Shows figure by Blanchard et al. indicating areas where weak inertial stability or inertial instability might lead to upscale growth of convection by enhancing the upper level divergence. One of the reasons why frontal and mesohigh type events often form near the axis of an upper level ridge may in part be due to the weak inertial stability found near the ridge. Region where there is strong anticyclonic curvature or anticyclonic shear are places where the inertial stability is weak.