Predictability of Eastern Mediterranean Cyclones: A Systematic, Process-Based Analysis of Upper-Level Potential Vorticity and Precipitation Features

The Mediterranean is a major cyclogenesis hotspot, where Eastern Mediterranean cyclones (MCs) play a central role in regional weather and climate. These systems are key drivers of precipitation and high-impact weather, including heavy rainfall and strong winds. However, their predictability remains limited due to complex topography and the interaction of multi-scale processes that are not fully resolved in numerical weather prediction (NWP) models.

This study investigates the dynamical controls on MC-related precipitation by linking the predictability of upper-level forcing to surface cyclone development and associated hazards. We analyze ~400 MCs over a 25-year period using ensemble reforecasts, with ERA5 as reference. Upper-level forcing is represented by potential vorticity (PV), while sea-level pressure (SLP) and precipitation characterize the surface response.

Forecast performance is evaluated using the feature-based SAL (Structure, Amplitude, Location) method, allowing a systematic object-oriented comparison of PV structures, cyclones, and precipitation across lead times. We present  case studies to illustrate the evolving link between PV, SLP and precipitation, and climatology of objectively tracked and classified cyclones, spanning different dynamical regimes from baroclinic systems to thermal lows.

Our results reveal a clear link between the upper-level PV structures and the predictability of surface cyclones and precipitation. Regimes associated with non-linear wave breaking exhibit reduced predictability, highlighting specific sources of forecast uncertainty. Furthermore, links emerge between the forecast skill of PV and SLP and that of precipitation for early lead time. These findings provide new, quantitative insight into the processes governing MC predictability and offer guidance for improving forecasts of high-impact weather in the water-sensitive Eastern Mediterranean.