368 AXPZ20 KNHC 260916 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0915 UTC. ...SPECIAL FEATURE... Tropical Storm Rosa is centered near 15.1N 109.7W at 26/0300 UTC or 390 nm SW of Manzanillo Mexico moving WNW at 8 kt. Estimated minimum central pressure is 997 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Currently numerous moderate to strong convection is observed in bands within 90 nm southeast and 270 nm northwest semicircles of center. Rosa is forecast to soon intensify to hurricane strength with continued gradual strengthening thereafter for the next few days. Associated winds and seas are forecast to spread across the offshore waters of Mexico W of 105W during the next few days, and recurve northeast across the offshore waters west of Baja California early next week. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP5/WTPZ35 KNHC for more details. ...TROPICAL WAVES... A tropical wave formally along 104W has lost identity. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends W off the Pacific coast of Colombia at 08N78W to 09N94W then turns northwest to 12N100W where it loses identity. The monsoon trough resumes west of Rosa at 13N115W and continues southwest to near an embedded surface low at 10.5N140W. Scattered moderate isolated strong convection is observed across the Gulf of Panama...within 150 nm of a line from 10.5N86W to 13N94W, within 90 nm of a line from 06.5N87W to 06.5N91W, within 75 nm of a line from 14.5N97.5W to 20N107W, within 30 nm of a line from 15.5N118W to 13.5N125W and within 120 nm of a line from 10N117W to 09N130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features paragraph above for information on Tropical cyclone Rosa. A west to east ridge along 21N will gradually retract west of the area ahead of Tropical Cyclone Rosa. Gentle to moderate northwest flow is forecast west of the Baja California through Fri, then becoming northerly early this upcoming weekend, with marine conditions deteroiating late in the upcoming weekend. Gulf of California: Light to gentle mostly southerly winds expected across the gulf waters through Sun night with the flow ind=creasing thereafter. Gulf of Tehuantepec: Fresh to locally strong northerly flow forecast through late Thu morning. A strong drainage event is expected on Fri night into early Sat as a tropical low passes to the southwest. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Moderate to locally fresh east nocturnal drainage flow expected across and downstream of the Gulf of Papagayo through the upcoming weekend. Gentle east winds are forecast through this morning elsewhere north of the monsoon trough which is meandering between 09N and 12N. Moderate southwest flow is forecast south of the monsoon trough. The pressure gradient will begin to tighten tonight as a surface low develops near 10N94W. The low and associated conditions will shift west of the area on Thu night. REMAINDER OF THE AREA... See the Special Features paragraph above for information on Tropical Cyclone Rosa. A broad ridge continues across the subtropics accompanied by moderate to locally fresh anticyclonic flow south of 23N west of 120W. A series of weak cold fronts, or troughs, will sweep east across the far NW waters through the upcoming weekend accompanied by a moderate west to northwest wind shift. $$ Nelson