I was always a spectator rather than a participant when it came to science fairs in school. My only memory of actively contributing to anything that resembled a science project came in the 7th grade. What attracted me I suspect was how easy it was: demonstrating how far away a thunderstorm was by visual detections of lightning strikes. I suppose I benefitted from this endeavor because it has always stayed with me and now, you the reader, will have the benefit of this wisdom.
Using the information of mach speed we can not only determine how far away a storm is but pretty much determine if it is coming our way or heading in the opposite direction. Mach speed is the tag given to the speed of sound. Those of you old enough to remember are probably familiar with this term during the 1950’s when test flight’s of the X-1 jet would make an explosion overhead referred to as a “sonic boom” as they raced across the skies at Mach I speeds (Mach II refers to twice the speed of sound). Later in the decade design changes in the aircraft would eliminate this annoying sound.
But I digress. Mach I (the speed of sound) is registered at 768 miles per hour (1,236 km/h), or approximately one mile in five seconds (roughly one kilometer in three seconds). Since we see the lightning flash before we hear it, it’s obvious that light travels faster than sound. Light travels at about 186,282 miles per second (299,792,458 metres per second) making it essentially instantaneous for the human eye. If we measure in seconds from the visual point of lightning until we hear the thunder we will know relatively well how close or far away the storm is.
By adding up the seconds and dividing them by 5 (3 where the metric system is standard) we can determine the distance of a storm. If you don’t have a watch or a timing app on your I-phone, you can manually measure the distance by counting at a rate that gives you some measure of accuracy. The manual method I learned was to count saying “1-Mississippi, 2-Mississippi, 3-Mississippi …. etc.” at a normal cadence. Measure your counting cadence one time when in front of a clock second hand to get a feel for what your “normal” is.
You’ll know if the storm is approaching if the amount of time continues to decrease or receding if the mount of time increases. Audial clues will also help with your evaluation as the thunder increases and decrease in volume. If the times remain mostly constant for a lengthy period it is possible that the storm is moving perpendicular to you. Visually determine wind direction to assist you with this by watching the movement of the clouds.
You may have not been a geek in school and the physical sciences may not be your forte, but some things in nature are simply not that difficult. If you have reached this point in your reading you are now aware, if you weren’t before, how to measure storm speed in layman’s terms; at least the kind that includes some thunder and lightning. Go forth now and impress your friends and neighbors.
I see the bad moon arising.
I see trouble on the way.
I see earthquakes and lightnin’.
I see bad times today. – Credence Clearwater Revival
