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Air Masses, Fronts, and Severe Weather Earth Science Grade 8 Air Masses An air mass is a body of air that has the same properties as the area over which it developed. Air Masses There are four categories that determine an air mass’s characteristics: developed over land: continental = c developed over water: maritime = m developed over cold area: polar = P developed over warm area: tropical = T Air Masses Air masses that could develop: (Combine the two possibilities) 1. cT 2. mT 3. cP 4. mP Fronts Fronts are where two air masses meet. Their names are determined by the moving air mass. Precipitation occurs along all fronts Four Types of Fronts COLD FRONT When cold air moves into an area of warmer air Weather caused: Thunderstorms and heavy rain It’s symbol on a weather map looks like this: Four Types of Fronts WARM FRONT When warm air moves into an area of colder air Weather caused: long, steady rains It’s symbol on a weather map looks like this: Four Types of Fronts OCCLUDED FRONT When colder air moves into an warmer area of air at an angle. The masses start to spin! Weather caused: severe weather like tornados It’s symbol on a weather map looks like this: Four Types of Fronts STATIONARY FRONT When two air masses do not move!!! Weather caused: same weather for days (all nice or all bad) It’s symbol on a weather map looks like this: Severe Weather Thunderstorms Thunderstorms result from the rapid upward movement of moist air. As this air moves upward it cools, condenses, and forms cumulonimbus clouds Cumulonimbus Clouds Cumulonimbus Cloud with Lightning Lightning Lightning is a large release of energy during a thunderstorm Thunder is the rapid heating of the air surrounding the lightning bolt…fast enough to break the sound barrier! http://www.youtube.com/watch?v=h7c6z_3dLE4&feature=related Hail In thunderstorms the updrafts can be so severe that the rain coming down can be thrown back up into the cloud. This causes the rain to freeze in layers creating hail. Hail formation Tornadoes When thunderstorms reach extremely low pressures, they can create tornadoes. Tornadoes are violent whirling winds that move in small areas over land. Even though the are relatively small storms, and last for only a few minutes, they are one of the MOST DESTRUCTIVE storm on land. Tornadoes Water Spouts Tornado Sisters Fujita Scale Measures the destruction of the Tornadoes Most Famous Tornado http://www.youtube.com/watch?v=MhPu5AHDMHM Hurricanes The largest and most powerful storm on the planet is the Hurricane. It is a large, swirling, low pressure system that forms over tropical oceans along the equator. Hurricane Formation A storm develops over the ocean is first called a tropical depression. Wind speed up to 38 mph Once the winds reach 39 mph the depression becomes a tropical storm and gets a name. Once the winds reach 74 mph the storm becomes a hurricane. A hurricane will continue to grow as long as it is over warm, tropical waters. Hurricane Names Hurricanes are named alphabetically switch from boy to girl (or girl to boy). 2010 2011 2012 2013 2014 2015 Alex Bonnie Colin Danielle Earl Fiona Gaston Hermine Igor Julia Karl Lisa Matthew Nicole Otto Paula Richard Shary Tomas Virginie Walter Arlene Bret Cindy Don Emily Franklin Gert Harvey Irene Jose Katia Lee Maria Nate Ophelia Philippe Rina Sean Tammy Vince Whitney Alberto Beryl Chris Debby Ernesto Florence Gordon Helene Isaac Joyce Kirk Leslie Michael Nadine Oscar Patty Rafael Sandy Tony Valerie William Andrea Barry Chantal Dorian Erin Fernand Gabrielle Humberto Ingrid Jerry Karen Lorenzo Melissa Nestor Olga Pablo Rebekah Sebastien Tanya Van Wendy Arthur Bertha Cristobal Dolly Edouard Fay Gonzalo Hanna Isaias Ana Josephine Kyle Laura Marco Nana Omar Paulette Rene Sally Teddy Vicky Wilfred Hurricane Names 2010-2015 Bill Claudette Danny Erika Fred Grace Henri Ida Joaquin Kate Larry Mindy Nicholas Odette Peter Rose Sam Teresa Victor Wanda Eye and Eye Wall of the Hurricane The eye of the storm is the calm area in the center of the storm. The eye wall is the bank of clouds immediately next to the eye…this is the most severe part of the storm.