850 AXPZ20 KNHC 011542 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1542 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Tropical Storm Rosa centered near 27.5N 116.5W at 01/1500 UTC or 80 nm WSW of Punta Eugenia Mexico moving NNE at 10 kt. Estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Scattered moderate convection is observed north of 29N between 115W and 118W. Rosa will move across the southern half of Baja California Norte late today and tonight, then weaken to a depression over the northern Gulf of California early Tue morning. Rosa's remnants are then expected to move across the Desert Southwest on Tuesday. Currently, heavy rain associated with Rosa continue to spread northward across northern Baja california into the extreme SW of United States. Swells generated by Rosa are affecting portions of the coasts of southwestern Mexico, most of the west coast of the Baja California peninsula, and southern California, and will persist 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 centered near 11.5N 109.5W at 01/1500 UTC or 540 nm SW of Manzanillo Mexico moving W at 12 kt. Estimated minimum central pressure is 995 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Strengthening is forecast during the next 48 hours, and Sergio is expected to become a hurricane later today, and a major hurricane by Wednesday morning. Currently, numerous moderate to strong convection is noted within 120 nm of the center of Rosa. Numerous moderate to isolated strong convection is also ongoing seen in bands within 270 nm in the NW and SE semicircles of the center. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. ...TROPICAL WAVES... A tropical wave extends along 100W north of 04N into the State of Guerrero, Mexico. Scattered moderate isolated strong convection, associated in part with the tropical wave but also due to overnight drainage convergence off the coast is noted in within 60 nm of a line from 13N96W to 14N102W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N78W to 11N100W. Another segment of the monsoon trough reaches from 16N120W to beyond 10N140W. Scattered moderate convection is noted from 06N to 10N between 80W and 90W, and from 06N to 09N between 94W and 99W. Similar convection is noted from 10N to 13N between 125W and 131W. A cluster of moderate to isolated strong convection is N of 14N between 92W and 95W. This convective activity is affecting the eastern part of the Gulf of Tehunatepec. ...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 20N to 30N east of 120W. Farther south, swell generated by Sergio in excess of 8 ft is observed in various altimeter passes reaching to just beyond 120 nm off the coast of Mexico between Acapulco and Cabo Corrientes. Some of this swell may be reaching the coastal areas and producing dangerous surf. In the Gulf of California, the southerly flow will increase to near gale force N of 27N today, with seas building to around 10 ft late today north of Tiburon Island. Tropical storm conditions from Rosa are possible across the northern Gulf of California today and tonight. Winds and seas will diminish rapidly thereafter over the northern Gulf of California through late Tue. In the Gulf of Tehuantepec, pulsing winds of 20 to 30 kt are expected during the overnight and early morning hours through at least early Wed morning. Seas are forecast to build to 9 or 10 ft with the strongest winds. 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. Scattered showers and thunderstorms are possible near the coast, mainly at night. REMAINDER OF THE AREA... See Special Features above for information on Tropical Storm Rosa and Tropical Storm Sergio. A cold front reaching from 30N132W to 25N140W will sweep eastward across the waters north of 20N through mid week, but become diffuse before reaching 120W. 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 long period 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. $$ Christensen