On the Development of Double Warm Cores in Intense Tropical Cyclones in the HWRF Model

This study examines the double warm core (DWC) structure in simulations of very intense tropical cyclones (TCs) using the HWRF model. It is shown that the DWC configuration is intimately related to a high level returning inflow confined within a thin layer right above the outflow level. This high level inflow brings the warm air from the lower stratosphere toward the storm center to form a high level warm core, thus lowering the TC mass center further and allowing for more potential energy to convert to kinetic energy. From the energy perspective, the warm air from the lower stratosphere acts like an extra source of enthalpy that helps TCs maintain their very strong intensity once TCs protrude sufficiently deep into the stratosphere. This study indicates the important role of the stratosphere in determining the potential maximum intensity of TCs that has not been examined previously. As such, variations in the stratosphere, either globally or locally, could result in long-term change of the TC climatology.