premise: 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.
hypothesis: The first tropical cyclone that hit New York City is only known from recent research.
reason: The first cyclone was from pre-Columbian times and discovered by researchers from evidence in New Jersey. I think the system doesn't understand the vagueness of the sentence.