923 AXPZ20 KNHC 172131 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2130 UTC Tue Jul 17 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...TROPICAL WAVES... A tropical wave is extends across the southwest Caribbean into the eastern Pacific south of eastern Panama, moving W at 10 to 15 kt. Scattered moderate convection is noted from 05N to 07.5N between 80W and 85W. A tropical wave is analyzed from 05N92W to 13N95W moving W at 10 to 15 kt. No significant convection is observed with this wave. A tropical wave is analyzed from 05N to 14N near 110W. The convection in the area of the tropical wave earlier in the day has since dissipated. A tropical wave is analyzed from 09N123W through a 1009 mb surface low embedded along the wave at 14N123W to 17N122W. This system is moving W at 10 to 15 kt. Scattered moderate convection is observed from 14N to 17N between 119W to 123W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N78W to 08N95W. The ITCZ continues from 08N95W to the tropical wave near 110W, then on to 10N115W. The ITCZ continues from 10N125W to beyond 10N140W. Scattered moderate convection is noted within 120 nm either side of the ITCZ between 90W and 105W, and within 120 nm of the ITCZ west of 125W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A scatterometer pass from this morning along with earlier reports from Salina Cruz on the coast of Mexico near the Gulf of Tehuantepec indicated ongoing fresh to strong drainage flow into the Gulf of Tehuantepec. This has likely temporarily diminished as overnight drainage effects have weakened. The gap flow was being enhanced between high pressure over the western Gulf of Mexico and a tropical wave passing westward south of the region, and strong nocturnal winds with seas to 7 ft are expected into Thu morning. Light to gentle breezes and minimal seas are noted elsewhere over Mexican offshore waters. , with seas observed at 8 ftver the mountainous terrain Divergent flow aloft associated with a mid to upper low over northwest Mexico was supporting scattered overnight showers and thunderstorms inland over the mountainous terrain east of the Gulf of California. Some of this activity was impacting the southern Gulf of California but is now dissipating. This may repeat again tonight, but taper off early as the mid/upper low migrates through the region. Looking ahead, long period southwest swell will propagate into the Mexican offshore waters by Fri, with combined seas in open waters building in excess of 5 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Strong nocturnal drainage flow, accompanied by 6 to 8 ft seas, are expected through Thu night with extended guidance suggesting these conditions will resume on Sun night. Gentle to occasionally moderate E winds are forecast elsewhere N of the monsoon trough which is meandering between 07N and 10N. Moderate southerly winds are forecast S of the monsoon trough for the next several days accompanied by 4 to 6 ft seas. Long period southerly swell, in the form of 7 to 8 ft seas, will pass north of the Equator by Thu, and propagate northward into the offshore waters of Central America through Sat. REMAINDER OF THE AREA... A broad upper low is centered near 21N127W, supporting an associated 1009 mb surface low near 14N123W along a tropical wave. While upper winds are unfavorable for further development, recent scatterometer data confirms fresh to strong easterly flow in a swath on the northern side of the surface low through. Concurrent altimeter data shows seas reaching up to 9 ft. The tropical wave will continue west, reaching 130W by Thu, with the low gradually dampening out as the upper lift north of the area, allowing winds and seas to diminish. The subtropical ridge will build north of 20N, supporting moderate to fresh trade winds from 08N to 15N west of 130W by late week. Long period cross-equatorial swell, in the form of 7-9 ft seas, will move across the Equator between 90W and 125W on Wed, and continue to propagate N across the discussion area through Sat. $$ Christensen