Weather and ClimatePart 2 - Storms

CGF3MCrescent School

“When rain and thunder and lightning rumbled through the sky over ancient Greece, the people believed that Zeus, the celestial god of weather, was showing his anger with the mortals”

We all love warm sunny days, but we also must get clouds, rain, wind, snow etc.

Storms (Precipitation) occurs when air is cooled. Warm air rises, cools, condenses, forms clouds and it precipitates.

The way in which air is cooled is the theme for this slide show.

The question we should ask ourselves at this point is “How does air cool?”

Air can be cooled in three ways:

1.If air travels over a mountain it must rise. OROGRAPHIC PRECIPITAION.

2.Air in a localized area is heated to the point that the air around it is cooler. This heated air rises and is replaced by the cooler air. CONVECTIONAL PRECIPITATION

3. A large mass of air (air mass - large body of air that develops over a part of the earth’s surface and contains similar characteristics of temp. and precip.) collides with another air mass. This collision forces one air mass to rise above the other. The warmer air mass always rises above the cooler one.

CYCLONIC PRECIPITAION OR MID-LATITUDE STORMS OR FRONTAL

Clouds• Cirrus: high-altitude, wispy clouds associated with

warm fronts.• Stratus: grey, poorly defined clouds associated with

frontal precipitation• Nimbostratus: low altitude clouds associated with

frontal precipitation• Cumulus: fluffy, white clouds associated with fair

weather• Cumulonimbus: low-altitude, fluffy, grey, rain-

bearing clouds associated with thunderstorms.

Clouds are simply rising air!

CONVECTIONAL PRECIPITATION

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OROGRAPHIC PRECIPITATION

Orographic Patterns

FRONTAL PRECIPITATION

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• Bodies of air that develop over large areas of the earth’s surface.– Air must stay over source region for a long period

of time to take on characteristics of that region– Air must be stable

• Front: leading edge of an air mass• Eg. Cold Front or Warm Front

Air Masses

We will see this image again.

low pressure cell

cold front

warm front

S. Ontario

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Jet Stream

Powerful air currents in the stratosphere that influence the movement of storms. The Jet Stream flows from west to east (follows the rotation of the earth). The Jet Stream pushes the Westerlies in the same direction. All major storms over Ontario will generally flow from west to east. The Jet Stream also influences the position of the air masses that effect the North American continent.

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Air Masses affecting North America.

How does the Jet Stream play a role in this?

Lake Effect

Weather Forecasting

• Thermometers, rain gauges, barometers, wind vanes, etc.

• Weather stations are linked by GTS - Global Telecommunications System - supplies data from sources such as balloons, radar, and weather satellites.

Weather Forecasting

• Synoptic Charts/Weather Maps - plotted information recorded at weather stations– includes temperature, barometric pressure, wind

speed and direction, cloud cover, sky cover, dew point.

• Isobars: lines connecting places of equal atmospheric pressure.

• Front: leading edge of an air mass

Weather Forecasting

• Very popular with the media - 5 day forecast.• A lot of Technology is used on TV to show the

weather.• Why this importance over Weather

Forecasting?

Flash Corner:

Cyclonic Precipitation

Warm/Cold Front

THE END

GO TO THE THIRD AND FINAL PART - VIOLENT STORMS