 A tropical wave moved across the northeast Pacific Ocean and formed a tropical depression south of Mexico on October 16 . It strengthened at a moderate pace and reached hurricane intensity on October 18 . Trudy entered a favorable environment and explosively intensified , reaching its first peak in strength on October 20 . At that time , an upper @-@ level trough drifted Trudy north , which increased vertical shear , causing it to substantially weaken the system back to Category 1 hurricane status . The trough <unk> the storm and was replaced by a ridge which turned the storm back to the west and led to its re @-@ intensification to a Category 4 hurricane . Another upper level trough approached which pulled Trudy northward once again , and <unk> the hurricane apart . The cyclone dissipated on November 1 . Eventually , some of its moisture spread over parts of Mexico and the United States . 
