218 AXPZ20 KNHC 262048 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2048 UTC Wed Sep 26 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 2030 UTC. ...SPECIAL FEATURE... Hurricane Rosa centered near 16.5N 112.2W at 26/2100 UTC or 470 nm WSW of Manzanillo Mexico moving WNW at 9 kt. Estimated minimum central pressure is 987 mb. Maximum sustained wind speed is 70 kt with gusts to 85 kt. Numerous moderate and scattered strong convection is within 120 nm in the NE quadrant and 180 nm in the SE quadrant of Rosa. Scattered moderate to strong convection is within 180 nm in the W semicircle of Rosa. Rosa is forecast to rapidly strengthen through tonight, with slower intensification through the remainder of the week. Swells generated by Rosa will affect portions of the coast of southwestern Mexico and the southern Baja California Peninsula 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northern Colombia near 09N74W to 08N98W, then resumes from 13N116W to 11N125W to 11N136W. Scattered moderate to strong convection is from 03N to 10N to the E of 83W, from 08N to 14.5N between 87W and 97W, from 04N to 07N between 93W and 96W, from 07N to 12N between 100W and 106W, and from 13N to 15N between 120W and 125W. Scattered moderate convection is from 09N to 12N between 114W and 120W and also from 06N to 12N between 123W and 132W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features paragraph above for information on Hurricane Rosa. A ridge extending from 29N120W to 22N113W will continue to retract W of the area ahead of 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 late in the upcoming weekend due to Rosa. In the Gulf of California, light to gentle mostly southerly winds are expected across the gulf waters through Sun night with the flow increasing thereafter due to Rosa. In the Gulf of Tehuantepec, fresh to locally strong northerly flow will pulse the next couple of days, mainly during the overnight and early morning hours. A strong drainage event is expected on Fri night into early Sat as a tropical low passes to the S and the SW of the area. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, moderate to locally fresh E nocturnal drainage flow is expected across and downstream of the Gulf of Papagayo through the upcoming weekend. Gentle to moderate winds are forecast elsewhere N of the monsoon trough which will meander between 09N and 12N. Moderate SW flow is forecast S of the monsoon trough. The pressure gradient will begin to tighten tonight as a surface low develops near 10.5N95.5W. The low and associated conditions will shift W of the area on Thu night. REMAINDER OF THE AREA... See the Special Features paragraph above for information on Hurricane Rosa. A tropical low is just W of the area near 11N142W at 1008 mb. Associated winds to 20 kt and seas to 8 ft in mixed swell are impacting the forecast waters from 12N to 17N to the W of 137W. The low is forecast to continue to move W away from 140W, and associated conditions will diminish and subside E of 140W by late tonight. A broad ridge extends from 29N140W to 29N120W 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. $$ Lewitsky