Recurring Weather

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

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

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

End of Section 3

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

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

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

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.

Cold waves can be caused by several polar air masses in a row

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.

Section Assessment 1.What is the primary cause of a drought? Recurring Weather

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

Section Assessment Recurring Weather 3.Which type of air masses are usually responsible for cold waves?

Section Assessment 1.What is the primary cause of a drought? Recurring Weather 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.

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

Section Assessment Recurring Weather 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 (jet steams or winter high pressure systems).

Problem Solving Lab Page 350