A case study of a subsynoptic disturbance in a polar outbreak

Abstract

A subsynoptic disturbance, occurring in an outbreak of polar air over northwestern Europe, is studied by using routine observational data. The disturbance showed a characteristic length scale of about 150 km, a time scale of 4 hours, caused a surface pressure drop of only 1 mb, but brought up to 20 mm of precipitation in the coastal region of the Netherlands. The observational analysis suggests that the disturbance was a warm-core system driven by latent heat release and triggered by forced lifting along the coastline, which activated a weak trough filled with potentially unstable air.