Ida maintained its strength well inland despite its slow movement due in part to a phenomenon called the Brown Ocean Effect. Its when tropical storms that normally weaken over land either maintain their intensity or strengthen due to the combination of high moisture and heat content over the area the storm passes. The high moisture and heat content over these land areas can mimic the type of environment that a hurricane or tropical storm would experience over a warm body of water. Evaporation leads to condensation, which leads to a release of latent heat. This latent heat is the primary driver of these tropical systems by lowering the surface pressures and strengthening the storm.
This is what happened with Ida on Sunday with the storm traveling well inland as a Category 4 some 4 hours after landfall. It was still a Category 3 after nightfall west of New Orleans. Despite its slow movement, the storm was able to maintain this intensity as a result of it moving over the Mississippi River and Atchafalaya Basin . This is a marshy area and contains a high amount of moisture & heat content despite its shallow nature. Similar storms such as Hurricane Andrew (Everglades) in 1992 and Tropical Storm Fay (Glades Co) in 2008 have exhibited similar behavior while moving across South Florida's, marshy landscape. Perhaps the most striking example was Tropical Storm Erin over central Oklahoma in 2007. The storm moved over a highly moist area northwest of Oklahoma City and the storm regained tropical storm status and even developed an eye...HUNDREDS of miles from the Gulf.
Research is still preliminary but there have been several documented cases of the Brown Ocean Effect playing a role in the re-intensification of tropical systems.
FOX 4 CHIEF METEOROLOGIST DEREK BEASLEY