 As early as 1957, it was recognized that an increasing trend in the number of tropical cyclones each season in the Atlantic Basin was at least partially tied to increasing observations and better records.By analyzing the density of ship tracks over time, it has been estimated that between 1900 and 1966, an average of two storms per year are missing from HURDAT.This is mainly due to a lack of satellite imagery and lack of reconnaissance aircraft prior to 1943.