Types of severe weather

How it affects us personally or socially, economically and environmentally,in this province,in this country andas part of the Northern hemisphere.

Types of severe weather Tornadoes Thunderstorms Floods Droughts Hurricanes Typhoons Tropical cyclones

Blizzards/Ice storms

Wind chill factor Temperature

inversion Monsoons El Nino La Nina

Tornadoespp. 585-588 Cause: Form in the most severe thunderstorms. Fast-

rising air in a thunderstorm begins spinning, forming a funnel of air and moisture, rising air causes pressure differences.

Effect: Massive destruction. Difference in pressure can lift roofs, cars, animals, trailer homes, etc.

Do? Deal with: make sure house is secure, be prepared, go in a basement or room in the centre of the house with no windows.

Thunderstormspp. 584-585 A storm with lightning, thunder, heavy rain and

sometimes hail. Cause: Uplift of warm moisture laden air – produces

high altitude cumulonimbus clouds – very unstable – high wind speed.

Deal with: Make sure windows, doors, etc. are secured, don’t go out in the storm if you don’t need to.

Floodspp. 589-590 Excess of water from rain, rivers, or occurs over land

that cannot soak up any more water. Two types: flash and broadside.

Effect: Destruction of property, house, etc. Some deaths.

Deal with: build dams on rivers/lakes, before expected heavy rains & snow run-off lower water levels in dams. Build spillways, floodways. Plant trees around rivers.

Droughtsp. 591 Natural events that occur whenever precipitation is

scarce over a long time. Areas around 30°N and S of the equator are high pressure areas where the average yearly rainfall is fairly low and are more likely to have droughts.

Effects: Soil dries out, cracks, crops wither, livestock die, farmers go broke.

Do? Prevent: Long-term planning helps reduce impact of droughts. In times of above average rainfall, don’t overgraze pastures, use water efficiently to prevent major shortages in future. Build reserves.

Hurricanes, Typhoons, and Tropical Cyclones

pp. 594-597 When cyclones near the equator become large

enough, they are classified as hurricanes, typhoons, or tropical cyclones.

Cyclones are low pressure systems that develop in the mid-latitudes when cold and warm fronts interact.

They are the same storm, given different names depending on the part of the world they are in.

Naming cyclones

Hurricane: Occurs in Western Atlantic, Caribbean Sea, Gulf of Mexico, Eastern Pacific.

Typhoon: Develops in Northwestern Pacific or China Sea.

Tropical Cyclone: Develops in Indian Ocean, Area around Australia.

The effect of these storms Massive destruction because high winds: boats, trees,

cars, shingles and other objects fly through the air crashing into buildings & killing and injuring people.

Storm surge – huge amount of sea water piled up by the intense winds and pushed onto the shore – can be 6 m high, tremendous damage as it flows inland & back out to sea.

Farther inland, most serious devastation is often caused by huge amounts of rainfall, often 50-60 cm/day – ground becomes saturated – can hold no more water.

Floods – mountainous regions even get mudslides.

What can we do? Reduce potential damage by boarding up windows,

reinforce buildings to withstand greater winds. Evacuate people inland to higher ground so they miss

storm surges & flooding. Store emergency rations of water, food, medical

supplies, camp-stove to boil water, etc. Listen to weather forecasts.

Blizzardspp. 598-599 When a warm air mass, filled with moisture moves

Northward and meets a cold Arctic air mass under a strong jet stream.

The resulting mid-latitude storm, rotating counterclockwise may drop up to a metre of snow in 24 h.

Also develop due to strong winds and the lake effect.

The effect of blizzards Effects: Devastating effects on transportation, cause

whiteout conditions on highways, roads, even on water, making driving dangerous, navigation on coast impossible with out radar. All travel becomes dangerous. Loss of electricity.

Do? Forecasters give enough time to prepare – stay off roads, bridges, stay in your vehicle if it gets stuck, don’t leave engine running, take blankets, extra warm clothes, food, matches, etc. Have enough supplies at home if power goes out.

Ice Stormspp. 600-603 Consists of freezing rain that usually lasts for a few

hours; A storm in which rain freezes on contact with the

surfaces it touches, forming a coat of ice. Warm air mass is pushed upward by cold air mass

below, moisture is warm air condense to form clouds & ice crystals, ice crystals fall through warm air mass – turn to rain – rain falls through cold air mass – cools & freezes instantly when it hits a cold object.

The effects of an ice storm Effect: Highways close, loss of electricity, no hot

water, no showers, no heat. Farmers suffer, elderly suffer (cold), pipes break when water freezes. Falling trees and branches cause damage.

Do? Listen to forecast, plan ahead, have sufficient supplies – food, medical, clothes, etc.

Heat wavespp. 604-605 A period of more than three days at or above 32°C. Heat waves in North America become more intense

when the Bermuda high, a sub-tropical high-pressure area in the Atlantic, extends over North America.

High pressure brings clear skies – allows more direct and intense solar heating of an already hot area.

Also caused by “temperature inversion” (see p. 604). Effect: dehydration, heat cramps, fainting, heat

exhaustion, heat stroke, death. Do? Stay out of sun, drink plenty of water, stop

exercising.

Temperature inversionspp. 604-605 When a layer of warm air in a high-pressure system

moves in and pushes down on cooler air. When this happens at lower altitudes, the cooler air

mass is trapped near the ground and it cannot rise as it becomes heated, thereby keeping the air near the ground humid and often polluted.

Effect: In over-populated areas, breathing becomes difficult, even hazardous, for some people. Pollution levels rise.

Do? Listen for air quality advisory or warnings.

Extreme cold (wind chill)pp. 606-607 Cold temperatures accompanied by brisk winds that

make it feel even colder. What temperature actually feels like with wind. Effect: Frostbite, hypothermia. Do? Stay inside heated buildings, wear lots of warm,

protective clothing, don’t expose skin.

Monsoonpp. 639-640 Seasonal winds that bring heavy rains in one season and

dry air in its other season. Caused by factors similar to cyclogenesis: upper-level

winds, including jet stream, influence cold & warm air masses at the surface.

Summer: low pressure systems above ground, heated air above land rises, replaced by moist air = heavy rains/floods.

Winter: dry, large high-pressure system over land, cooler than ocean, cause winds to blow from North/Northeast are dry/little moisture.

Do? Decrease deforestation, global warming.

El Niñopp. 612-614 A shift in the ocean currents, temperatures (water

becomes warmer), and atmospheric conditions in the tropical Pacific Ocean.

During El Niño, the warmer than normal water temperatures off the west coast of South America have a chain reaction effect, devastating plant and bird life and the local fishing industry.

La Niñapp. 614-615 A shift to cooler than average water temperatures and

atmospheric conditions in the tropical Pacific Ocean This effect is opposite to El Niño.

Severe weather occurrences

Will you be prepared?