Chapter 11 HISTORICAL HURRICANE INFORMATION Goals: To investigate the historical record of hurricanes in the Atlantic Basin for the period 1886-1996, in the eastern Pacific Basin for the period 1949-1986, and in the western Pacific Basin for the period 1945-1991.

Data:

Lists and charts showing all hurricanes and tropical storms observed in the Atlantic Basin during the period 1886-1998, in the Eastern Pacific Basin during the period 1949-1998, and in the Western Pacific Basin during the period 1945-1998.

Procedure:

1. For each basin, graph the number of tropical storms and the number of hurricanes as a function of year (since the period of record is different for the various basins, you will not have the same starting and ending year for all basins). For the period 1961-1990, compute the average number of tropical storms and the average number of hurricanes per year in the western Pacific and eastern Pacific basins. How do these averages compare to the Atlantic Basin?

2. Do you see any times in the historical record (for any basin) when the frequency of tropical storms and hurricanes appears to increase to a new level of activity and then stays near that new level of activity in the years beyond? If so, can you suggest a reason(s) for the jump? Is it fair to say, without a caveat, that there are more hurricanes now than in the early to middle part of the 20th century?

3. It has been said that there are cycles in hurricane frequency. What decades appear to have been active hurricane decades in each basin? What decades were "lean"? Does an active hurricane season in one basin necessarily coincide with an active season in the other basins?

4. For the Atlantic Basin, graph the number of hurricanes that made landfall into the United States, as a function of year (use only the data for the period 1950-1998). Are we seeing more landfalling hurricanes in recent years?

5. On a map of the East Coast and Gulf Coast of the United States, plot the locations of landfalling hurricanes in the period 1950-1998. What regions have the greatest strike probabilities?

6. There is evidence that a link exists between the number of tropical storms and hurricanes that form in the Atlantic Basin in a given hurricane season and whether or not an El Nino is in progress. Using a table showing years when an El Nino / La Nina was in progress, determine the relationship between Atlantic Basin tropical activity and El Nino / La Nina.