur that will be impacted by increased winds and seas by mid week on the periphery of the by then weakening T.D. Eighteen-E, tracking mainly just outside of the offshore waters zones. Farther south, a cold front is forecast to move across the Gulf of Mexico waters early in the week. High pressure behind the front will likely induce the first Gulf of Tehuantepec gap wind event of the season with fairly weak pulse Tuesday night into Wednesday morning followed by a strong pulse Wednesday night into Thursday morning. At this time, marine guidance suggests northerly winds of 20-25 kt and building seas to 8 ft by early Thursday. 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 12N139W or about 1100 nm east-southeast of the Big Island of Hawaii continues to produce disorganized showers and thunderstorms. Satellite imagery indicates scattered moderate convection within 90 nm in the southeast quadrant of the center of the low pressure. 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. Persistent northeast swell is allow combined seas to 9 ft north of the low pressure, from 13N to 17N west of 138W. $$ CHRISTENSEN