These are the major types of severe weather that we will learn about today • Thunderstorms • Tornadoes • Hurricanes
A storm is a violent disturbance in the atmosphere. They involve sudden changes in air pressure, which cause rapid air movements
Thunderstorms Thunderstorms are heavy rain storms accompanied by thunder and lightning. Thunderstorms form within large cumulonimbus clouds, or thunderheads Watches- when conditions are favorable to produce a thunderstorm Warnings- Issued when a thunderstorm has already formed and is happening Warm Air Cold Front Most form when warm air is forced upward at a cold front. They can also form on hot, humid afternoons in the spring and summer. In both cases, this is when warm, humid air rises rapidly.
Lightning Areas of positive and negative electrical charges build up in the storm clouds during thunderstorms Lightning is a sudden spark, or energy discharge, as these charges jump between the parts of a cloud, between nearby clouds, or between the cloud and ground
Boom! What causes thunder?? Lightning can heat the air around it as high as 30,000C which is hotter than the surface of the Sun!! This heated air expands rapidly, suddenly, and explosively. Thunder is the sound of that explosion. Why do I see lightning before I hear it? Because light travels faster than sound, you will see lightning first! Think about a baseball game, you see the player hit the ball before you hear the crack of the bat.
Thunderstorm Safety Tips • Avoid metal objects • Stay out of water • Avoid electrical appliances, bathtubs or showers, and landlines, which can all conduct electricity
Tornadoes A tornado is a rapidly whirling, funnel-shaped cloud that reaches down from a storm and touches Earth’s surface Tornadoes develop in low, heavy cumulonimbus clouds Tornadoes occur more often in the United States than any other country. About 800 tornadoes occur in the US every year
Tornado Alley The Great Plains often have the type of weather patterns necessary for tornadoes Cold, dry air mass moves south from Canada and meets warn, humid air from the Gulf of Mexico A squall line of thunderstorms can develop and can produce ten tornadoes or more Tornado Alley includes north-central Texas, central Oklahoma, Kansas, and Nebraska, but any state could have a tornado Would you live there??
Tornado Safety Tornado watch means that conditions exist that could produce a tornado This means that you should pay attention to weather reports in case the weather should worsen or produce an actual tornado Tornado Warning means that a tornado has been spotted on radar on in person, and you should take cover in a safe place During a tornado, a “safe place” would be the most interior room in a house on the lowest level, away from windows and doors.
Tornado • Tornadoes are measured based on their wind speed/damage. • The Fujita scale is used to measure the intensity of a tornado by examining the damage caused by a tornado after it as passed over an area
Hurricanes Hurricanes begin as a low pressure area, or tropical disturbance , over warm water Hurricanes get their energy from the warm, humid air at the ocean’s surface. This air rises and forms clouds, drawing more air into the system Winds spiral inward toward the low pressure inside Inside the storm are bands of high winds and heavy rains The lowest pressure and warmest air is at the center of the hurricane in the eye
The Eye of the Storm The “Eye” of the hurricane is the center, “quiet” area. If you were to be in the path of this hurricane, you would notice that the winds get stronger and rain heavier as the eye approaches. In the eye, there would be calm winds and maybe even a clear sky. Then the eye would pass and the storm would resume, with the wind blowing in the opposite direction
Storm Surge One of the most dangerous features of a hurricane is the storm surge. Low pressure and high winds of a hurricane can raise the water up as much as 6 meters above normal sea level The result is a storm surge, or dome of water that sweeps on shore
How bad is bad? Hurricanes are measured based on the strength of their winds They start as tropical depressions, then advance to tropical storms, then advance to hurricanes Once winds are at least 74 mph, they are a Category 1 hurricane