Increasing the ΔH threshold that defines a hail day makes it possible
to draw conclusions about the most intense events, as also proposed by
Witt et al. (1998). Convective cells with a larger vertical extent of the
hail growth zone can be expected to have an increased probability of larger
hail as well. The overall number of RHDs for the upper threshold of
ΔHN6 km presented in Fig. 4b is markedly lower compared with that
for a threshold of 3.5 km. The spatial distribution, however, remains similar,
aside from a few local maxima that vanish for the higher threshold,
for example those mentioned above between Erfurt and Magdeburg or
northwest of Berlin. In several regions, a large number of severe hail
days are still detected, for example in the area south of Stuttgart on
over 15 days. Small-scale maxima can also be found south and southwest
of Munich, in Rhineland-Palatinate, and in Hesse, here especially southwest
of Kassel. The agreement of the spatial distribution of RHDs using
the two different thresholds is another strong indication of the reliability
of the results obtained by the Waldvogel et al. (1979) criterion. Furthermore,
the finding also suggests that regions with the highest probability
of hailstorms on average are also exposed to the most severe storms.
This seemingly trivial result is not inevitably fulfilled given the dynamics
of long-living supercells or MCS that may affect hail hazard-prone regions
with the same probability as those in which hail rarely occurs.