000 AXPZ20 KNHC 280930 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Wed Sep 28 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 0930 UTC. ...SPECIAL FEATURES... Hurricane Ulika is centered at 13.9N 139.0W, or about 1135 sm ese of Hilo Hawaii at 09 UTC Sep 28, moving nne, or 030 degrees at 6 kt. The estimated minimum central pressure is 992 mb. The maximum sustained wind speed is 65 kt with gusts to 80 kt. Currently, scattered strong convection is observed within 60 nm of the center, with a area of scattered moderate convection noted elsewhere within 180 nm over the se quadrant of the center. Ulika is forecast to remain a hurricane for 24 hours, then weaken to a tropical storm with the center moving w of 140W late in a couple of days. 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. After the center moves 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. Tropical Storm Roslyn is centered at 20.2N 115.5W, or about 405 sm wsw of the southern tip of the Baja California Peninsula at 09 UTC Sep 28, moving nne, or 025 degrees at 8 kt. The estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 35 kt with gusts to 40 kt. Currently, scattered moderate convection is observed well ne of the center, within 90 nm either side of a line from 22N114W to 24N114W. Roslyn is forecast to weaken to a tropical depression today, and further weaken to a remnant low tonight, and gradually dissipate in about 3 days. 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends wnw off the Pacific coast of Costa Rica at 09N84W to 11N105W to 05N118W where it loses identity. Scatterometer winds indicate that the monsoon trough resumes just sw of tropical cyclone Roslyn near 13N117W to 13N136W. Isolated moderate and strong convection is noted within 150 nm either side of a line from 04N77W to 09N102W to 07N118W, and within 75 nm either side of a line from 12N126W to 15N132W. Scattered moderate isolated strong convection is observed n of 11N between 93W and 98W to include the Gulf of Tehuantepec. ...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 24N110W. Light to gentle n-ne winds are observed w of the Baja Peninsula. Fresh to strong e to se winds,and combined seas of 7 to 11 ft will expand n across the far offshore waters, generally from 11N to 24N w of 115W today and tonight, as tropical cyclone Roslyn continues north-northeastward, and later nw. The subtropical ridge will rebuild from 29N120W to 22N106W on Fri with gentle n flow returning, except becoming moderate along the Baja coast during the overnight hours. The pressure gradient will tighten this weekend, with moderate to fresh nw winds, and 5 to 8 ft seas, w of Baja on Sun, and fresh to strong nw winds developing Sun night. 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 across the far northern gulf waters beginning on Thu night. Fresh drainage flow expected across the Gulf of Tehuantepec tonight, increasing to fresh to strong flow on Thu, 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 are 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... As tropical cyclone Ulika moves w of 140W and tropical cyclone Roslyn dissipates, the pressure gradient will tighten around the subtropical ridge, with fresh anticyclonic winds expected between the monsoon trough/ITCZ and the ridge on Mon, with combined seas of 6 to 7 ft. The gradient will then relax some by the middle of next week. $$ Nelson