000 AXPZ20 KNHC 120946 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Sep 12 2017 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... Tropical Depression 15-E centered at 15.8N 115.1W at 0900 UTC moving W or 260 degrees at 13 knots. The minimum central pressure is estimated 1006 mb. The maximum sustained winds are 20 to 25 kt with gusts to 35 kt mainly over the NW semicircle. Scattered moderate isolated strong convection is currently observed 210 nm over the W quadrant of the depression. The depression is forecast to move W and weaken to a remnant low in a couple of days. For additional information refer to NHC forecast advisories under WMO/AWIPS headers WTPZ25 KNHC/MIATCMEP5. A surface low is forecast to develop along the monsoon trough near 14N104W this afternoon, and move to near 15N104W tonight, with possible tropical cyclone development. Another surface low is forecast to develop further W along the monsoon trough near 17N109W on Thu, and move NE with the two lows, or possibly tropical cyclones, merging near 20N107W on Fri. Strong southerly flow, with 8-12 ft seas, is forecast initially SE of the lows and monsoon trough axis, roughly within the area from 07N-12N between 101W-113W. By Wed night, expect strong to near gale force winds within 120 nm of a line from 18N103W to 12N111W with seas conservatively building to 10-15 FT. This merged tropical low, or possible tropical cyclone, will then continue N across the central Mexican offshore waters reaching near the entrance to the Gulf of California on Sat accompanied by at least near gale force winds and seas conservatively to 20 ft. ...TROPICAL WAVES AND TROPICAL LOWS... A 1010 mb low is embedded in the monsoon trough at 11N134W with isolated moderate to strong convection is observed within 30 nm of the low. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends WNW off the coast of Nicaragua at 13N87W to 14N95W to 13N110W, then turns NW through Tropical Depression 15-E, then turns SW to 13N121W, then W to 12N135W, then Sw to beyond 10N140W. Scattered moderate isolated strong convection is noted E of 81W and within 240 nm either side of a line from 12N90W to 13N102W to 10N130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A NW to SE oriented trough will meander E to W across the Baja California Peninsula and the Gulf of California with a surface low developing intermittently along the trough axis over the far northern Gulf waters, and perhaps also over the central Gulf of California. A W to E orientated ridge will meander from 23N116W to 21N110W through the middle of the week, with a moderate W to NW breeze forecast across the EPAC waters S and W of the Baja California Peninsula through Thu night, with 5 to 6 ft seas. Gulf of California...Light, mostly NW winds expected through Wed. Gulf of Tehuantepec: Strong to near gale force northerly flow is expected through sunrise this morning, with seas building to 12 ft downstream of the gulf waters near 14.5N95.5W. Only moderate noctural drainage flow forecast tonight. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to locally fresh southwesterly monsoonal flow expected this week. Combined seas are currently 6 to 8 ft primarily due to cross-equatorial swell that is forecast to subside today with seas forecast less than 8 ft tonight. REMAINDER OF THE AREA... See special features paragraph. A ridge extends from 32N138W to 23N116W with light to locally moderate anticyclonic flow expected elsewhere N of the monsoon trough and W of 115W through the middle of the week. $$ Nelson