000 AXPZ20 KNHC 281617 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Tropical Storm Ulika is centered near 14.5N 138.7W 995 mb at 1500 UTC moving NNE or 030 DEG at 6 kt. The maximum sustained wind speed has diminished to 60 kt with gusts to 75 kt. convection has gradually decreased in the past several hours, with scattered moderate to strong occurring within 60 nm of thecenter, and scattered moderate elsewhere within 120 nm across the SE semicircle. Ulika has already begun to weaken earlier than previously forecast, as an upper level trough to the NW is imposing W to SW upper level wind shear, and also advecting dry and stable middle level air into the W and SW portions of the core circulation. This upper trough will continue to weaken Ulika during the next few days as it turns northward, then eventually decouples from the middle level circulation, leaving the low level remnant circulation to turn westward within 3 days as it remains embedded in the trade wind flow. 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 Depression Roslyn is centered near 21.0N 115.2W 1007 mb at 1500 UTC moving NE or 035 DEG at 9 kt. This is about 315 nm wsw of the southern tip of the Baja California Peninsula. Maximum sustained wind speed has diminished to 30 kt with gusts to 40 kt. Strong southwesterly upper level winds continue toproduce wind shear across Roslyn, with the low level center completely exposed, and convection occurring around the periphery of the circulation. Currently, scattered moderate to strong convection is occurring from 45 to 180 nm across the N quadrant, while scattered light to moderate convection is elsewhere from 45 to 150 nm across the N semicircle. Roslyn is forecast to continue to weaken further during the next few daysas it turns N and then NW and remains well offshore of Baja California. The remnant circulation is expected to 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 from Colombia near 10N74W to 10N93.5W to 11.5N107W to 07.5N119W...where it breaks...then resumes from near 13N117W to 14N135W. Isolated moderate convection is noted from 05N to 08N between 85W and 99W. Scattered moderate to strong convection is noted from 06N to 09.5N between 111W and 118W. Scattered moderate to strong convection is also observed within 240 nm of the Pacific coastline from 90W to the Mexican near 23N106W. ...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 to near 24N124W. 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 the weakening Roslyn continues northward, then nnw later tonight. 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 is expected across the Gulf of Tehuantepec tonight, increasing to fresh to strong flow on Thu, and then pulsing overnight 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 Roslyn dissipates, the pressure gradient will tighten around the subtropical ridge, with fresh anticyclonic winds expected between the monsoon trough/ITCZ and the ridge by Mon, with combined seas of 6 to 7 ft. The gradient will then relax some by the middle of next week. $$ Stripling