tornado fujita scale

air alert alley america atmosphere atmospheric bad black city climate cloud clouds cumulonimbus cyclone damage danger dangerous dark debris destroy destruction destructive forecast forecasting front fronts fujita funnel hurricane low meteorology pressure rain rainstorm rate rating scale science sciences scientific season skies sky squall storm storms strong supercell threat threatening thunderstorm thunderstorms tornado tornadoes town twister twisters twisting violent vortex warning weather whirlwind wind winds windy