000 AXPZ20 KNHC 270945 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Sep 27 2016 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 0945 UTC. ...SPECIAL FEATURES... Tropical Storm Roslyn centered at 17.8N 117.7W at 27/0900Z, or about 615 sm wsw of the southern tip of the Baja California Peninsula, moving ne, or 050 degrees at 6 kt. The estimated minimum central pressure is 1003 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Currently, scattered moderate isolated strong convection is observed within 240 nm over the ne quadrant of the center. Roslyn is forecast to weaken to a tropical depression tonight, and further weaken to a remnant low late Wed, and gradually dissipate on Thu. Refer to the latest NHC forecast/advisory under AWIPS/WMO headers WTPZ23 KNHC/TCMEP3, or visit the NHC website at http://hurricanes.gov for additional details. Tropical Storm Ulika is centered just w of the area at 12.1N 140.4W at 27/0900Z, or about 1105 sm ese of Hilo hawaii, moving n, or 350 degrees at 3 kt. The estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Numerous strong convection is currently flaring within 30 nm of the center, surrounded by scattered moderate isolated strong convection elsewhere within 180 nm e and 60 nm w semicircles of the center. Ulika is forecast to move ne and back into the discussion area today. When the center is w of 140W, refer to the latest CPHC forecast/advisory under AWIPS/WMO headers WTPA22 PHFO/TCMCP2, or visit the CPHC website at http:www.prh.noaa.gov/cphc/ for additional details. After the center moves e of 140W, refer to the latest NHC forecast/advisory under AWIPS/WMO headers WTPZ24KNHC/TCMEP4,or visit the NHC website at http://hurricanes.gov for additional details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends w off the Pacific coast of Costa Rica at 09N78W to 10N86W, then dips sw to 12N97W to 09N112W where it loses identity. Scatterometer winds indicate that the monsoon trough resumes just sw of T.S. Roslyn at 13N120W to 12N138W. Isolated moderate to strong convection is observed within 150 nm either side of a line 05N77W to 07N85W to 12N101W to 08N114W. 120 nm either side of a line from 12N126W to 13N136W. Scattered moderate isolated strong convection is observed within 75 nm either side of a line from 11N87W to 13N90W, within 75 nm either side of a line from 14N94W to 12N98W, and within 30 nm either side of a line from 15N98W to 17N103W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sub-tropical ridge axis extends from nw to se across the offshore zones w of the Baja Peninsula terminating near 24N112W. Light to gentle n-ne winds are observed w of the Baja Peninsula with little change expected through Wed. Scattered convection, strong e winds and combined seas of 7 to 11 ft will expand ne across the waters generally from 18N to 23N w of 114.5W through Wed as tropical cyclone Roslyn continues northward. The subtropical ridge will extend from 29N120W to 20N106W on Fri with gentle n flow returning. The pressure gradient will tighten this weekend with moderate to fresh nw winds, and 5 to 8 ft seas, w of Baja on Sun. Light to gentle nw winds are expected across the entire Gulf of California late today with little change expected through Thu. Light and variable winds expected on Fri across the far northern gulf waters. Strong drainage flow expected across the Gulf of Tehuantepec beginning Wed night, and then pulsing through the upcoming weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle southerly winds expected n of the monsoon trough, while gentle to locally moderate s to sw flow is expected s of the monsoon trough through the upcoming weekend. Combined seas of 3 to 6 ft primarily in long-period sw swell is expected this week. REMAINDER OF THE AREA... A cold front moving southeast out of the north central Pacific will weaken the subtropical ridge to the north of the region for the next couple of days. This will maintain gentle to moderate northeast winds across most of the region outside of areas of tropical cyclone activity and north of the monsoon trough with 5 to 6 ft seas. Moderate to occasionally fresh southerly flow will dominate south of the monsoon trough with 6 to 7 ft seas. $$ Nelson