546 AXPZ20 KNHC 232204 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Jul 23 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 2145 UTC. ...TROPICAL WAVES... A low-latitude tropical wave has its axis along 88W from 03N to 13N, moving westward around 20 kt. The wave remains evident in tropical wave model diagnostics as well as a maximum in total precipitable water satellite imagery. Scattered moderate is within 60 nm either side of the axis from 10N-12N, and within 120 nm west of the wave from 06N-09N. A tropical wave has its axis extending from 03N100W to 10N99W to 16N98W, moving westward at an estimated speed of 18 kt. The wave is evident in 700 mb model guidance streamlines as well as a pronounced maximum in total precipitable water satellite imagery. Numerous strong convection is within 30 nm of 15N100W. Scattered moderate isolated strong convection is within 120 nm west of the wave from 09N-12N. A tropical wave has its axis extending from 04N127W to a 1011 mb low near 12N129W and to 17N128.5W, moving westward at 15-20 kt. The wave is associated with broad troughing at 700 mb as depicted in model guidance. The low along this wave is rather compact in size as observed in satellite imagery. Scattered moderate isolated strong convection is seen within 120 nm of the low in the SW quadrant. The 1736 Ascat pass revealed fresh to strong winds within 120 nm of the low in the N quadrant and within 60 nm of the low in the SE quadrant. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1009 mb low over NW Colombia near 09N74W to Costa Rica near 10N83W to 09N90W to 12N118W to a 1011 mb low near 12N129W and west of the area at 11N140W. Aside from convection associated with the tropical waves, scattered strong convection is within 60 nm north of the axis between 119W-121W. Scattered moderate convection is within 60 nm of the axis between 110W-113W, and also south of the axis within 60 nm of a line from 08N115W to 08N119W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad and weak high pres ridge extends From 32N140W east- southeastward to the Revillagigedo Islands near 16N107W. The ridge is maintaining light to moderate NW winds across the Mexican offshore waters, except for the Gulf of Tehuantepec area as discussed below. Little change is expected in these conditions during the next several days. A long period SW cross-equatorial swell is affecting the waters S of 20N. This extensive swell event will continue spreading northward, and will cause seas to build to the range of 7 to 9 ft in the open waters for all the forecast zones through Tue night before they begin to slowly subside through the rest of the week. Gulf of Tehuantepec: The earlier occurrence of fresh to strong north winds through the gap area have diminished to the light to moderate range this afternoon. These winds will become gentle south to southwest in direction tonight and then gentle to variable on Tue. Wind waves generated by the north winds are interacting with the SW swell event resulting in mixed seas to the south of the Gulf, with sea heights ranging between 8-9 ft. These seas will merge with the much larger area of 8 ft seas approaching from the tonight, and gradually subside Tue and Wed. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong northeast to east winds will pulse during the late night and morning hours through Wed morning before diminishing to fresh intensity. Ship with call sign "DDVK2" reported northeast winds of 25 kt at just after 12Z this morning near 11N89W. Seas from these winds are interacting with the southwest swell event resulting in mixed seas in the gulf as high as high as 9 ft through tonight before beginning slowly subside on Tue. Gentle to moderate northeast to east winds are forecast elsewhere N of the monsoon trough which will meander west of Central America between 07N and 10N. Moderate to fresh S to SW winds are generally expected S of the trough axis during the next several days. A long-period SW cross-equatorial swell event encompasses just about the entire region. Maximum wave heights with this event are near 10 ft south of 06N between 82W-90W. Wave model guidances suggest that seas will gradually subside to 8 ft Wed, and to less than 8 ft Thu. REMAINDER OF THE AREA... A weak surface ridge extends into the discussion area at 32N140W, and continues east-southeastward to 25N118W and to the Revillagigedo Islands near 16N107W. The gradient between the ridge and lower pressure found along and near the monsoon trough is maintaining mainly fresh northeast to east trade winds north of the monsoon trough, south of 20N and west of 115W. Little change in this pattern is expected for the upcoming week. Swell generated by strong winds north of the area is propagating southward inducing seas to build to 8 ft in the discussion waters N of 28N and W of 133W. This swell will decay through this evening allowing for seas to subside to less than 8 ft. Low pressure of 1010 mb is located near 12N along the tropical wave that extends from 04N127W to 17N128.5W. The low will generate fresh to strong winds over the waters within 180 nm to its north and within 60 nm to its southeast as it tracks in a westward to west-northwestward motion reaching near 11N139W by early Wed afternoon and cross 140W soon afterwards. Seas in the range of 8-10 ft are expected with its associated winds. Lingering mixed swell will produce seas of 8-9 ft over the far western waters on Tue, however, these conditions will be overtaken by an extensive area of cross-equatorial southwest swell as stated below. Large long-period SW swell is crossing the equator, with seas of 8 to 11 ft affecting almost all of the waters S of 20N as confirmed by satellite-derived sea height data this afternoon. Wave model guidances indicate that the swell will slowly dissipate through Wed allowing for seas to subside to 8 ft or less. $$ Aguirre