478 AXPZ20 KNHC 010327 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 232 UTC Mon Oct 1 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... Rosa was downgraded to tropical storm status at 01/000 UTC. Additional weakening is forecast during the next couple of days while Rosa approaches and moves over the northern Baja California peninsula. Rosa is expected to dissipate over northwestern Mexico or the southwestern United States by Tuesday. At 01/0300 UTC, Rosa is centered near 26.0N 117.6W or 175 nm SW of Punta Eugenia Mexico moving NNE at 10 kt. Estimated minimum central pressure is 989 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Numerous moderate to strong convection is noted within 120 nm NE quadrant. On the forecast track, the center of Rosa will approach the central and northern Baja California peninsula on Monday. Rosa's remnants will then move across the Desert Southwest on Tuesday. Flooding rains from Rosa are expected across northwest Mexico and the southwest United States over the next few days. Swells generated by Rosa will affect portions of the coasts of southwestern Mexico, most of the west coast of the Baja California peninsula, and southern California through Tuesday. These swells are likely to cause life- threatening surf and rip current conditions. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 KNHC for more details. Farther south, Tropical Storm Sergio is centered near 11.6N 107.3W at 01/0300 UTC or 475 nm SSW of Manzanillo Mexico moving W at 10 kt, and this general motion is expected through Monday night. A turn toward the west-northwest is expected on Tuesday. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Sergio is expected to continue to intensify and reach hurricane strength by late tonight or on Mon, and a major hurricane by Tuesday night. Currently, numerous moderate to strong convection is noted within 105 nm NE semicircle. Scattered moderate convection is elsewhere from 08N to 13N between 104W and 112W. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. ...TROPICAL WAVES... A tropical wave extends along 98W north of 04N into southern Mexico west of the Gulf of Tehuantepec. No significant convection is noted. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from a 1006 mb low pressure over Colombia near 06N76W to 08N81W to 09N90W to 09N100W. Another segment of the monsoon trough reaches from 14N123W to 10N140W. Scattered moderate isolated strong convection is noted from 06N to 11N between 80W and 90W. Scattered moderate is from 10N to 15N between 122W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features above for information on Hurricane Rosa and Tropical Storm Sergio. Swell associated with Rosa will continue to propagate across the offshore forecast waters W of Baja California. Seas in the form of mixed swell in excess of 8 ft are observed from 13N to 30N between 110W and 126W. In the Gulf of California, gentle to moderate southerly winds are expected through tonight. The southerly flow will increase to near gale force N of 27N Mon, with seas building to around 10 or 11 ft late Mon north of Tiburon Island. Tropical storm conditions from Rosa are possible across the northern Gulf of California Mon and Mon night. Winds and seas will diminish rapidly thereafter over the northern Gulf of California through late Tue. In the Gulf of Tehuantepec, an earlier scatterometer pass captured fresh to strong gap winds. These pulses will persist tonight into Mon morning, and Mon night into Tue morning. These marine conditions are expected to persist through mid week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough will meander between 09N and 12N through Fri, 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 tonight. REMAINDER OF THE AREA... See Special Features above for information on Hurricane Rosa and Tropical Storm Sergio. A pre-frontal trough has entered the forecast waters and extends 30N131W to 25N140W. A cold front follows the trough and stretches from 31N136W to 27N140W. A weak ridge is seen between Rosa and the trough covering mainly the waters N of 20N W of 125W. This weather pattern will keep the trade wind flow minimal farther south into the deep tropics. NW swell in the wake of the front will propagate across the NW waters through Tue, while seas associated with Rosa will subside to less than 8 ft W of the Baja California Peninsula. Later in the week, seas associated with Sergio will mix with additional pulses of NW swell. By Thu, seas of 8 ft or greater are expected to cover most of the waters N of 10N W of 105W, including the entrance of the Gulf of California. $$ GR