Toward the identification of different subcategories of medicanes

Although the definition of medicanes has been recently provided (Miglietta et al., 2025), the characteristics of the most intense among these cyclones have yet to be determined. This latter subcategory of medicanes includes cyclones that, during their mature phase, are driven almost exclusively by air-sea interaction and are responsible for the greatest damage.

In this context, we analyze 17 medicanes using ERA5 reanalysis data to study the role of upper-tropospheric processes in cyclone development. Using back-trajectory analysis, we investigated the presence of dry intrusions in the early and mature phases of cyclones. We found that the standard definition of a dry intrusion, characterized by a descent of 400 hPa in 48 hours, is rarely met. In contrast, weaker and shallower descents associated with PV streamers are more common. Although dry intrusions can accelerate warm core formation by promoting convection, the final intensity of the warm core depends critically on diabatic processes near the cyclone's center, as exemplified by Ianos.

In fact, in Ianos only marginal descending flows occur before the main tropical phase, yet this cyclone develops the most intense warm core among the analyzed cyclones. This prompted us to examine Ianos in detail using a WRF model simulation with a 3 km grid spacing. This simulation highlights the dominant contribution of diabatic heating to the cyclone's intensification already in the early stages and suggests a secondary role for the baroclinic forcing, indicating a different pathway in the cyclone's evolution. However, in the mature phase, a weak upper-level PV streamer contributes to the rapid deepening of the cyclone.