Assessing diabatic influences on extratropical cyclone development using complementary diagnostics

Extratropical cyclones are a key driver of midlatitude weather variability, including high-impact winter storms with heavy precipitation and severe wind gusts. Cyclone intensification results from the interplay of baroclinic dynamics and diabatic heating, the latter being closely linked to cloud-related processes within warm conveyor belts (WCBs). Focusing on European winter storms, this study investigates structural differences relevant for cyclone intensification between cyclones dominated by diabatic processes and those intensifying primarily through baroclinic mechanisms.

In a first part, we perform a systematic analysis of 247 winter storms affecting western and central Europe between 1979 and 2023, using a combination of a WCB diagnostic and the pressure tendency equation to quantify the diabatic contribution to cyclone deepening. Diabatic processes contribute on average 26.1% to cyclone intensification (median 25.3%), with cyclones exhibiting a relatively large diabatic influence (> 30.7%) showing steeper deepening rates, stronger northward displacement, enhanced precipitation, stronger wind gusts, and increased WCB activity compared to cyclones with a small diabatic influence (< 20.1%), despite similar minimum sea-level pressure. These cyclones are further characterised by warmer and moister WCB inflow conditions, favouring enhanced diabatic heating.

In a second part, we apply piecewise potential vorticity inversion to a limited number of representative cases as a complementary diagnostic to assess the methodological uncertainty in quantifying the role of diabatic processes. Together, these results demonstrate the benefit of combining complementary diagnostic approaches to better constrain the contribution of diabatic processes to extratropical cyclone intensification and highlight their potential for systematic evaluations of weather and climate models.