 This system moved generally to the east @-@ northeast throughout its life cycle . Forming near Hainan Island on May 21 as a monsoon depression , the initial tropical disturbance moved through the South China sea while slowly organizing . Becoming a tropical depression in the Formosa Strait , Mac quickly became a tropical storm and turned northeast , paralleling the coast of Taiwan . On May 27 , Mac turned back towards the east @-@ northeast as upper level westerly winds increased , causing vertical wind shear which led to Mac weakening into a tropical depression before dissipating on May 29 . 
