 On September 26, ship reports and satellite imagery indicated an area of squally weather about 300 miles (485 km) south of Guatemala. During September 27 and September 28, the disturbance moved westward. On September 29, the disturbance developed a closed low-level atmospheric circulation. The following day, the system was designated as a tropical storm after a ship reported winds of 45 mph (70 km / h). A Hurricane Hunter aircraft investigated the growing storm on October 1 and estimated maximum sustained winds of 75 mph (120 km / h), making Joanne a Category 1 hurricane. However, very few ships reported winds greater than 30 mph (50 km / h) at that time. On October 2, the Eastern Pacific Hurricane Database, noted that the hurricane had intensified into a Category 2 system, with winds peaking at 100 mph (160 km / h) while turning towards the northwest.
