Since most tornadoes are formed in conjunction with severe thunderstorms, forecasters first must determine where thunderstorms are likely to form and reach the severity necessary for tornado formation.
The difference between whether a thunderstorm will be severe with large hail and strong winds but no tornado, or whether a it will spawn a potentially deadly tornado is very subtle.
When evaluating areas for tornadic potential, forecasters traditionally examine observations and computer data to locate regions where strong instability and wind shear coexist.
However, recent research has begun to reveal tornado formation as an extraordinarily complex series of rapidly evolving storm-scale processes & events which occur below the resolution of current operational computer models.
While forecasters can determine areas where instability and wind shear might contribute to favorable tornadic conditions, NEXRAD Doppler radar is one of the best indicators of impending tornado formation.
By displaying swirling cloud-level winds that often precede a tornado, Doppler radar can help forecasters pinpoint areas where tornado formation may be occurring or is imminent. This can give meteorologists valuable lead time for the issuance of watches and warnings.