144 AXPZ20 KNHC 260619 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURE... Tropical Storm Rosa centered near 15.1N 109.7W at 26/0300 UTC or 390 nm SW of Manzanillo Mexico moving W-NW 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 120 nm southeast and 240 nm northwest semicircles of center. Rosa is forecast to intensify to hurricane strength late tonight with continued strengthening thereafter for the next few days. Associated winds and seas are forecast to spread into the offshore waters of Mexico W of 105W during the next few days, continuing to shift later recurving northeast across the offshore of west of Baja California early next week. Large swells associated with Rosa are likely to impact these areas as well as the entrance to the Gulf of California by the end of the week. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP5/WTPZ35 KNHC for more details. ...TROPICAL WAVES... A tropical wave is analyzed from 05N104W to 17N103W with isolated moderate and strong convection flaring north of 10N within 210 nm east of the wave axis. Expect this wave to lose identity within 24 hours. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends W off the Pacific coast of Colombia at 08N78W to 10N95W then turns northwest to 12N101W where it loses identity. The monsoon trough resumes where it loses identity west of Rosa at 12.5N115W and continues southwest to an embedded surface low at 10N138W. Scattered moderate isolated strong convection is observed within 60 nm of the coast from 86W to 90W and from 98W to 106W. Isolated moderate and strong convection is noted within the area bounded by 17N104W to 05N81W to 07N105W to 17N104W and within 240 nm either side of a line from 14N117W to 09N129W to 11N140W. ...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 northwest ahead of Rosa. Gentle to moderate northwest flow is forecast west of the Baja California through Fri becoming northerly during the weekend with 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 strong northerly flow forecast through Fri except briefly relaxing during the mid afternoons. A strong drainage event expected on Fri night into early Sat as a tropical low passes to the south. 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 through the upcoming weekend. Gentle east winds are forecast through Wed 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 on Wed night as a surface low develops near 10N94W and moves west of the ares by early Fri. 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. $$ Nelson