Original: The next morning, after passing over the state, Tropical Storm Katrina moved into the Gulf of Mexico, reintensified back to hurricane strength, and due to the warm waters of the Loop Current, began undergoing rapid intensification.
Simplified: The next morning, after passing over the state, Tropical Storm Katrina moved into the Gulf of Mexico, strengthened back to hurricane strength, and from the influence of the warm waters from the Loop Current, began undergoing rapid deepening.