The 1821 Norfolk and Long Island Hurricane was one of four known tropical cyclones that have made landfall in New York City. Another, even more intense hurricane in pre-Columbian times (sometime between 1278 and 1438) left evidence that was detected in southern New Jersey by paleotempestological research. The third was the 1893 New York hurricane, and the fourth was Hurricane Irene in 2011.
There have been five other cyclones in New York City.
The scenario states that there have been four known cyclones. There may have been five total - that information is not known.