000 AXPZ20 KNHC 092147 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1912 UTC Tue Oct 9 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 2115 UTC. ...SPECIAL FEATURES... Newly downgraded Tropical Storm Sergio centered near 16.9N 126.5W at 09/2100 UTC or 1000 nm WSW of the southern tip of Baja California moving ENE at 8 kt. Estimated minimum central pressure is 990 mb. Maximum sustained wind speed has decreased to 60 kt with gusts to 75 kt. Numerous moderate and isolated strong convection is noted in the NE quadrant within 270 nm of the center. Scattered moderate convection is found elsewhere from 09N to 20N between 122W and 129W. Large swells associated with Sergio will continue to mix with long period NW swell creating confused seas across a large portion of the discussion waters, with the swell also continuing to impact the coast of Mexico the next several days as Sergio makes its way to central Baja California Sur by Fri. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP1/WTPZ31 KNHC for more details. Recent satellite-derived sea height data showed moderate to fresh SW flow along the S side of the monsoon trough pushing into northern Central America and southern Mexico. These winds are expected to pulse to strong speeds this evening from 11N to 12.5N between 94W and 97W. This setup could produce heavy rainfall across Honduras, El Salvador, Guatemala, and southern Mexico. These rains may cause flash floods and mudslides in areas of mountainous terrain. The heavy rainfall threat is expected to shift northward during the next day or so as the trough weakens. Refer to your local meteorological service for specific information on this potentially dangerous weather pattern. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough reaches from along the coast of the Mexican state of Chiapas near 15N94W to 10N111W to 11N115W. Another segment of the monsoon trough to the W of Sergio extends from 12N130W to 09N135W to beyond 07N140W. Scattered moderate and isolated strong convection is evident within an area bounded by a line from 14N87W to 06N108W to 18N100W to 14N87W and from 07N to 09N between 134W and 138W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for details on Hurricane Sergio. Mainly moderate to fresh NW to N winds and mixed swells from Sergio as well as long period NW swell will support combined seas of 7 to 11 ft west of 110W for the next couple of days. Light to gentle onshore winds and seas of 5 to 8 ft in mixed southerly and westerly swell will prevail east of 110W. Conditions are forecast to rapidly deteriorate across the Baja California waters as Sergio moves closer on Thu. Conditions will then worsen for the central and northern Gulf of California Thu night and Fri. Winds and seas rapidly diminish Fri night and Sat as Sergio dissipates far inland. Farther south, the persistent SW flow has been supporting scattered moderate showers and thunderstorms extending around 400 nm W-SW of the Guatemala and Chiapas coasts. The SW flow is flowing across the Isthmus of Tehuantepec into the northwest Caribbean and Gulf of Mexico where Hurricane Michael is active. As Michael moves northward, the SW flow over the eastern Pacific will diminish slightly and shift northward and focus over southern Mexico, then persist through the remainder of the week. Wave guidance suggests seas may be as high as 10 ft in the plume of persistent SW flow. These seas will subside gradually over the next couple of days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please refer to the Special Features section for additional details regarding the heavy rainfall potential for Central America. Fresh SW monsoonal flow and 8 ft seas will persist off Guatemala through Wed night then conditions will diminish. Moderate SW flow will then continue through the week. Long period SW swell will continue to propagate from the Southern Hemisphere into the waters off southern Central America, with combined seas building to 8 or 9 ft off Panama and Costa Rica by Thu. REMAINDER OF THE AREA... Please see the Special Features section for details on Hurricane Sergio. Outside of the influence of Sergio, moderate to fresh trades will prevail. The pressure gradient will lessen across the waters north of 20N and W of 120W through the end of the week as high pressure centered NW of the discussion area weakens in response to low pres approaching from the W. Meanwhile, confused seas are likely to continue due to long period NW swell along with mixed shorter period swell generated from Sergio. Conditions are likely to improve by the end of the week after Sergio makes landfall. Long period SW swell arriving from the Southern Hemisphere will also contribute to combined seas and maintain sea heights between 8 and 9 ft along the equator between 100W and 130W through Fri, then seas in this area will subside. $$ CAM