Severe Weather Types
In Nova Scotia, we can face a number of severe weather events. All can lead to injury or loss of life, property damage, and loss of essential services.
Heavy Snowfall and Blizzards
Winter storms with winds exceeding 40 km/h (25 mph), with visibility reduced by falling or blowing snow to less than a kilometre and lasting for at least three hours.
Risks: Treacherous travel conditions; loss of essential services
Frozen precipitation consisting of balls or irregular lumps of ice called hail stones.
Risks: Property damage; treacherous travel conditions; loss of essential services
Violent or Heavy Rain
When the precipitation rate is between 7.6 millimetres (0.30 in) per hour and 50 millimetres (2.0 in) per hour, rain is considered heavy. Rain is considered violent when the precipitation rate is greater than 50 millimetres (2.0 in) per hour.
Risks: Flash flooding; localized flooding; contaminated food; electrocution from submerged electrical sources.
Hurricanes and Tropical Storms
“Hurricane” comes from the Carib Indian word “huracan” which means “evil wind”. They are fierce, rotating oceanic weather systems that form and intensify over tropical ocean regions. Hurricanes have sustained winds exceeding 118 km/hr (74mph) and produce massive waves, torrential rains, and floods. A Category 1 storm has the lowest wind speeds, while a Category 5 hurricane has the strongest. Lower category storms can sometimes cause greater damage than higher category storms, depending on where they strike and the particular hazards they bring. Tropical storms are systems of strong thunderstorms with sustained winds of 62 -117 km/h (39-73 mph). On average, eleven tropical storms develop annually over the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. About half of these storms become hurricanes. All such storms have names.
Risks: Storm surges and dangerous seas; flooding and fast moving waters; loss of life or damage to property from high winds and falling or projectile objects; contaminated food from flood or surge waters; electrocution from submerged electrical sources; treacherous travel conditions; loss of essential services.
Ice Storms with Freezing Rain
Winter storms, characterized by freezing rain, that result in at least ¼ inch of ice on exposed surfaces. The precipitation from these storms covers everything with smooth glaze ice. Just one quarter of an inch of ice accumulation can add about 500 pounds of weight to a typical utility line span.
Risks: Treacherous travel conditions; loss of essential services for extended periods of time from downed lines, trees or other fallen objects
Thunder and lightening storms
Thunderstorms are often accompanied by high winds, hail, lightning, heavy rain and tornadoes. Lightning occurs when the air becomes charged with electricity during a thunderstorm.
High Winds and Les Suetes
Les Suetes are southeasterly winds created when a frontal inversion causes a funneling effect over the Cape Breton mountains. As the winds rush down the side of the highlands, strong gusts can exceed 150 km/h (94 mph).
Risks: Death, injury or damage to property from toppled objects, projectiles, force of wind; loss of essential services from downed lines or trees; dangerous seas
A storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Storm surges are produced by water being pushed toward the shore by the force of the winds moving cyclonically around the storm.
Risks: Coastal flooding, danger to life from being swept out to sea; electrocution from wet electrical components; food contamination; dangerous seas.
Wildfires are uncontrolled fires in the countryside or wilderness area. They differ from other fires by size, the speed at which they can spread, their potential to change direction unexpectedly, and their ability to jump gaps like road and rivers.
Risks: Injury, loss of life, damage to property from fires and smoke.
Large, ferocious storms with strong areas of low pressure and centres of rotation that form off the East Coast of North America. These storms travel to the northeast from the south with the winds coming from the northeast and can bring severe rain or snowfall. Typical conditions include heavy rain or snow and coastal flooding, coastal erosion, severe winds, storm surges,
Risks: Loss of essential services; danger to life from being swept out to sea; electrocution from wet electrical components; food contamination.
Heat waves are produced by static high pressure areas that cause prolonged periods of excessively hot weather. They may be accompanied by high humidity.
Risks: Wildfires; dehydration; heat exhaustion and stroke; heat-related death; power outages from overloaded grids; damage to roads and highways; burst water lines.