723 AXPZ20 KNHC 271535 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1535 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Hurricane Rosa centered near 17.2N 115.4W at 27/1500 UTC or 460 nm SW of the southern tip of Baja California moving W at 10 kt. Estimated minimum central pressure is 970 mb. Maximum sustained wind speed is 90 kt with gusts to 110 kt. Associated numerous moderate to strong convection is within 150 nm of the center, except within 120 nm in the NW quadrant of Rosa. Additional scattered moderate and isolated strong convection is in a band between 180 nm and 360 nm in the SE semicircle. 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. A broad area of low pressure is near 10N93W, or a few hundred nautical miles S of the southern coast of Mexico, moving WNW around 5 kt. Associated scattered moderate and isolated strong convection is within 270 nm in the SE semicircle and within 360 nm in the NW semicircle. Fresh to strong winds are already within 150 nm in the N semicircle of the low along with seas of 8 to 9 ft. 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 near 10N75W to low pressure near 10N93W to 08N100W, then resumes from 11N116W to 09N134W. The intertropical convergence zone axis extends from 09N134W to 12N140W. Scattered moderate and isolated strong convection is from 03N to 07N between 77W and 85W, and also from 07N to 12N between 102W 107W. Scattered moderate convection is from 11N to 13N between 124W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features paragraph above for information on Hurricane Rosa and the tropical low near 10N93W. A ridge along 26N 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 conditions to the N of 27N thereafter with tropical storm conditions possible N of 29N on 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 10N93W. 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 26N/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