083 AXPZ20 KNHC 301539 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1539 UTC Sun Sep 30 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... Hurricane Rosa centered near 24.4N 118.6W at 30/1500 UTC or 280 nm SW of Punta Eugenia Mexico moving N at 11 kt. Estimated minimum central pressure is 984 mb. Maximum sustained wind speed is 65 kt with gusts to 80 kt. Rosa is expected to weaken to a tropical storm later today, then continue northeast before making landfall over Baja California Norte late Mon. Rosa will then weaken further to depression Mon night into early Tue as it moves across the far northern Gulf of California. 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 centered near 12.1N 105.4W at 30/1500 UTC or 420 nm S of Manzanillo Mexico moving W at 11 kt. Estimated minimum central pressure is 999 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Sergio is expected to continue to intensify and reach hurricane strength by late today as it continues westward and away from the coast of Mexico. Sergio is expected to reach major hurricane strength by early Tue as it starts moving more the northwest. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. ...TROPICAL WAVES... A tropical wave extends along 95W north of 04N into the Gulf of Tehuantepec. Scattered moderate convection is active beyond along 120 nm off the coasts of Guatemala and southern Mexico, likely due more to overnight drainage flow, but possibly being enhanced by the tropical wave. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A segment of the monsoon trough extends from 08N81W to 10N98W. Another segment of the monsoon trough reaches from 16N119W to 10N134W. No significant convection is observed. ...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 over most of the ocean from 10N to 28N between 110W and 130W. A recent altimeter satellite pass showed seas of 8 to 11 ft within 60 nm of the coast of Baja California Sur. The same pass also showed seas to at least 9 ft north of Sergio toward Cabo Corrientes. 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 on Monday, with seas building to around 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, fresh to briefly strong northerly winds will pulse tonight and Mon night in the wake of a tropical wave. Seas will be 5 to 7 ft through most of the day with a component of southerly swell generated from Sergio well to the west of the region. These seas will build to 8 or 9 ft with added pulse of gap winds during the overnight hours. The , with seas building to 9 or 10 ft, mainly during the overnight and early morning hours. 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 mid week, 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 is entering the forecast waters east of 140W and south of 32N currently, weakening the subtropical ridge across the waters north of 20N. A weak cold front will follow behind the trough later today, and eventually sweep across the waters north of 20N through mid week as it weakens further. This will keep trade wind flow minimal farther south into the deep tropics. Long period NW swell will follow the front, eventually mixing with the mixed swell generated from Rosa through mid week. This swell also eventually mix with southeasterly swell generated from Sergio as it moves farther northwest. This pattern will leave the entire region north of 15N in mixed swell greater than 8 ft by mid week, reaching as far east as the entrances to the Gulf of California. $$ Christensen