000 AXPZ20 KNHC 160916 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 916 UTC Sun Jul 16 2017 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Hurricane Fernanda is centered near 12.1N 126.2W at 0900 UTC or about 1130 nm SW of the southern tip of Baja California, moving WNW at 10 kt. Estimated minimum central pressure is 953 mb. Maximum sustained winds are 115 kt with gusts to 140 kt. Numerous strong convection is within 75 nm of the center with scattered moderate isolated strong convection is occurring elsewhere within 180 nm of the center. Fernanda has weakened slightly due to an ongoing eyewall replacement cycle, but is forecast to strengthen again during the next 24 hours or so before gradually weakening thereafter. Large swells will spreading and expanding out ahead of Fernanda to the NW and W during the next few days and are expected to reach the Hawaiian Islands early Tue. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 for more details. An elongated area of 1012 mb low pressure 200 nm S of Acapulco Mexico is associated with a tropical wave moving W at 10 kt across the area. A recent scatterometer pass indicated winds to 20 kt within 60 nm of the center in the northeast quadrant. Scattered moderate convection is observed within 120 nm of the center of the low pressure. The low is forecast to move generally W-NW during the next couple of days and has a medium chance of tropical cyclone formation within the next 48 hours. ...TROPICAL WAVES... A tropical wave extends from 08N101W to the 1012 mb low pressure near 13.5N101W to 17N101W. Please refer to the Special Features section above for more details on the tropical wave and the associated elongated low pressure developing along the wave. A tropical wave is along 114W/115W from 07N to 14N moving W at 15 kt. Although active convection continues from 10N to 15N between 112W and 118W, the tropical wave is becoming less defined as it interacts with the outer circulation of Hurricane Fernanda located to the W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N83W TO 08N92W to 1012 mb low pressure near 13.5N101W to 11N117W, then resumes from 10.5N130W to 07N140W. Aside from the areas of convection already mentioned in the tropical waves section and that associated with Hurricane Fernanda, scattered moderate to isolated strong convection is noted within 60 nm of the coasts of Panama and Costa Rica, and within 120 nm south of the monsoon trough between 90W and 95W. Scattered moderate convection is also observed within 90 nm south of the monsoon trough axis between 135W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features for information on a broad area of low pressure south of Acapulco. A surface trough will develop through Monday from the coast of southern California southward to off the coast of the Baja California peninsula. This will block the advance of the subtropical ridge into the region and maintain generally gentle to moderate winds off the Baja California peninsula through late week. Seas will still be 5 to 7 ft however in a mix of northerly and longer period south to southwest swell. Farther south, moderate to fresh easterly winds will sweep across the Revillagigedo Islands on the north side of low pressure passing to the west of the region early to mid week. Gentle southerly flow will persist across the Gulf of California, except for moderate southerly flow over the northern Gulf. Fresh gap winds will pulse across the Gulf of Tehuantepec starting mid week related to high pressure north of the area and lower pressure to the south related to passing tropical waves. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, moderate offshore winds will pulse to fresh each night with nocturnal drainage through Monday morning, increasing fresh to strong thereafter. Gentle to moderate southerly winds are expected south of the monsoon trough axis. Long period cross-equatorial southerly swell and 6 to 7 ft seas will continue to propagate into the waters W of Colombia and Ecuador, with a reinforcing pulse of swell moving into the area this morning, reaching the Central America coast Saturday night and Sunday. Another pulse of large southerly swell will move into the waters by Tue. REMAINDER OF THE AREA... Please see the special features section for information on Hurricane Fernanda. The post-tropical remnant low of Eugene has finally dissipated, leaving a weak trough from 28N131W to 25N127W. Swell generated by Fernanda will propagate away from the center across tropical waters west of 120W the next several days. It is expected to cross 140W and move into the Central Pacific by through mid week. Northerly swell of 6 to 8 ft will propagate into the waters north of 25N and west of 120W starting Monday, mixing with southerly swell generated from Fernanda by Tuesday with 7 to 9 ft combined seas. Elsewhere outside of the region within 300 nm of the path of Fernanda, winds will remain generally light to moderate with 5 to 7 ft seas. $$ Christensen