053 AXPZ20 KNHC 272112 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2112 UTC Thu Sep 27 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... Hurricane Rosa centered near 16.9N 115.9W at 27/2100 UTC or 500 nm SW of the southern tip of Baja California moving W at 9 kt. Estimated minimum central pressure is 953 mb. Maximum sustained wind speed is 110 kt with gusts to 135 kt. Associated numerous moderate to strong convection is within 180 nm of the center of Rosa, except 150 nm in the NW quadrant. Scattered moderate and isolated strong convection is elsewhere between 180 nm and 360 nm in the SE semicircle of Rosa. Swells generated by Rosa will affect portions of the coasts of southwestern Mexico, the southern Baja California Peninsula, and southern California late this week and over the weekend. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP5/WTPZ35 KNHC for more details. An 1008 mb area of low pressure near 11N97W, or a few hundred miles S of the Gulf of Tehuantepec has become better organized since yesterday while moving WNW around 5 kt. Associated scattered moderate and isolated strong convection is from 10N to 15N between 90W and 101W. Additional widely scattered moderate and isolated strong convection is within 300 nm in the SE quadrant. Fresh to strong winds and seas of 8 to 10 ft are within 180 nm in the N semicircle of the low. This low will likely track WNW through the next several days right along the outer boundary of the offshore waters zones. The low has a medium potential for tropical cyclone development in the next 48 hours. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from northern Colombia near 10N74W to low pressure near 11N97W to 10N105W, then resumes from 13N118W to 09N133W. The intertropical convergence zone axis extends from 09N133W to 10N140W. Scattered moderate and isolated strong convection is from 04N to 08N between 79W and 87W, from 04N to 10N between 101W and 105W, and also from 10N to 12N between 128W and 131W. Also, scattered moderate and isolated strong convection is within 180 nm W of a line from 07N101W to 15N106W to 23N104W. Upper level diffluence is over this area with an upper level anticyclone near 17N106W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features paragraph above for information on Hurricane Rosa and the tropical low near 11N97W. A ridge along 27N will continue to retract W of the area ahead of Hurricane Rosa. Gentle to moderate NW flow is forecast W of the Baja California through Fri, then becoming northerly early this upcoming weekend, with marine conditions deteriorating across the southern waters as early as Sat night, with these conditions spreading NE the waters W of Baja California Norte through early next week. In the Gulf of California, light to gentle mostly southerly winds expected across the gulf waters through Sun night. The southerly flow will increase to near gale force to the N of 27N thereafter with tropical storm conditions possible N of 29N on Mon night and Tue due to Hurricane Rosa. In the Gulf of Tehuantepec, nocturnal offshore northerly flow will pulse to fresh to strong through the next several days with seas briefly building to 8 to 9 ft during the strongest winds. The tropical low discussed above is forecast to move by S of the area through the end of the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... See the Special Features paragraph above for information on the tropical low near 11N97W. In the Gulf of Papagayo, moderate to locally fresh E nocturnal drainage flow is expected through Sun night, with seas occasionally building up to 7 ft. Elsewhere, mainly gentle and variable winds are forecast N of the monsoon trough which is meandering between 09N and 12N, with moderate SW flow S of the monsoon trough through the next several days. Seas will be mainly 4 to 6 ft, except 1 to 3 ft in the Lee of the Galapagos Islands. REMAINDER OF THE AREA... See the Special Features paragraph above for information on Hurricane Rosa. A broad ridge extends along 27N with gentle to moderate anticyclonic flow N of 23N, and moderate to fresh flow S of 23N. A series of weak cold fronts, or troughs, will sweep E across the far NW waters through the upcoming weekend accompanied by a moderate W to NW wind shift. Seas will be mainly 4 to 7 ft in mixed swell through the forecast period. A set of NW swell may propagate into the NW and N central waters early next week. $$ Lewitsky