256 AXPZ20 KNHC 290340 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 209 UTC Sat Sep 29 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 0300 UTC. ...SPECIAL FEATURES... Hurricane Rosa centered near 18.4N 118.0W at 29/0300 UTC or 540 nm SW of the southern tip of Baja California moving NNW at 8 kt. On the forecast track the center of Rosa will be approaching Baja California on Monday. Estimated minimum central pressure is 964 mb. Maximum sustained wind speed has decreased to 95 kt with gusts to 115 kt. Scattered moderate to strong convection is observed within 150 nm of the center of Rosa. This tropical cyclone is expected to bring heavy rain to Baja California and the SW of United States. Swells generated by Rosa will affect portions of the coasts of southwestern Mexico, the southern Baja California Peninsula, and southern California late this week and over the weekend. These swells are likely to cause life- threatening surf and rip current conditions. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP5/WTPZ35 KNHC for more details. Satellite and NOAA Hurricane Hunter data indicate that an area of low pressure centered a few hundred miles south of Acapulco, Mexico, is producing tropical-storm-force winds. However, the data also show that the system does not have a well-defined center. Environmental conditions are very conducive for further development, and the low is expected to become a tropical storm on Saturday while it moves west-northwestward well offshore of the coast of Mexico. Based on scatterometer data a gale warning is in effect in association with this system. Seas will build accordingly, possibly reaching 15 ft by Sunday within 120 nm to the north of the low pressure. The low pressure is currently near 12N99W. A cluster of moderate to strong convection is noted within 180 nm NE quadrant of center. Scattered moderate and isolated strong convection is observed elsewhere from 08N-13N between 95W-105W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N77W to 10N90W to the low pressure near 12N99W, then resumes SW of Hurricane Rosa from 13N122W to 07N140W. Scattered moderate near 06N87W, and from 08N-13N between 120W-130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features above for information on Hurricane Rosa and the tropical low near 12N99W. A ridge along 27N will retreat ahead of Hurricane Rosa. Gentle to moderate NW flow west of the Baja peninsula will become northerly on Sat, with marine conditions deteriorating across southern waters by Sat night as Rosa approaches the area, with hurricane or tropical storm conditions spreading NE into the waters W of Baja California Norte through early next week. In the Gulf of California, light to gentle southerly winds are expected through Sun night. The southerly flow will increase to near gale force N of 27N thereafter, with tropical storm conditions possible N of 29N Mon night and Tue from Rosa. In the Gulf of Tehuantepec, fresh nocturnal offshore northerly flow will pulse through Sat, becoming strong by Sun night with seas reaching 9 ft by early Mon. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Numerous showers and scattered thunderstorms are likely in the the waters off Guatemala and El Salvador through early Sat. The monsoon trough will meander between 09N and 12N through Tue, with gentle to moderate winds expected on either side of the trough axis. Moderate to fresh E nocturnal drainage flow is expected in the Gulf of Papagayo through Sun night. REMAINDER OF THE AREA... See Special Features above for information on Hurricane Rosa. A broad ridge extends along 27N with gentle anticyclonic flow N of the ridge, and moderate to fresh trades S of 23N. A weak cold front will sweep across the waters north of 27N through early next week, accompanied by a W to NW wind shift. NW swell may propagate into the N central waters early next week. $$ GR