There were a total of twelve tropical storms during the season, five of which were unnamed. Of all the storms, four were hurricanes. Compared to the average activity from the previous two decades, the season's activity was below normal despite average sea surface temperatures and a normal number of tropical waves. Instead, the inactivity was the result of the subtropical ridge being located further south than normal, which decreased the atmospheric instability across much of the basin. Such a pattern was different from the more active 1954 and 1955 seasons. Several tropical depressions formed that did not attain tropical storm status, many of which formed beneath an unfavorable upper-level trough.