Overall, the results of our calculations of the amplitudes of the
waves with m = 6, 7, and 8 in the field of the midlatitude meridional
velocity at 300 hPa suggest that 12 of the 17 HPA events during May − September of 2012 and 2013 substantially coincided or were
preceded by QRA events up to 2 wk earlier (see Fig. 1).