A real estate agent uses the phrase, "location, location, location" to point buyers in the right direction. That same phrase is exactly the reason New Orleans is so vulnerable to getting hit by a major storm. It's the location, the warm wet low lands of the Mississippi Delta that makes New Orleans a magnet for hurricanes.
Hurricanes that impact upon the United States are formed in the east Atlantic Ocean at a time of year when the ocean water warms up. In an area off the coast of Africa between the Canary Islands and Cape Verde, atmospheric conditions impact with water temperatures to create a convection oven effect. A tropical wave of low pressure moves along the ocean surface with westerly winds. Air pressure drops at the surface of these storms, and this low pressure attracts warm moist air from the ocean's surface. The air spirals up off the water's surface and storm clouds form above it. A hurricane is just another name for tropical cyclone and that's a big storm packing fierce winds and heavy rains moving in a westerly counter-clockwise rotation. The twirling winds and thunderclouds form a circle around a central eye and gain intensity as the storm follows the warmer gulf stream waters in it's westward march over warm water toward North America.
Less than a century ago, hurricanes would arrive in the United States unannounced. They didn't have fancy names, just powerful winds, driving rains and a tidal wave storm surge. They would sneak up on us and make landfall with devastating destruction. Technology has given us radar and the ability to watch and track these storms from their formation to their arrival. In return, we've given them names. At one time, all hurricanes bore female names because someone thought the female of the species more unpredictable than the male and a hurricane was at the very least unpredictable. Today, they come with predetermined names, both male and female. Andrew hit South Florida. Katrina hit New Orleans. Once named, they gain notoriety. Once they hit land, they gain infamy.
Certain coastal areas in the Southeast United States are much more prone to hurricanes. This is primarily due to the phenomena of water temperature. The storm needs to feed itself with warm water as it makes its way west through the Atlantic. During hurricane season, from June through November, the gulf stream effect of the Atlantic Ocean provides that warmer water. Once formed, the storms move west toward the United States coastline following the route of the gulf stream waters. As the storm approaches the Western Hemisphere, the Caribbean Sea north from South America to the Antilles Island chain that includes Jamaica, Hispaniola and Puerto Rico, provides even warmer water. True, some storms will turn in the Atlantic and bear down on the Carolinas, or turn even further toward Bermuda, but the one predictable thing about a hurricane is its desire to sustain itself. That means feeding off the warmer water and the warmest water in this region can be found through the Caribbean Sea into the Gulf of Mexico. Having made that turn into the gulf, the storm is on a direct line into land somewhere between the Yucatan Peninsula and the Florida Panhandle. As the storm moves north through the gulf, Galveston, Texas and New Orleans, Louisiana are dead ahead.
Galveston has actually been hit more often by major hurricanes than New Orleans. But, Galveston is a barrier island that absorbs some of the impact of an approaching storm, while New Orleans is unique in its location. Built on a delta plain of sand and silt that has washed down from the Mississippi River over the centuries, approximately half of the city is under sea level. A system of levees, earthen walls, and pumping stations have been built to keep the city dry but, certain parishes in the city are already up to ten feet below sea level and continuing to sink every year. Technically, New Orleans is already under water, and it's warm water. As those major hurricanes enter the gulf, that's what they are looking for, warm water, and New Orleans provides just that.