Summer in North America is storm season. Thunderstorms bring lightning, strong winds, heavy rain and of course thunder. Memories of summer storms range from watching the lightning flash across the sky on a hot humid night to children (and even some adults and their pets) hiding under their beds waiting for the storm to pass. There are many different explanations for thunderstorms, like the man in the moon is bowling or the Gods are angry about something, but what really causes a thunderstorm and what can be done to stay safe?
Thunderstorms are caused by warm air rapidly rising. As the warm air reaches the cooler atmosphere the air’s temperature drops and starts to condense into cumulonimbus clouds. Eventually the warm air reaches its dew point and turns into water droplets. The water droplets start to fall back to the ground, but along the way they collide with other droplets and get even bigger. The large amount of cool rain falling back creates a strong downdraft of cool air which causes the strong winds and temperature drop that often accompany or precede a storm.
The actual cause of lightning is still debated among scientists. The most common belief is that basically, friction from ice droplets in the clouds cause a charge of static electricity to build up within the cumulonimbus cloud as it moves across the warmer ground.
Eventually the electrical charge within the cloud will become large enough that it must discharge, and the result is a gigantic spark which conducts the electrical energy to the ground. The resulting flash from the spark is known as lightning. Lightning that discharges from cloud to ground is often referred to as fork lightning and is the most dangerous. The static charge can also be discharged to another cloud in the atmosphere. When this happens it is known as cloud to cloud, sheet or heat lightning.
Thunder is the noise the spark makes as it passes through the air. The spark causes the air along its length to be superheated to over 20,000 °C (36,000 °F) causing a shockwave which can be heard for several miles.
Lightning and thunder happen at the same time, but since sound travels slower than light they often appear as separate phenomenon. A flash followed by thunder 3 seconds later is approximately 1KM away from you. A flash followed by thunder 5 seconds later is about a mile away. If they both happen simultaneously then the storm is right above you and it is definitely time to seek shelter!
If you are caught in a storm there are a few things you can do. When at home, turn off and unplug TV’s, radios, computers and corded telephones. Also, avoid using showers and sinks. Lightning strikes can cause surges in power lines frying your household electronics and if electrical lines are grounded to your plumbing, then anyone touching running water could be electrocuted too. Try to avoid rooms with large windows as the glass could break during the storm.
If you are caught driving in a thunderstorm, remain in your vehicle. The tires should insulate your car from a lightning strike. If the storm becomes severe enough pull over in an area away from tall trees and objects and wait the storm out. Avoid being the tallest point in an isolated area-lightning tends to hit the tallest object.
If you are unlucky enough to be outside on foot when a severe thunderstorm hits, seek shelter in a building or your vehicle as soon as possible. Stay low to the ground and avoid areas such as under tall trees and picnic shelters, gazebos, or other isolated and tall objects. Avoid being on hillsides or high ground, areas with water lying or accumulating in them, and open spaces. If you are out on the water in a boat or canoe, get to shore as soon as possible and seek shelter.
Although lightning rarely strikes open water the heavy rain fall and winds associated with a thunderstorm could overwhelm your boat very quickly. Hiding in low lying areas such as a ditch can be dangerous if there is flash flooding so be prepared to move to another location should the one your are in start to fill up with water.
Thunderstorms are one of nature’s most magical and powerful shows. This summer when the storms start, know how to stay safe and prepare to sit back and watch the show rather than hide with your pets under the bed.
Copyright 2019 Mike Wilson
