1. Recurring Weather

2. Objectives Vocabulary
Describe recurring weather patterns and the problems they create.
Identify atmospheric events that cause recurring weather patterns.
Vocabulary
drought
heat wave
cold wave
wind-chill factor

3. Floods
Floods can occur when weather patterns cause even mild storms to persist over the same area.

4. Northern California Sacramento River Flood
Malibu Landslides caused by Flooding and runoff…

5. Drought Droughts are extended periods of well-below-normal rainfall.
shifts in global wind patterns
allow large high-pressure systems to persist for weeks or months
over continental areas.

6. End of Section 3

8. HEAT WAVES
Heat waves, which are extended periods of above-normal temperatures, can be formed by the same high-pressure systems that cause droughts.

9. As the air under a large high-pressure system sinks, it warms by compression and causes above-normal temperatures.
-high-pressure system blocks cooler air masses from moving into the area, so there is little relief from the heat.

10. Heat Stroke & Heat Exhaustion
Heat Wave Dangers!!!
Heat Stroke & Heat Exhaustion
If the air is humid, it slows the rate of evaporation, which diminishes the body’s ability to regulate internal temperature.

11. Cold Waves
A cold wave is an extended period of below-normal temperatures.
Winter high-pressure systems are much more influenced by the jet stream than are summer systems and therefore rarely linger over one area.

12. Several polar high-pressure systems can follow the same path and subject the same areas to bout after bout of numbing cold.

14. Wind-chill factor
measured by the wind-chill index
estimates the heat loss from human skin caused by the combination of cold air and wind.

15. Section Assessment 1. What is the primary cause of a drought?
Recurring Weather
Section Assessment
1. What is the primary cause of a drought?
Droughts are usually the result of shifts in global wind patterns that allow high-pressure systems to persist for weeks or months over continental areas.

16. Recurring Weather
Section Assessment
2. What would the heat index be if the air temperature is 90ºF with a 60 percent relative humidity?
The heat index would be 100ºF.

17. Recurring Weather
Section Assessment
3. Which type of air masses are usually responsible for cold waves?
Cold waves are caused by air masses of continental polar or arctic origin.