000 AXPZ20 KNHC 170957 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 822 UTC Mon Jul 17 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 13.4N 130.1W at 0900 UTC or about 1260 nm WSW of the southern tip of Baja California, moving WNW at 10 kt. Estimated minimum central pressure is 960 mb. Maximum sustained winds are 105 kt with gusts to 130 kt. Numerous strong convection is within 90 nm of the center. Elsewhere, scattered moderate to isolated strong convection within 180 nm southeast semicircle and 150 nm northwest semcircle. Fernanda is expected to gradual weaken over the next several days. Large swells will spread and expand out ahead of Fernanda to the NW and W during the next few days, and are expected to reach the Hawaiian Islands early Tuesday. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 for more details. Showers and thunderstorms associated with an area of low pressure near 14N105W, or about 300 nm south of Manzanillo, Mexico, continue to show signs of organization. An earlier scatterometer pass indicated fresh to strong winds within 90 nm in the southeast quadrant of the center. Although upper- level winds are not particularly favorable for development, the low pressure has a high chance of development. Only a small increase in organization of this system could lead to the formation of a tropical depression during the next day or two while it moves west- northwestward at 5 to 10 kt. An area of low pressure centered near 13N116W, or about 740 nm south- southwest of the southern tip of the Baja peninsula has become better defined during the past day or so. Although environmental conditions are only marginally conducive, this system has a medium chance to become a tropical depression during the next day or so before upper- level winds become unfavorable for development as it moves slowly to the west or west-northwest during the next few days. ...TROPICAL WAVES... The axis of a tropical wave extends from the southwest Gulf of Mexico southward across the isthmus of Tehuantepec and into the adjacent Pacific waters to 08N95W, moving west at 10 to 15 kt. Scattered moderate convection is noted from 09N to 12N between 95W and 98W. A tropical wave reaches from 11N105W to low pressure near 14N105W 1008 mb to 10N105W, moving west at 10 to 15 kt. Scattered moderate to isolated strong convection is noted from 10N to 15N between 100W and 105W. See above for more information on the development of the low pressure. A tropical wave reaches from 22N115W to low pressure near 13N115W 1009 mb, moving west at 10 to 15 kt. Scattered moderate to isolated strong convection is noted from 09N to 14N between 115W and 120W. See above for more information on the development of the low pressure. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N85W to 08N95W to low pressure near 14N105W to low pressure near 13N115W to 12N120W, where it breaks to the east of Hurricane Fernanda, then resumes from 11N133W to beyond 10N140W. Other than convection already mentioned near Fernanda and the tropical waves, no signficant convection is observed. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features for information on the area of low pressure SW of Acapulco, Mexico. A surface trough from the coast of southern California southward to off the coast of the Baja California peninsula will continue to 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 remain 5 to 7 ft however, in a mix of northerly and longer period S to SW swell. Farther south, moderate to fresh easterly winds will sweep across the Revillagigedo Islands on the north side of low pressure passing to the WSW of the region by mid week. Gentle southerly flow will persist across the Gulf of California, except for moderate southerly flow over the northern Gulf. Light to gentle variable winds will prevail across the Gulf of Tehuantepec through mid week before fresh northerly gap winds pulse to strong at night. These winds will likely further increase to fresh to strong by the end of the week into next weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, moderate to fresh offshore winds will pulse to fresh each night with nocturnal drainage through the week, occasionally building seas close to 8 ft. Gentle to moderate southerly winds are expected S of the monsoon trough axis. Long period cross-equatorial southerly swell and 6 to 7 ft seas will continue to propagate into the waters reaching the coast of Central America through the day. Another pulse of large southerly swell will move into the waters by Tuesday. REMAINDER OF THE AREA... Please see the special features section for information on Hurricane Fernanda. Strong high pressure is centered N of the Hawaiian Islands along 39N and extends a ridge E to near 39N140W then SE to 25N125W. This is producing moderate to fresh N to NE winds across NW portions of the discussion area. The ridge will build midestly eastward through mid week and tighten the pressure gradient to the N of Fernanda as it moves W of 135W to produce fresh to strong NE winds across much of the NW part of the area, where seas will build to 8-9 ft. Swells generated by Fernanda will propagate away from the center across tropical waters W of 120W the next several days. Northerly swell of 6 to 8 ft will propagate into the waters N of 25N and W of 120W, mixing with southerly swell generated from Fernanda by Tuesday, with 7 to 9 ft combined seas. Elsewhere outside of the region within 360 nm of the path of Fernanda, winds will remain generally light to moderate with 5 to 7 ft seas. $$ Christensen