The strongest cyclone of the 1977 season began as a tropical disturbance over the open eastern Pacific. It developed into a tropical depression around 12:00 UTC on September 20 and strengthened into Tropical Storm Florence twelve hours later. The newly formed system moved west-northwest until reaching hurricane strength by 00:00 UTC on September 22, at which point Florence sharply curved toward the north-northeast. With a well-defined eye on satellite imagery, the storm reached peak winds of around 18:00 UTC on September 22, a Category 2 hurricane. Florence accelerated over increasingly cool ocean temperatures, causing it to weaken to a tropical storm early on September 23, weaken to a tropical depression early on September 24, and transition to an extratropical cyclone by 12:00 UTC that day.
