809 AXPZ20 KNHC 241603 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...TROPICAL WAVES... A tropical wave has an axis from 04N92W to 13N92W, moving westward near 22 kt. The wave is not as discernible as it has been the past few days in the model diagnostics, but can be seen in model 700 mb streamline analysis. In addition, satellite imagery denotes a more defined inverted-V cloud pattern typical observed with tropical waves that are pronounced at the surface level. The imagery also indicates that a weak and small low pressure center may be forming along the wave near 08N. Scattered moderate convection is seen within 120 nm west from 06N to 08N. A tropical wave has an axis extending from 04N104W to weak low pressure near 09N104W 1010 MB to 16N103.5W, moving westward at 15 kt. Model diagnostic guidance shows this wave as having a rather broad structure. The model 700 mb streamline analysis clearly shows the wave. Satellite imagery shows scattered moderate convection within 180 nm west of the wave and low from 07N-12N. A tropical wave has an axis extending from 04N132W to low pressure near 12N133W 1010 mb to 17N132W. It is moving westward at an estimated motion of 25 kt. The wave is associated with troughing at 700 mb as depicted in model guidance. The low embedded along this wave remains rather compact as was observed in overnight satellite-derived wind imagery. Scattered moderate convection is within 30 nm of 10.5N133W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1010 mb low over NW Colombia near 10N75W to 08N86W to 10N99W to low pressure near 09N104W 1010 MB to 09N111W to low pressure near 11N122W 1009 mb to low pressure near 12N133W 1010 mb and to 08N140W. Aside from convection associated with the tropical waves and associated lows, scattered moderate isolated strong convection is within 240 nm south of the axis between 77W-80W. Scattered moderate convection is within 180 nm south of the axis west of 137W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weak high pressure ridge extends east-southeastward from well northwest of the 250 nm boundary east-southeastward to 25N118W and to near the Revillagigedo Islands. The pressure difference between the ridge and troughing over Baja California and the southwestern United States is maintaining light to moderate northwest winds across the Mexican offshore waters. 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 inducing seas ranging between 7-9 ft over the open waters for all the forecast zones. Seas will begin to slowly subside today, then continue to slowly subside for the rest of the week. Gulf of Tehuantepec: Light and variable winds will become south to southwest winds this afternoon through early Wed, then shift to northwest winds Wed afternoon and become moderate southwest winds Wed night and gentle to moderate west to northwest winds during Thu. 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 generated by the long-period southwest swell of the past several days that propagated into the Gulf of Tehuantepec region yesterday and during the overnight hours. These seas will gradually subside through the end of this week as swell energy dissipates. 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 combined seas of 8 to 10 ft are currently focusing between the Equator and 15N between 90W and 105W. 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 high pressure ridge extends southward from a strong 1030 mb high centered well north of the area at 42N141W through 32N141W, and southeastward from there to 27N135W and weakens as it reaches 25N128W to 22N121w and to near the Revillagigedo Islands. The pressure gradient between the ridge and lower pressure found along and near the monsoon trough is maintaining moderate to fresh NE 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. Low pressure of 1010 mb is located near 12N along the tropical wave that extends from 04N132W to 17N132W. The low will generate fresh to strong winds and seas in the range of 8-10 ft within 150-240 nm of its center in its N quadrant as it tracks WSW to across 140W early on Wed. Another low pressure center of 1010 mb is currently centered near 11N122W. Scattered moderate isolated strong convection is noted within 180 nm of the low in the SW and NW quadrants. Scattered moderate convection is within 60 nm of the low in the SE quadrants. This low will track in a west- southwest motion to near 10.5N128W by Wed morning and to near 11N134W by Thu morning Fresh to strong winds and seas of 8 to 9 ft can be expected in the N quadrant of this low through early Wed before diminishing to mainly fresh thereafter into Thu. Large long-period SW swell continues 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 guidance indicates that swell heights are peaking and that seas in this extensive area will slowly subside through the end of this week. Seas in this area should subside to 8 ft or less by Thu morning. $$ Aguirre