Now, a recent study in Physical Review Fluids has used simulations to explore the fate of landfalling hurricanes. The scientists found that after landfall, the warm, dynamic heart of a hurricane is replaced by a growing cold core – an unexpected finding that could help forecasters predict the level of extreme weather that communities farther inland may face.
“Generally, if a hurricane hits land, it weakens and dies,” said Professor Pinaki Chakraborty, senior author and head of the Fluid Mechanics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST). “But sometimes, a hurricane can intensify again deep inland, creating a lot of destruction, like flooding, in communities far away from the coast. So, predicting the course that a hurricane will take is crucial.”
These re-intensification events occur when hurricanes, also known as tropical cyclones or typhoons in other global regions, transition into extratropical cyclones: storms that occur outside the Earth’s tropics. Unlike tropical cyclones that harness their strength from ocean moisture, extratropical cyclones gain their energy due to unstable conditions in the surrounding atmosphere. This instability comes in the form of weather fronts – boundaries that separate warmer, lighter air from colder, denser air.
“Weather fronts are always unstable, but the release of energy is typically very slow. When a hurricane comes, it can disturb the front and trigger a faster release of energy that allows the storm to intensify again,” said first author Dr. Lin Li, a former PhD student in Prof. Chakraborty’s unit.
However, predicting if this transition will occur is challenging for weather forecasters as hurricanes must interact with this front in a specific and complex way. Currently, forecasters use one key characteristic to objectively identify this transition: the presence of a cold core within a landfalling hurricane, caused by an inward rush of cold air from the weather front.
