000 AXPZ20 KNHC 291611 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Sep 29 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 16.7N 139.7W 1003 mb at 1500 UTC moving NW or 320 DEG at 6 kt. The maximum sustained wind speed is 40 kt with gusts to 50 kt. Currently, scattered moderate to strong convection is observed within 120 nm across the NE semicircle. Ulika continues to experience SW wind shear and is forecast to weaken to a tropical depression within 24 hours as it continues NW and crosses 140W and into the central Pacific. 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. Post-tropical cyclone Roslyn continues to slowly weaken over thefar offshore waters this morning, centered near 23.5N 115.5W,moving NNW at 6 kt. The upper level trough to the NW of Roslynthe past few days has sheared the middle level circulation awayfrom the low level center, which is entering southern Arizonathis morning. Only low clouds are left around the center ofRoslyn with light convection occurring within 75 nm NW of thecenter. Maximum winds are 25 kt with gusts to 35 kt, mainly Nthrough E of the center, where seas are to 8 ft. Roslyn is forecast to continue to spin down as a remnant low as it moves NW during the next 24 hours. 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 1010 mb low pres over Colombia near 09N74.5W to 12N106W to 09N120W to 1011 mb low pres near 13N133.5W, where it terminates. Isolated to scattered moderate to strong convection is observed within 60 nm N and 210 nm S ofthe trough between 97W and 115W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Post-tropical cyclone Roslyn is centered near 23.5N 115.5W, moving NNW at 6 kt, and producing seas of 6-8 ft in mixed swellacross the outer SW portion of zone PMZ013. To the NW of Roslyn, a sub-tropical ridge axis extends from nw to se across the offshore zones w of the Baja Peninsula terminating near 27N123W. Light to gentle n winds continue this morning W of the Baja Peninsula with seas 4-5 ft in mixed NW and SW swell. Theridge will strengthen and build SE during the next few days, and Roslyn dissipated, and gradually produce a moderate to fresh nw flow, with 5 to 8 ft seas across the the northern two- thirds of the Baja Peninsula on Sun. Light and variable winds are expected through the weekend across the northern Gulf of California, and light to gentle nw-n flow is expected elsewhere. Winds will increase through mid week as the ridge builds into the region. A high amplitude surface trough analyzed from 12N106W to 20N107W, and is expected to continue to drift w over the next day or so. Active convection is occurring this morning in an inverted vee pattern, around the periphery of this trough. Isolated to scattered moderate to strong convection is from 12N to 20N between 101W and 113W, and scattered moderate to strong convection extends to the north from 20N to 24.5N east of 1`09W to the Mexican coast. Fresh to strong drainage flow has developed across the Gulf of Tehuantepec overnight and will continue to pulse up and downthrough the weekend, peaking near 25-30 kt with seas of 8-10 ft late at night through sunrise. 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 4 to 7 ft, primarily in long-period SW swell is expected across the offshore waters through the upcoming weekend. REMAINDER OF THE AREA... As tropical cyclone Ulika moves w of 140W this afternoon through tonight and tropical cyclone Roslyn dissipates, the pressure gradient will tighten around the subtropical ridge, with moderate to fresh anticyclonic winds expected between the monsoon trough/ITCZ and the ridge through early next week, with combined seas of 5 to 7 ft. The gradient will then relax some by the middle of next week. $$ Stripling