A Seven-Year Cycle?

The Perfect Storm 

Oct 28 - Nov 4, 1991

Hurricane Issac made its final landfall on the U. S. Gulf coast on Aug 29, 2012, seven years to the day after Hurricane Katrina.  Katrina made landfall on Aug 29, 2005 and was the single most destructive natural disaster in recorded U. S. history.  Katrina also killed more people than any other recorded storm except for the 1928 south Florida hurricane.  Oddly, Hurricane Sandy slammed into the Mid-Atlantic U. S. 2 months later during the 21st anniversary of the Perfect Storm of movie notoriety.  The Perfect Storm, a nor'easter that absorbed Hurricane Grace, never made landfall but it did cause deaths and damage in the northeastern as it battered the coastline.  It is particularly well known because of the 2000 film by the same name that chronicled the sinking of the Andrea Gail, a fishing vessel from Gloucester, MA.  Twenty one years later on Oct 29, 2012, Sandy made landfall as a category 2 hurricane but it was huge; over 1000 nautical miles. These odd coincide of anniversary and 7- and 21-year intervals has prompted some people to speculate about a seven-year cycle for catastrophic storms.  There is no scientific data to support the existence of such a cyclical pattern occurs, however.