Observing mesoscale frontal convection and dry intrusions during NAWDIC using multi-dropsonde measurements

Mesoscale (~10–100 km) deep convection embedded within the cold-frontal region of extratropical cyclones (ETCs) can lead to high-impact weather. However, such convection remains poorly represented in operational weather prediction models. One key reason is the incomplete understanding of the mesoscale variability of thermodynamic and dynamic variables that leads to localized heavy precipitation associated with embedded deep convection. In particular, the dry intrusion (DI) airstream (characterized by descending cold, dry air from the upper troposphere) can either enhance or suppress embedded convection, highlighting the need for better constraints on its role in frontal dynamics.

The international field campaign North Atlantic Waveguide, Dry Intrusion, and Downstream Impact Campaign (NAWDIC), conducted during winter 2025/26, provides a unique observational perspective on these processes. In this contribution, we present airborne observations of mesoscale variability in frontal structures, with a particular focus on embedded convection and dry intrusions. Vertical thermodynamic and dynamic profiles are derived from a multi-dropsonde system, the “KITsonde” system, which captures mesoscale variability by simultaneously releasing up to four dropsondes with different fall velocity. These profiles are complemented by radiosonde soundings as well as wind and water vapour lidar measurements from a ground-based observation site at the Western Coast of France. The observed profiles are compared with corresponding profiles from weather prediction models using the KITsonde simulator, which predicts KITsonde trajectories and associated atmospheric properties from model data. Through the joint use of observations and simulations, we assess the ability of weather models to capture mesoscale variability associated with frontal convection in NWP models.