323 AXPZ20 KNHC 012144 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2143 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Tropical Storm Rosa centered near 28.1N 116.2W at 01/2100 UTC or 60 nm WNW of Punta Eugenia Mexico moving NNE at 9 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Rosa is completely exposed, with no significant showers or thunderstorms in its vicinity. Rosa will move across the southern half of Baja California Norte this evening and tonight, then weaken to a depression over the northern Gulf of California late tonight into 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 the southwest 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 northwest of Clipperton Island near 11.3N 111.0W at 01/2100 UTC or 600 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. Numerous moderate to strong convection is noted within 150 nm of the center of Sergio. In addition, scattered moderate to isolated strong convection is active within 60 nm either side of a band reaching from 06N113W to 09N108W. Strengthening is forecast during the next 48 hours, and Sergio is expected to become a hurricane tonight as it continues westward and a major hurricane by late Thu as it starts moving more to the northwest. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP1/WTPZ31 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N76W to 11N100W. Another segment of the monsoon trough reaches from 15N120W to beyond 10N140W. Scattered moderate convection is noted within 30 nm of the monsoon trough between 85W and 100W. Scattered moderate convection is also noted within 60 nm of the monsoon trough between 120W and 125W. ...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, a recent scatterometer pass confirmed fresh to strong west winds across the far northern Gulf, ahead of Rosa. These winds will veer more SE to S tonight as Rosa approaches, 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 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 30N130W to 24N140W 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