Cyclones are large air masses characterized by low atmospheric pressure that rotate around a strong center, causing intense circular storms over warm tropical oceans. These storms are referred to as hurricanes in the Northern Hemisphere and typhoons in the Western Pacific. Examples include the Great Bhola Cyclone in Bangladesh in 1970, Haiphong Typhoon in Vietnam in 1881, and Hurricane Santa Ana in Puerto Rico in 1825. The devastating impacts of cyclones can be seen in events such as Hurricane Ida's repeated cycles of strengthening and weakening as it moved across a large area, and Cyclone Yasi causing widespread damage in Australia.