Former Tropical Depression Nineteen-E strengthened to Tropical Storm Roslyn over the Eastern North Pacific Ocean south of Mexico on Thursday afternoon. At 5:00 p.m. EDT on Thursday the center of Tropical Storm Roslyn was located at latitude 15.5°N and longitude 103.0°W which put it about 180 miles (295 km) south-southwest of Zihuatanejo, Mexico. Roslyn was moving toward the west at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 1004 mb.
The government of Mexico issued a Tropical Storm Watch for the portion of the coast from Manzanillo to Cabo Corrientes.
Tropical Storm Roslyn strengthened gradually on Thursday afternoon. The inner end of a rainband wrapped around the eastern side of the center of Roslyn’s circulation. Other bands of showers and thunderstorms were in the eastern half of Tropical Storm Roslyn. Bands in the western half of the circulation consisted primarily of showers and lower clouds. Storms near the center of Roslyn generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 60 miles (95 km) in the northeastern quadrant of Roslyn. The winds in the other parts of Roslyn’s circulation were blowing at less than tropical storm force.
Tropical Storm Roslyn will move through an environment favorable for intensification during the next 48 hours. Roslyn will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the axis on an upper level ridge over the Eastern North Pacific. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. Tropical Storm Roslyn will strengthen during the next 48 hours. Roslyn could intensify to a hurricane by Friday night.
Tropical Storm Roslyn will move around the southwestern side of a surface high pressure system centered over northern Mexico. The high pressure system will steer Roslyn toward the west-northwest during the next 24 hours. On its anticipated track Tropical Storm Roslyn will move parallel to the southwest coast of Mexico during Friday. Roslyn will turn more toward the north when it reaches the western end of the high pressure system during the weekend. Roslyn could be west of Cabo Corrientes on Saturday night.