 The wave continued westward and related thunderstorm activity increased during the following week . The convective system organized into Tropical Depression Twenty @-@ E on September 28 nearly midway between Mexico and Hawaii . Initially , the depression drifted toward the northwest due to a large upper @-@ level trough located to its west . Polo strengthened rapidly into a hurricane early on September 30 , with its winds peaking at 75 mph ( 121 km / h ) . Since the storm was very small , vertical wind shear caused significant weakening thereafter . On October 1 , Polo regained tropical storm strength as it was crossing into the north Central Pacific basin . It dissipated as a tropical cyclone later that day . There were no casualties or damages caused by Polo . 
