Weather story or question?
Everyone in Victoria is talking about this morning’s thunderstorm! The rumble of thunder began just after 8 o’clock in my area of Saanich. I drove my son to school under dark, ominous clouds and upon reaching the parking lot, the thunder roared through the playground. All the kids were excited! Can’t say I blame them. The air was electric and sure enough, they witnessed a few flashes of lightning as the bell rang signalling the start of class. It was an impressive start to the day. I’m glad the teachers ushered them into class quickly. You know the saying, “when thunder roars, go indoors!”? There’s a good reason to heed the warning. Thunder and lightning go hand in hand and can be dangerous.
So what happened today? A low pressure area to the south (mostly over western Washington State and Oregon) brought a lot of moist unstable air to our area. That plus our warm, humid air made for a dramatic start to the day. In this type of situation, warm air rises, and condenses, creating the dark, towering cumulonimbus clouds. Water droplets within the cloud become supercooled and bounce around, colliding with each other. As they collide they become larger and electrically charged. Eventually the whole cloud becomes charged. Positive charges collect at the top of the cloud, while negative charges drop to the base of the cloud. Since opposites attract, positive charges collect beneath the cloud at the ground too. When the charges connect – zap! Lightning. Lightning takes the shortest route to the ground, so since positive charges collect at the tallest points (i.e. trees, buildings, cranes, etc.), those are first to be struck.
So what is thunder? It’s the sound you hear after a lightning strike. A lightning bolt is so hot, it causes the air around it to heat rapidly and expand. Thunder is the sound of that expansion. Because light travels faster than sound, you’ll see the flash before you hear the thunder. When you see the flash, start counting the seconds until you hear the thunder. That’ll tell you how many kilometers away the storm is from you.
Thunderstorms are responsible for a number of severe weather events. You may have noticed heavy rain in the Capital Region this morning. Sudden downburst winds are also often associated with thunderstorms. Severe storms can drop large hail stones and pour enough rain to cause flash flooding.
Thunderstorms typically form in areas that are warm, humid and damp which explains why there are so many thunderstorms near the equator. Here on Vancouver Island we average one day of thunderstorms every two years. It takes specific atmospheric conditions, and we had them this morning!
The low pressure system is expected to move northeastward into the southern BC by Friday pushing the bands of showers and thunderstorms into the southern interior in the next 24 hours. Environment Canada may issue rainfall warnings for some areas as forecasters predict heavy bursts of rain could amount to 50 millimeters!
Never a dull moment when it comes to weather!