TI    < 25      no thunderstorm.
TI    25-34    potential of thunderstorms.
TI    35-39    potential of thunderstorms approaching severe.
TI    => 40    potential of severe thunderstorm.

Use the Index to determine the severity of thunderstorms.

Tests on the field (in the States) showed there is a good correlation between severe weather events and TI >40

Formula used: TI = KI - LI