What produces hail from a tornado?

The tornado itself is not the cause of the hail. Hail is a phenomenon that occurs with thunderstorms that have strong updrafts. The hail forms as the updraft holds ice pellets aloft as layer after layer of supercooled water freezes to their surfaces. Eventually they become too heavy and fall out of the storm. The strongest updrafts are found in thunderstorms called supercells, which due to their rotation, are also the primary producers of tornadoes.