Distance criteria for safe operations when lightning is present

Many airports and other facilities curtail operations when cloud-to-ground (CG) lightning is within 5 nautical miles (nm). This criteria may not be adequate to safeguard lives for those working outdoors. For example, one person was killed and ten others injured in April 1996 when a single lightning flash struck a runway in Florida. At the time, the nearest thunderstorm was 7 to 10 nm from the airport. This flash occurred over 90 minutes after the previous CG flash within the warning boundaries. By examining the distances between CG lightning and thunderstorms, objective criteria for safe operations can be determined and applied to risk assessment. Initial results show that over 30% of CG lightning occurs at distances greater than 5 nm from a storm, making the above mentioned criteria inadequate.