 Based on data from satellite imagery and weather reports from the cargo ships Hamburg Express and Aleksander Vermishev , the Eastern Pacific Hurricane Center ( EPHC ) upgraded a tropical disturbance into a tropical depression . At this time , the depression was located 390 mi ( 630 km ) west of Clipperton Island , a small remote island in the Pacific Ocean , at 1200 UTC July 16 . Moving towards the west beneath a high pressure area , the depression intensified into Tropical Storm Estelle 12 hours after formation . Upon being named sea surface temperatures along the storm 's path were 84 ° F ( 29 ° C ) , and thus Estelle began to rapidly intensify . The EPHC reported that Estelle had intensified a Category 1 hurricane on the Saffir @-@ Simpson Hurricane Scale on 1200 UTC July 17 , 24 hours after first forming . 
