Hail in a Thunderstorm
At times, the cumulonimbus clouds in a very severe thunderstorm produce hail also. Because of the great vertical extent of the cumulonimbus and the co-existence of ice- crystals with the water particles, the necessary conditions are present for hail formation. But not all cumulonimbus clouds produce hail.
For hail formation, besides the high water content of clouds, the temperature lapse rate should also be very steep so that buoyancy of cumulous updrafts is the largest to provide an opportunity to hailstones to increase their size.
Maximum ground heating in the afternoon provides ideal conditions for hail formation. Topography is an additional determining factor of the pattern of a hail. The size of a hail is determined by the rate of uplift within a cumulonimbus cloud and its high water content.
Even though there is a close relationship between thunderstorms and hail formation, there does not appear to be a positive co-relationship between the two. For example, in spite of numerous thunderstorms in the tropical regions the occurrence of hail is quite uncommon.
In regions where the occurrence of hail is more frequent, the precipitation-initiation level is characteristically higher than in the more humid regions.
