Because technologies such as Earth observation satellites were not available until the 1960s, historical data on tropical cyclones from the early 20th century is often incomplete. Tropical cyclones that did not approach populated areas or shipping lanes, especially if they were relatively weak and of short duration, may have remained undetected. Compensating for the lack of comprehensive observation and the limited technological ability to monitor all tropical cyclone activity in the Atlantic Basin during this era, research meteorologist Christopher Landsea estimates that the 1933 season may have produced an additional 2–3 "missed" tropical cyclones. A 2013 reanalysis of the 1933 Atlantic Hurricane Database did indeed identify two "new" tropical storms; however, it was also determined that two existing cyclones did not reach tropical storm intensity and so were removed from the database. Additionally, researchers found two existing storms to be one continuous system. As a result, the season storm total dropped from 21 to 20.