000 AXPZ20 KNHC 100254 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 254 UTC Wed Oct 10 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... 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 within 180 nm in the north semicircle, and 150 nm in the south semicircle. Large swells associated with Sergio will continue to mix with long period NW swell, and increasingly a component of SW swell, creating confused seas across a large portion of the discussion waters. The swell will continue 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 south 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 10N to 12N between 95W and 100W. 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 Oaxaca near 16N97W to 11N105W to 10N115W. Another segment of the monsoon trough to the west of Sergio extends from 12N130W to 10N135W to beyond 10N140W. Scattered moderate convection is evident within from 11N to 15N between 90W and 100W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for details on T.S. Sergio. Recent altimeter satellite passes indicated 7 to 9 ft seas over the Pacific offshore areas of Baja California. This in a mix of southerly swell from Sergio, and longer period and decaying NW swell. These swell could create hazardous surf, as well as dangerous marine conditions near marinas and jetties, for Baja California and the Mexican coast between Manzanillo and Mazatlan. 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 following 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 west 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 west. 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. The swell will gradually decay and seas subside in this area into Sat. $$ Christensen