000 AXPZ20 KNHC 282205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2105 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... Tropical Storm Ulika is centered near 15.1N 138.7W 1000 mb at 2100 UTC moving N or 010 DEG at 6 kt. Maximum sustained winds have diminished to 50 kt with gusts to 60 kt. Water vapor imagery shows a broad upper trough just to the west and northwest of Ulika with its associated upper level southwest to west winds impinging on the cyclone. As a result, low-level cloud lines are becoming exposed in the western semicircle. Banding features have becomes less defined during the afternoon. Scattered moderate to strong convection is seen within 60 nm of the center, except within 30 nm of the center in the east and west quadrants. The 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 three 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 21.6N 115.2W 1007 mb at 2100 UTC moving N or 360 DEG at 6 kt, or about 304 nm west- southwest of the southern tip of the Baja California Peninsula. Maximum sustained winds have diminished to 30 kt with gusts to 40 kt. Strong southwesterly upper level winds continue to create south to southwest over Roslyn, with the low level center completely exposed, and convection well removed from the center within a distance from 60 to 150 nm in the north quadrant. The convection is of the scattered moderate to isolated strong type intensity. Roslyn is forecast to continue to weaken further during the next few days as it turns to the north and then to the northwest, and remains well offshore of Baja California. The remnant circulation is expected to gradually dissipate in about three 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 axis extends from Colombia near 10N74W to 10N85W to 11N100W to 12N107W to 06N117W...where it fractures. It then resumes from near 13N117W to 12N126W to 13N136W. Scattered moderate to isolated strong convection is noted 120 nm south of the axis between 101W and 104W, and also within 180 nm north and 120 nm south of the axis between 115W and 118W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sub-tropical ridge axis extends in a northwest to southeast orientation across the offshore zones west of the Baja California peninsula to near 24N126W. 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 west of 115W tonight, as weakening Roslyn begins to track to the northwest late tonight, then west-northwest on Friday. 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 northwest winds, and 5 to 8 ft seas west of the Baja California peninsula on Sun, and fresh to strong northwest winds developing Sun night. Fresh drainage flow is expected across the Gulf of Tehuantepec tonight, increasing to fresh to strong flow on Thu, and then pulse during the overnight hours 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 south to southwest flow is expected s of the monsoon trough through the upcoming weekend. Combined seas of 4 to 6 ft primarily in long-period southwest 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. $$ AGUIRRE