The Role of Diabatic Processes in Jet Streak Intensification over the North Atlantic during a Serial Cyclone Cluster event encompassing storms Dudley and Eunice

Serial cyclone clustering is commonly associated with intensified upper-level jet streaks and enhanced baroclinicity. While both diabatic processes and double-sided Rossby wave breaking have been proposed as explanatory mechanisms, their relative contributions remain incompletely understood. This study introduces a jet-streak-centered visualization technique to quantify contributions to cross-jet heating and to analyze the lifecycle of a jet streak that was pivotal during the development of the cyclone cluster consisting of the severe windstorms Dudley and Eunice over the North Atlantic in February 2022. The analysis relies on numerical simulations conducted with the Open Integrated Forecasting System developed by the European Centre for Medium-Range Weather Forecasts (ECMWF).

For the selected case study, the initial intensification of the jet streak along the North American East Coast appears to be primarily driven by diabatic processes. Specifically, latent heat release on the equatorward side and upstream of the jet streak maximum serves to strengthen the horizontal temperature gradient, thereby via the thermal wind law reinforcing the upper-level jet streak.

Furthermore, sensitivity experiments varying the magnitude of latent heat release demonstrate a significant impact on jet strength: a reduction in latent heat release (50% L_v) yields a substantially weaker jet streak, whereas an enhancement (150% L_v) results in a marginally stronger jet streak compared to the control run. The evolution of baroclinicity, diagnosed via the Eady growth rate, proves more complex, appearing to stem from an interplay between vertical wind shear and atmospheric stability. Under conditions of reduced latent heating, stability decreases, yet this does not offset the significantly weakened vertical wind shear. Conversely, with increased latent heating, stability is enhanced, acting to suppress baroclinicity despite the presence of strengthened vertical wind shear.

We conclude that latent heat release is the dominant mechanism driving the initial intensification of the jet streak during this February 2022 serial cyclone clustering event, indicating that diabatic processes play a central role in shaping the baroclinic environment of such cyclone clustering events.