Located to the south of a mid-level ridge, the depression moved to the west-northwest. With weak to moderate upper-level wind shear over the system, the depression gradually organized and intensified into Tropical Storm Erin on September 2. Though Erin had favorable upper-level outflow and developing convection, the inner core of the storm remained disorganized. The storm slowly strengthened, and attained an initial peak intensity of 60 mph (95 km/h) while located about 1,150 miles (1,855 km) east of the Lesser Antilles. Favorable conditions were expected to allow Erin to continue to strengthen to reach winds of 85 mph (135 km/h). However, an upper-level low to the northwest of Erin produced strong vertical shear over the storm, and Erin quickly weakened as the storm's low-level circulation center became exposed to the southwest of the deep convection. The shear slightly abated on September 4, allowing Erin to briefly re-strengthen. However, the storm remained disorganized, and following an increase in southwesterly wind shear, Erin began another weakening trend. On September 5, Erin weakened to a tropical depression, and hours later, the storm's low-level circulation dissipated.