Viewer:

I noticed the sky was clear tonight except for a cloud formation in the eastern sky. It was interesting in itself, and then I saw lightning inside the cloud. It was lightning every minute or so and the cloud seemed to be stationary as I watched from my patio. It was very interesting and was wondering if you would explain it. Is this the same thing we used to call heat lightning when I was a kid in the sixties?

Nelson:

The thunderstorm you are referring to was on July 25th between 6 and 8:30pm.

This cell was a remaining thunderstorm cell that moved northward across EBR parish and into the Feliciana's about 8:00pm, while continuing to precipitate (rain) and weaken.

The phenomenon, known as heat lightning is a myth, perpetuated by an older generation that didn't understand the thunderstorm processes or life cycle.

First, the thought of this previous generation was that the excessive heat from the day was responsible for generating lightning usually during the summer when people enjoyed the longer days of summer. The fact is that all lightning is generated by thunderstorms, and that lightning is seen from a distance under darker skies at night ususally "in cloud" or "cloud-to-cloud lightning." The earth's curvature can actually allow the tops of thunderstorms to be seen for miles. The "lack of thunder" (or more properly, the distance in which sound will travel" is too great) to be heard. This is also in part due to the frequency of the sound that the lightning generates.

Here is an example, the faster a sound wave travels, the more distance it will cover in the same period of time. If a sound wave is observed to travel a distance of 700 meters in 2 seconds, then the speed of the wave would be 350 m/s. A slower wave would cover less distance - perhaps 600 meters - in the same time period of 2 seconds and thus have a speed of 300 m/s. Faster waves cover more distance in the same period of time.