Transcript Weather
Weather Fronts Target #15- I can describe a weather front • When two unlike air masses meet, density difference usually keep the air masses separate. – Cool air masses are denser than warm air masses – Their interaction is called a front • Can be several hundred to several thousand kilometers long • Initiates weather activity • For a front to form one air mass must collide with another air mass –Kind of front determined by how the masses move in relationship to each other Target #16- I can state how a front forms Target #17- I can differentiate between the types of weather fronts that can form • Cold Front: occurs when a cold air mass overtakes a warm air mass – The cold air lifts the warm air mass • If the warm air is moist, clouds will form – The faster the front moves the stronger the storms • Squall line: where thunderstorms form along a fast moving cold front • Warm Front: occurs when a warm air mass overtakes a cold air mass – Less dense warm air rises over the cooler air – Generally produces precipitation over a large area – May cause violent weather • Stationary Front: occurs when two air masses meet, but neither displaces the other – Either moves slowly or not at all – Weather produced is similar to a warm front • Occluded Front: occurs when a fastmoving cold front overtakes a warm front and lifts the warm air off the ground completely – Usually results in rain storms • Mid-latitude cyclones – A wave forms at the boundary where cold polar air meets tropical air • Usually occurs in the mid-latutides (half way between the equator and the poles) – Hurricanes: Over oceans – Tornadoes: Over land • Illustrated by a counter-clockwise rotation of air Target #18- I can describe a midlatitude cyclone Target #19- I can state how a mid-latitude cyclone forms Target #20- I can describe hurricanes • Hurricane – a tropical storm that forms over a warm ocean – has strong wind speeds of more than 120 km/h • spirals toward its intense low pressure center – Begins when warm, moist air over the ocean rises rapidly • Winds increase toward the center (the eye) – Causes a storm surge rising sea level Target #21- I can summarize the impact a hurricane induced storm surge has on the environment • Storm surges are frequently the most devastating element of a hurricane. – As a hurricane’s winds spiral around and around the storm, they push water into a mound at the storm’s center. • This mound of water becomes dangerous when the storm reaches land because it causes flooding along the coast. • The water piles up, unable to escape anywhere but on land as the storm carries it landward. – A hurricane will cause more storm surge in areas where the ocean floor slopes gradually. This causes major flooding. • Safir-Simpson Scale: a 5 category scale that groups hurricanes into groups by pressure, wind speed, and storm surge Target #22- I can identify what scale is used to measure the strength of a hurricane Target #23- I can describe tornados • Tornado: a destructive rotating column of air that has very high wind speeds and that is visible as a funnelshaped cloud – Forms when a thunderstorm meets high-altitude winds – The winds cause the rising air to rotate – Moves unpredictably – Measured by the Fujita Scale Twister