968 AXPZ20 KNHC 201556 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Aug 20 2018 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. ...TROPICAL WAVES... A tropical wave along 90W-91W is moving W near 20 kt. Satellite imagery suggests two short amplitude waves are moving through this region between 86W and 96W and reorganizing. Scattered moderate to strong convection along the monsoon trough described below, and from 11N to the Mexican coast between 87.5W and 96.5W. A tropical wave along 111W-112W is moving W around 15 kt. Significant convection currently with this wave is confined near the monsoon trough and described below. A tropical wave along 129W is moving W around 15 kt. Scattered moderate to strong convection is found from 13N to 17.5N between 121W and 136W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from low pres 1010 mb near 09N74W and meanders WNW to near 12N123W where it terminates. The ITCZ extends from 12N129W to beyond 11N140W. Widely scattered moderate to strong convection is seen within 180 nm N and 240 nm S of the monsoon trough between 84W and 122W. Scattered moderate to strong convection is within 45 nm N and 150 nm S of the ITCZ between 130W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weak surface ridge across the NE Pacific is centered on a 1030 nm high near 46N137W and extends S and SE, entering the forecast waters near 30N130W, then extends SE to just beyond the Revillagigedo Islands. This ridge will support gentle to moderate NW winds across the offshore waters of Baja California through Wed before the ridge strengthens modestly and the pressure gradient tightens across Baja California Norte Thu and Fri. Seas will generally remain in the 4-5 ft range through Wed. Surface troughing over the Baja Peninsula will maintain a light wind regime over the Gulf of California through Fri night, and allow for afternoon sea breezes and nocturnal land breezes to dominate. Strong N to NE gap winds will affect the Gulf of Tehuantepec Tue night through Thu night, and forecast to peak near 30 kt late Wed night. Seas of 4 to 6 ft during the daytime could build to 8 ft each of these nights and 8-10 ft late Wed night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough will linger near 09N during the next few days. Winds on both sides of the trough axis will generally be light to moderate. The main exception to this will be over the Gulf of Papagayo, where moderate to fresh offshore winds will pulse to locally strong each night. Seas are expected to remain below 8 ft downstream of Papagayo during this time. REMAINDER OF THE AREA... Hurricane Lane continues moving farther away into the Central Pacific. The area of seas above 8 ft generated by mixed swell in the vicinity of Lane moved to the W of 140W earlier this morning. Elsewhere, the pressure gradient between ridging across the northern waters and the ITCZ will support gentle to moderate trades and 4-7 ft seas in mixed swell N of the ITCZ and W of 120W through the middle of this week. Sea heights will be relatively low for most of the forecast area this week. Mixed SE and SW swell will caused seas S of 02S and W of 105W to briefly build to 8 ft this morning and will continue later through Tue morning before subsiding less than 8 ft. A much more robust round of long period swell could arrive from the Southern Hemisphere toward the end of this week and cause seas near the Equator to begin building on Sat. $$ Stripling