The 1947 Fort Lauderdale hurricane and Hurricanes Dog (1950), Easy (1951), Cleo (1958), Donna (1960), Ethel (1960) and Carla (1961) were all originally estimated to have Category 5 sustained wind speeds. However, later systematic studies by the Atlantic hurricane reanalysis project found that the wind speeds associated with these systems were overestimated and downgraded them to either Category 4 or 3. Most recently, Hurricane Iota (2020) was operationally considered to be a category 5 hurricane, with estimated 1-minute sustained wind speeds of . However, during their routine post-analysis best track process after the season, the NHC downgraded Iota to a Category 4 hurricane as a result of post season reanalysis, which suggested that there was a high bias in windspeeds derived from the Stepped Frequency Microwave Radiometer instrument.
