976 AXPZ20 KNHC 240403 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 141 UTC Tue Jul 24 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 0000 UTC surface analysis and satellite imagery through 0245 UTC. ...TROPICAL WAVES... A tropical wave has an axis from 04N91W to 13N90W, moving westward between 20 and 25 kt. The wave remains evident in tropical wave model diagnostics as well as a maximum in total precipitable water satellite imagery. Scattered moderate convection is evident from 05N to 09N between 90W and 93W. A tropical wave has an axis extending from 03N101W to weak low pres 1010 mb near 08.5N101.5W to 16N101W, moving westward between 15 and 20 kt. The wave is evident in 700 mb tropical wave model guidance streamlines as well as a pronounced maximum in total precipitable water satellite imagery. Numerous moderate and scattered strong convection is observed from 11.5N to 13.5N between 98W and 103W. Scattered moderate and isolated strong convection is seen elsewhere within 120 nm of a line from 11.5N95W to 12.5N101.5W to 07N104.5W. A tropical wave has an axis extending from 04N131W to low pres 1010 mb low near 11.5N131W to 17N130W, moving westward around 20 kt. The wave is associated with broad troughing at 700 mb as depicted in model guidance. The low embedded along this wave remains rather compact in size as observed in satellite-derived wind imagery. Numerous moderate and scattered strong convection is found within 90 nm of 11N131.5W. Scattered moderate isolated strong convection is seen elsewhere from 09N to 13N between 129W and 133W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1008 mb low over NW Colombia near 10N75W to 07N87W to 10N96W to 08N104W to low pres 1009 mb near 12N120W to 12N125W to beyond 11N140W. Aside from convection associated with the tropical waves, numerous moderate and scattered strong convection is taking place within 60 nm of 11.5N121.5W. Scattered moderate and isolated strong convection is present elsewhere from 10N to 13N between 119W and 123W. Scattered moderate and isolated strong convection is occurring from 05N to 10N E of 80W and from 09N to 14N between 111W and 114W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad and weak high pres ridge extends from 32N142W to ESE of the Revillagigedo Islands near 16N108W. 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 all of the waters S of 25N. This extensive swell event is peaking and is bringing seas ranging between 7 and 9 ft to the open waters for all the forecast zones. Seas will begin to slowly subside Tue, then continue to slowly subside for the rest of the week. Gulf of Tehuantepec: Gentle S of SW winds are expected tonight and then gentle to variable winds on Tue. The area of 8 ft seas generated by gap winds during the past couple of days has merged with the much larger area of 8 ft seas that arrived from the S today. Seas in this area will gradually subside Tue through Thu. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: NE to E winds will pulse to fresh speeds during the late night and morning hours for the remainder of this week. Seas from these winds are interacting with the SW swell event resulting in mixed seas in the gulf between 8 and 9 ft. Seas in this area will subside below 8 ft on Wed. Gentle to moderate NE to E 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 guidance suggests that seas are peaking and will gradually subside to around 8 ft Wed, and then to less than 8 ft Thu. REMAINDER OF THE AREA... A weak surface ridge enters the discussion area at 32N142W, then extends to 22N122W and finally to ESE of the Revillagigedo Islands near 16N108W. The gradient between the ridge and lower pressure found along and near the monsoon trough is maintaining moderate to fresh NE to E 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 have decayed and allowed seas N of 28N and W of 133W to subside below 8 ft. Low pressure of 1010 mb is located near 11.5N along the tropical wave that extends from 04N131W to 17N130W. The low will generate fresh to strong winds in the N quadrant over the waters within 150 nm as it tracks westward to west-northwestward to cross 140W by Thu afternoon. 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 25N as confirmed by satellite-derived sea height data. Wave model guidances indicate that the swell will slowly dissipate through Wed allowing for seas to subside to 8 ft or less by Thu afternoon. $$ CAM