048 AXPZ20 KNHC 202154 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Fri Jul 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 1800 UTC surface analysis and satellite imagery through 1500 UTC. ...TROPICAL WAVES... A tropical wave is analyzed from 07N to 17N near 108W moving W around 20 kt. The wave is diagnosed from the 700 mb tropical trough diagnostics as well as a maximum in total precipitable water west of the trough axis. Scattered moderate convection is noted from 07N to 14N between 105W and 110W. This system has a moderate chance of developing into a tropical cyclone during the next five days. A tropical wave is analyzed from 05N to 13N near 116W moving W around 20 kt. The wave is weak, but can be tracked via the 700 mb tropical trough diagnostics. Scattered moderate convection is noted within 60 nm of the axis south of 09N. A tropical wave is analyzed from 12N to 22N near 137W moving W around 20 kt. The wave helped initiate a surface low of 1012 mb at 13N131W along the monsoon trough. This low has become more well-defined as seen from the 1837 UTC ASCAT scatterometer pass showing a closed low with peak winds of strong breeze about 180 nm NE of the center. The wave remains well-defined at 700 mb, ahead of the surface low. The ECMWF model better initializes this complex situation compared with the GFS today. Scattered moderate and isolated strong convection is occurring within 180 nm of the low's center. This system has only a low chance of developing into a tropical cyclone during the next five days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from a weak 1007 mb low over coastal Colombia near 09N76W into the Pacific near 08N78W to 10N95W to 08N110W to a 1012 mb low near 13N131W to 13N140W. Scattered moderate and isolated strong convection is noted within 180 nm of the trough from Central America to 122W. Scattered moderate and isolated strong convection is occurring within 180 nm of the low's center. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface ridge is in place from 32N138W to the Revillagigedo Islands maintaining winds of only fresh breeze or weaker across the Mexican offshore waters. Little change is expected for the next several days. A long-period southwesterly cross-equatorial swell is moving into the region today, allowing seas to build to 9 ft in open waters through early next week. In the Gulf of Tehuantepec, pulses of strong northerly gap winds will occur during late night and morning hours through Mon morning before fading on Tue. Wind waves from these northerly winds will interact with the SW swell event to produce mixed seas south of the Gulf up to 9 ft by Mon before fading on Tue. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong easterly winds during late night and morning hours are expected into early next week. Seas from these easterly winds will interact with the SW swell event to produce mixed seas southwest of the Gulf up to 10 ft by Mon before fading on Tue. Easterly winds of only fresh breeze or weaker are forecast elsewhere N of the monsoon trough which will meander west of Central America between 07N and 10N. Southerly winds of only fresh breeze or weaker are expected S of the trough axis the next few days. A long-period southwesterly cross-equatorial swell is moving into the region today, allowing seas to build to 9 ft in open waters through early next week. An altimeter pass at 1800 UTC along 90W showed peak seas of 8 to 9 ft near the equator. REMAINDER OF THE AREA... A surface ridge is in place from 32N138W to the Revillagigedo Islands maintaining tradewinds of only fresh breeze or weaker across the high seas. Little change is expected. See discussion above regarding the tropical wave near 108W. Large long period southwesterly swell is moving across the equator between 90W and 130W, and will continue to propagate northward, affecting most of the area east of 130W before fading on Tue. An altimeter pass at 1940 UTC along 115W showed peak seas of 11 ft near the equator, dropping below 8 ft by 10N. $$ Landsea