Chapter 3:Weather Patterns
Storms Quiz: Section 2
Study Guide
Vocabulary:
Storms: a violent disturbance in the atmosphere
Thunderstorm- heavy rainstorms accompanied by thunder and lightning
Lightning: a sudden spark, or energy discharge, caused when positive and negative charges build up and move
between parts of a cloud.
Thunder: sound of the explosion causes by rapidly heated air expanding
Tornado- a rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud and touches the ground
Tornado Watch- an announcement that a tornado is possible
Tornado Warning- an announcement that a tornado has been spotted
Tornado Alley- location in the mid-west where most tornadoes occur
Fujita Scale- measures a tornado based on intensity (wind speed and damage) From F0-F5
Water Spout: Tornado occurring over a lake or ocean
Hurricane- a huge tropical storm with wind speeds of 74 mph (119 kph) or higher
Eye- the calm and clear center of a hurricane
Storm surge- a dome or wall of water that sweeps across the coast where a hurricane lands
Thunderstorms:
 How Thunderstorms form?
o Warm, humid air is forced upward at a cold front
o Warm humid air rises rapidly and cools
o Forms large cumulonimbus clouds or thunderheads
o Rain/hail/heavy wind (produce strong upward and downward winds- updrafts and downdrafts
 Lightning can be as hot as 30,000 degrees Celsius
 Lightning moves from one part of a cloud to another, between clouds and from clouds to the ground
 You see lightning before you hear thunder because light travels faster than sound
 Thunderstorms occur all over the world
 Does not always happen at a cold front- can occur when large amounts of moist air rises quickly
 Usually occur in spring and summer months, but can occur any time of year
 The Prevailing Westerlies move air masses from west to east, they can pull cold air down form the poles or
warm air up from the tropics
 Thunderstorm Safety
o Avoid touching metal objects, telephones, or electrical appliances
o Stay out of open areas
Tornadoes:
 How and when do they occur?
o When warm, humid air masses (maritime Tropical from the Gulf of Mexico) meet cold, dry air masses
(continental polar from Canada) Cold air moves under warm air, which rises quickly
o As warm air rushes past cold air, creates a vortex, with high winds
o Spring and summer- ¾ of all tornadoes occur in the US between March and July
 Brief but deadly- strong winds, flying debris
 Wind speeds may approach 480km/hr
 Can cause hail
 Tornado Alley- Great Plain States- runs from north-central Texas across central Oklahoma, Kansas and
Nebraska
 Tornado Safety
o Move to a safe area- basement of a well built building
o Stay away from windows and doors
o Lie on the floor under a sturdy piece of furniture
o Outside? Move to a ditch or building
Hurricanes:





Hurricane: tropical storm with winds 74 miles per hour or higher, approximately 600km across
Hurricanes in the Western Pacific Ocean are called typhoons, in Australia they are called cyclones
In US, most occur in later summer and early fall, from August to October
Destructive
Bring large amounts of rain
 How Hurricanes Form:
o hurricanes begin over warm water as a low-pressure area, or tropical disturbance
o tropical disturbance
tropical storm
hurricane
o lasts a week or more
o gets its energy from the warm, humid air at the ocean’s surface
o Rotates in a counter clockwise direction in the northern hemisphere
o wind spirals inward into the areas of low pressure
o bands of heavy wind and heavy rain
o lowest air pressure and warmest temperatures are at the center of the hurricane (eye)
o the lower the air pressure at the center, the faster the winds blow
o winds can be up to 320km per hour
o In the US, most hurricanes follow a similar path: Northwest from the Trade Winds
Northeast from
the Prevailing Westerlies
 Eye of a Hurricane:
o center of hurricane is made of a ring of clouds surrounding the “eye”
o the wind gets stronger as the eye approaches
o when in the eye weather changes suddenly
o weather in the eye is calm and skies are clear
o after the eye passes the storm continues BUT the wind is blowing in the opposite direction
 Hurricane Damage
o High waves
o Severe flooding
o Wind damage
o Storm surge
o Destruction of buildings, coastlines
 Hurricane Safety
o Be aware of warnings/evacuations
o Hurricane warning: hurricane conditions are expected in your area within the next 24 hours- evacuate
immediately if told
Winter Storms:
 Snow falls when humid air cools below freezing
 High winds and dangerous temperatures
 Blowing snow, low visibility
 Lake Effect Snow:
o In the fall and winter the land near the Great Lakes cools faster than the water in the lakes
o Cool, dry air masses pick up water vapor and heat from the warmer lakes
o When the air mass reaches the other side of the lake, the air rises and cools again- forming clouds and
causing snow around the lakes to fall
 Snowstorm Safety
o Find shelter from the wind
o Cover exposed parts of the body and stay dry
o In a car? Keep the engine running and clear snow away from exhaust