Each year, tropical cyclones and hurricanes leave millions homeless worldwide and account for, on average, over $100 billion of damage in the United States alone [Schmidt et al., 2009]. In 2005, a record- breaking 15 hurricanes formed in the North Atlantic, four of which reached category 5 strength. Over the course of that season, more than 3000 hurricane-related deaths occurred and fiscal damage reached $157 billion.
Because a better understanding of when and where tropical cyclones and hurricanes will form and strike will help societies better prepare for adverse effects, improving the understanding of these storms is very important. In the Western Hemisphere, tropical cyclones can form and develop in both the tropical North Atlantic and eastern North Pacific oceans, which are separated by the landmass of Central America. From the point of view of large-scale atmospheric circulation and its influence on tropical cyclones [e.g., Bell and Chelliah, 2006], it is not surprising that tropical cyclone variabilities in these two basins are related, because of their geographic proximity. But several questions remain: How they are related? What physical mechanisms drive this relation?