As Hurricane Francine comes ashore, early this afternoon, her counterclockwise winds will pull copious amounts of rain in from the Gulf of Mexico. New Orleans lies in the projected path of that firehose and, unlike other coastal cities of the U.S., it lies below sea level.
Following the disaster produced by Hurricane Katrina, the city invested in a system of water pumps that are designed to handle up to 1 inch of rainfall per hour. Since Francine is currently "only" a Category 1 Hurricane, it is hoped that extensive flooding can be avoided; unfortunately, the soil of southern Louisiana is already saturated due to recent heavy rains, increasing the risk of flooding. Fortunately, the pumps are on their own power grid and will not be affected by more widespread power outages.
Nevertheless, landfalling tropical storms and hurricanes have recently over-produced when it comes to flooding. Warmer air and warmer sea water, the products of climate change, augment the humidity of the onshore flow and, should Francine slow down, the rainfall in NOLA could exceed the capacity of its pump network. We should know by later in the day.
