Thunderstorm, Lightning & Hail - PP 5

How many people die from lightning strikes annually in Canada, according to the lecture, and during which months are deaths most common?

Approximately 9–10 people annually, with most deaths occurring during July and August.

What 2 factors influence which Canadian locations experience more lightning strikes?

Geography and climate.

What are the 2 stormiest regions of Canada?

Southern Ontario and the Southern Prairies.

Which Canadian city experiences the most thunderstorms, according to the lecture, and approximately how many per year?

Windsor, Ontario, with approximately 33 thunderstorms per year.

Approximately how many thunderstorms occur worldwide each year, and how many are active at any given moment?

Approximately 16 million thunderstorms occur annually, with around 2,000 active at any given moment.

Approximately how many thunderstorms occur in the United States annually, and what percentage become severe?

Approximately 100,000 thunderstorms each year, with about 10% reaching severe levels.

What 3 conditions can classify a thunderstorm as severe?

Hail measuring at least 1 inch in diameter, wind gusts exceeding 50 knots (57.5 mph), or the presence of a tornado. Only one condition is required.

What are the 4 types of thunderstorms?

Single-cell thunderstorms, multi-cell thunderstorms, squall lines, and supercells.

What are the 3 basic ingredients required for a thunderstorm to form?

Moisture, rising unstable air, and a lifting mechanism to push the air upward.

What can cause warm surface air to rise and begin forming a thunderstorm?

Heating from the sun and lifting mechanisms such as hills, mountains, or areas where different air masses meet.

Why does warm air continue rising during thunderstorm formation?

It remains warmer and less dense than the surrounding air, allowing it to continue rising.

Define convection in relation to thunderstorm formation.

The process of rising air transferring heat from Earth's surface to the upper atmosphere.

How do thunderstorm clouds form through convection?

Warm, moist air rises and cools, causing water vapour to condense into clouds that grow upward into colder, below-freezing air.

What are supercooled water droplets?

Liquid water droplets that remain unfrozen even though their temperature is below freezing, allowing ice particles to grow when they collect them.

How does the collision of ice particles contribute to lightning formation?

Collisions transfer electrical charges between ice particles, allowing large regions of electrical charge to build up inside thunderstorm clouds.

How is thunder produced during a thunderstorm?

Lightning generates sound waves in the atmosphere, which are heard as thunder.

What are the 3 stages of the thunderstorm life cycle, in order?

Developing stage, mature stage, and dissipating stage.

What happens during the developing stage of a thunderstorm?

Warm, humid air rises through updrafts, cools, and condenses into clouds, continuing to rise while warmer than the surrounding air.

What happens during the mature stage of a thunderstorm?

Large raindrops and ice become too heavy for updrafts to support, causing precipitation and downdrafts while updrafts continue bringing warm, moist air into the storm.

During which thunderstorm stage are hail, heavy rain, frequent lightning, strong winds, and tornadoes most likely?

The mature stage.

What happens during the dissipating stage of a thunderstorm?

Downdrafts dominate, warm and moist updrafts stop, rainfall weakens, and the clouds begin to evaporate.

How does a gust front contribute to the dissipation of a thunderstorm?

The gust front moves outward from the storm and cuts off the warm, moist air supplying the thunderstorm with energy.

What are the 5 main hazards associated with thunderstorms?

Lightning, hail, high winds, tornadoes, and heavy rain.

What is the definition of lightning?

A giant spark of electricity in the atmosphere that occurs between clouds, the air, or the ground.

Why do all thunderstorms produce lightning?

Thunder is caused by lightning, meaning every thunderstorm must contain lightning activity.

Why is lightning considered a significant natural hazard in Canada?

Lightning is a major cause of weather-related deaths during summer and one of the major causes of forest fires.

How frequently does lightning strike worldwide?

At least 100 times per second, nearly 9 million times per day, and more than 3 billion times annually.

Approximately how frequently does lightning occur in Canada?

Approximately 3 million lightning flashes annually, averaging about one every three seconds during the summer months.

How are Earth's surface and atmosphere electrically charged according to the lecture's description?

Earth's surface is described as negatively charged, while the atmosphere is described as positively charged.

How are electrical charges distributed within a thunderstorm cloud?

Positive charges generally accumulate near the top of the cloud, while negative charges accumulate near the bottom.

How do ice crystals contribute to the separation of electrical charges?

When ice crystals collide and fracture, smaller particles acquire positive charges while larger, heavier particles acquire negative charges.

What causes lightning to occur within thunderstorms?

An electrical current flows as areas with excess negative charges seek to balance with areas containing excess positive charges, releasing built-up electrical energy.

What are the 3 modes of lightning identified in the lecture?

Cloud-to-ground, cloud-to-cloud, and ground-to-cloud lightning.

What are 3 examples of tall objects that are particularly vulnerable to lightning strikes?

Trees, skyscrapers, and mountains.

Why are tall objects more vulnerable to lightning strikes, and are they always struck?

Tall objects are closer to storm clouds, reducing the distance lightning must travel through the atmosphere. However, they are not always struck because lightning depends on where electrical charges accumulate.

What are the 3 main areas affected by lightning strikes?

Humans, the engineered environment (buildings and infrastructure), and the natural environment.

What are 4 potential consequences of lightning strikes?

Human injury or death, infrastructure damage or destruction, forest and structural fires, and aircraft strikes.

How many people are killed or seriously injured by lightning annually in Canada, according to the lecture?

Approximately 10 people are killed and 125 people seriously injured annually.

When do most lightning casualties occur in Canada?

Approximately 75% occur between May and September, with July being the most lightning-prone month, and nearly 80% occur between 10 a.m. and 7 p.m.

What are the main lightning mitigation measures identified in the lecture?

Public awareness and education, lightning protection and grounding measures, building-code considerations, forecasting and monitoring, and related fire protection measures.

Do Canadian national or provincial building and electrical codes require lightning protection systems, according to the lecture?

No. The lecture states that installation is generally left to building owners, risk management advisors, insurers, and design professionals.

How can forecasting and monitoring reduce lightning-related impacts?

Forecasting and monitoring help identify potential lightning threats and support protective actions, including fire prevention and other measures addressing lightning consequences.

What is the definition of hail?

A form of precipitation consisting of solid ice that forms inside thunderstorm updrafts.

How do hailstones initially form?

Thunderstorm updrafts carry raindrops into extremely cold areas of the atmosphere, causing the droplets to freeze into hailstones.

How do hailstones increase in size?

They collide with liquid water droplets that freeze onto their surfaces, causing the hailstones to grow.

What causes hailstones to fall from a thunderstorm?

Hailstones fall when the thunderstorm's updraft can no longer support their weight, either because the stones become too large or the updraft weakens.

What is the approximate fall speed of small hailstones measuring less than 1 inch in diameter?

Approximately 9–25 mph.

What is the approximate fall speed of hailstones measuring 1–1.75 inches in diameter?

Approximately 25–40 mph, typical of hailstones found in severe thunderstorms.

What is the approximate fall speed of large hailstones measuring 2–4 inches in diameter?

Approximately 44–72 mph, often associated with the strongest supercell thunderstorms.

What are examples of people, animals, and property that can be harmed by hail?

People, livestock, aircraft, homes, cars, crops, and other property.

What are the 4 main consequences of hailstorms?

Crop damage, property damage, human injuries, and, rarely, death.

What are the 3 main hail mitigation measures identified in the lecture?

Public awareness and education, improvements and enforcement of building codes, and weather warning systems.