Tropical Storm Irwin formed over the Eastern North Pacific Ocean on Sunday. At 5:00 p.m. EDT on Sunday the center of Tropical Storm Irwin was located at latitude 17.2°N and longitude 121.3°W which put it about 835 miles (1315 km) west-southwest of the southern tip of Baja California. Irwin was moving toward the west-northwest at 10 m.p.h. (16 km/h). The maximum sustained wind speed was 40 m.p.h. (60 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 998 mb.

A low pressure system over the Eastern North Pacific Ocean west-southwest of Baja California strengthened on Sunday and the U.S. National Hurricane Center designated the system as Tropical Storm Irwin. The distribution of thunderstorms in Irwin’s circulation was asymmetrical. Most of the thunderstorms were occurring in bands in the southern half of Tropical Storm Irwin. Bands in the northern side of Irwin’s circulation consisted primarily of showers and lower clouds. The distribution of winds in Tropical Storm Irwin was also asymmetrical. Winds to tropical storm force extended out 60 miles (95 km) in the eastern side of Irwin. The winds in the western side of the circulation were blowing at less than tropical storm force.

Tropical Storm Irwin will move through an environment that is only marginally favorable for intensification during the next 24 hours. Irwin will move over water where the Sea Surface Temperatures are near 26°C. It will move under the southwestern part of an upper level ridge over the Eastern North Pacific Ocean. The ridge will produce northeasterly winds that will blow toward the top of Irwin’s circulation. Those winds will cause moderate vertical wind shear and the wind shear will inhibit intensification. There is also a region of drier air northwest of Tropical Storm Irwin. Tropical Storm Irwin could get a little stronger on Monday, but the vertical wind shear and the drier air will limit any intensification.

Tropical Storm Irwin will move south of a subtropical high pressure system over the Eastern North Pacific Ocean. The high pressure system will steer Irwin toward the west during the next few days. On its anticipated track, Tropical Storm Irwin will move toward the Central Pacific Ocean.