596 AXPZ20 KNHC 261552 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1552 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURE... Hurricane Rosa centered near 16.1N 111.4W at 26/1500 UTC or 440 nm WSW of Manzanillo Mexico moving WNW at 9 kt. Estimated minimum central pressure is 990 mb. Maximum sustained wind speed is 65 kt with gusts to 80 kt. Numerous moderate and scattered strong convection is within 120 nm in the E semicircle of Rosa. Scattered moderate to strong convection is within 210 nm in the SW quadrant and 270 nm in the NW quadrant of Rosa. Rosa is forecast to rapidly strengthen through tonight, with slower intensification for the next couple days thereafter. 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 low pressure over northern Colombia near 09.5N75W to 08N80W to 09N90W to 13N103W, then resumes from 13N115W to 12N125W to 11.5N135W. Scattered moderate and isolated strong convection is from 05N to 09N between 77W and 84W, within an area bounded by 15N92W to 08N86W to 03N90W to 05N97W to 10N99W to 15N92W, within an area bounded by 19N106W to 13N100W to 07N100W to 10N104W to 19N106W, from 09.5N to 13N between 112W and 120W, from 14N to 16N between 120W and 124W, and also from 07N to 12N between 125W and 131W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features paragraph above for information on Hurricane Rosa. A ridge extending from 28N120W 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 E winds are forecast through this morning elsewhere N of the monsoon trough which is meandering 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 10N141W at 1008 mb. Associated winds to 20 kt and seas to 8 ft in mixed swell are impacting the forecast waters within 240 nm in the N and E quadrants. 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 32N140W to 28N120W 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