science ~ chapter 8 weather
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Science ~ chapter 8 weather. Miss Nelson. Section 4. Storms. Anticipatory set. What are the four types of fronts? What happens when air masses with different pressure and humidity meet?. standards. S 6.4.e – - PowerPoint PPT PresentationTRANSCRIPT
What are the four types of fronts?
What happens when air masses with different pressure and humidity
meet?
ANTICIPATORY SET
S 6.4.e –Students know differences in pressure, heat, air movement, and humidity result in change in weather
STANDARDS
Storm – a violent disturbance in the atmosphere
Thunderstorm – a small storm with heavy precipitation and frequent thunder and lightning
Lightning – a sudden spark, or energy discharge, caused when electrical charges jump between parts of a cloud, between nearby clouds, or between a cloud and the ground
KEY TERMS
Tornado – a rapidly whirling, funnel-shaped cloud that reaches down to touch Earth’s surface
Hurricane – a tropical storm that has winds of about 119 kilometers per hour or higher
Storm surge – a “dome” of water that sweeps across the coast where a hurricane lands
KEY TERMS
Storms involve sudden changes in air pressureIn turn cause rapid air movements
Conditions that bring one kind of storm often cause other kinds of storms in the same areaConditions that cause thunderstorms can also cause tornados
STORMS
Most cumulonimbus clouds form on hot, humid afternoons
Also form when warm air is forced upward along a cold front
Many thunderstorms form in the spring and summer in southern states or on the Western Plains
HOW THUNDERSTORMS FORM
During a thunderstorm areas of positive and negative electric charges build up in the storm clouds
Lightning is a sudden spark, or electric discharge, as these charges jump between parts of a cloud
Similar to the shocks you sometimes feel when you touch a metal object on a dry day… but on a MUCH larger scale!
LIGHTNING AND THUNDER
A lightning bolt can heat the air near it to as much as 30,000 degrees Celsius MUCH hotter than the sun’s surface
The rapidly heated air expands suddenly and explosively
Thunder is the sound of the explosion
Because light travels faster than sound, you see lightning before you hear thunder
LIGHTNING AND THUNDER
Can cause severe damage
The heavy rains associated with thunderstorms can flood low-lying areas
Lightning strikes can shatter tree trunks or start forest fires
When lightning strikes a person it is like a powerful electric shock
Can cause burns, unconsciousness, or even heart failure
THUNDERSTORM DAMAGE
During thunderstorms, avoid places where lightning may strike
Also avoid objects that can conduct electricity, such as metal objects and bodies of water
THUNDERSTORM SAFETY
One of the most frightening and destructive storms
A rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch Earth’s surface
If it occurs over a lake or ocean it is known as a water spout
Are usually brief May touch the ground for 15 minutes or less
Only a few hundred meters across
Wind speeds may approach 500 kilometers per hour
TORNADOES
Tornados most commonly develop in think cumulonimbus clouds
The same clouds that bring thunderstorms
HOW TORNADOS FORM
Are most likely to occur in spring and early summerin late afternoon when the ground is warm
The Great Plains have the kind of weather pattern that is likely to create tornadosWarm, humid air mass moves north from the Gulf of Mexico into the lower Great Plains
A cold, dry air mass moves south from Canada
HOW TORNADOS FORM
Tornados are rare in California
About 800 occur in the United States every year
View figure 21 on page 321 of your textbook
TORNADO ALLEY
All year round, most precipitation begins in clouds as snow
If the air is colder than 0°C all the way to the ground, the precipitation falls as snow
SNOWSTORMS
In California, snowstorms generally occur only at high elevations
Californians depend on snow to provide part of their fresh water needsSnow that accumulates during the winter melts in the spring and summer
This snowmelt provides fresh water for a variety of needs, including irrigation and electricity production
SNOWSTORMS
A hurricane is a cyclone that has winds of 119 kilometers per hour or higher
Form in the Atlantic, Pacific, and Indian oceans
In the western Pacific Ocean, hurricanes are called typhoons
HURRICANES
A hurricane begins over warm ocean water as a low-pressure area, or tropical disturbance
HOW HURRICANES FORM
A hurricane draws its energy from the warm, humid air at the ocean’s surface
As the air rises from the clouds, more air is drawn into the system
The lower the air pressure at the center of the storm, the faster the winds blow toward the center
HOW HURRICANES FORM
Hurricane winds are strongest in the narrow band around the center of the storm
At the center is a ring of clouds, called the eyewall, that enclose the quiet “eye”
HOW HURRICANES FORM
Hurricanes last longer than other storms Usually a week or more During this time they can travel quite far
Hurricanes that form in the Atlantic are steered by the trade winds toward the Caribbean islands and the southeastern United States
After a hurricane passes over land, it no longer has warm, moist air to draw energy from, and gradually loses strength
HOW HURRICANES MOVE
What weather conditions are most likely to produce tornadoes?
Why do tornadoes occur most often in “tornado alley?”
CHECK FOR UNDERSTANDING
What weather conditions are most likely to produce tornadoes?Think cumulonimbus clouds along a front are the conditions most likely to produce tornadoes.
Why do tornadoes occur most often in “tornado alley?”The area known as “tornado alley” often has cold dry air meeting warm, moist air.
CHECK FOR UNDERSTANDING
What is a hurricane?A hurricane is a tropical cyclone with very high winds.
How do hurricanes form?Hurricanes form when low pressure systems form over warm water. The rising warm, moist air adds energy to the system, which eventually becomes a hurricane.
GUIDED PRACTICE