Isotherms Lines on a weather map that connect points where the temperature is the same. Orographic Lifting Lifting of air caused by its passage up and over mountains or other sloping terrain. Frontal Wedging Warm air and cold air collide, since warm air is less dense it is wedged upward and usually causes rain Cold Wave Extended period of lower than normal temperatures caused by large, high pressure systems of continental polar or arctic origin El Nino Warm ocean current that develops off the western coast of South America and can cause short term climate changes felt worldwide. La Nina A cooling of the surface water of the eastern and central Pacific Ocean, occurring every 4-12 years causing unusual weather patterns. The cooler water brings drought to western South America and heavy rains to Australia and Indonesia Coriolis Effect Deflects moving particles such as air to the right above the equator and to the left below the equator: caused by Earth's rotation and combines with the heat imbalances found on Earth to create the trade winds Cyclone A system of winds that spiral in toward a region of low atmospheric pressure, circling counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere Wind The horizontal movement of air relative to the earth's surface. Frontal Thunderstorms Type of thunderstorm usually produced by an advancing cold front, which can result in a line of thunderstorms or, more rarely, an advancing warm front, which can result in a relatively solid thunderstorm. Thunderstorm A storm with lightning and thunder. Its produced by a cumulonimbus cloud, usually producing gusty winds, heavy rain and sometimes hail. Tornado Appears as a violent funnel-shaped wind vortex in the lower atmosphere with upward spiraling winds of high speeds - spawned by severe thunderstorms. In area, it is one of the least extensive of all storms, but in violence, it is the world's most severe. Severe Thunderstorm A thunderstorm which produces tornadoes, large hail, or winds of 50 knots or more. Structural wind damage may imply the occurrence of a severe thunderstorm. Severe Weather Refers to any dangerous meteorological phenomena with the potential to cause damage, serious social disruption, or loss of human life. Station Model Is a symbolic illustration showing the weather occurring at a given reporting station. Meteorologists created the station model to fit a number of weather elements into a small space on weather maps. Fujita Tornado Intensity Scale Classifies tornado according to their wind speed, duration, and path of destruction on a scale of F0 to F5 Saffir-Simpson Hurricane Scale Classifies hurricanes according to air pressure in the center, wind speed, and property damage potential on a scale ranging from Category 1 to Category 5 Temperature Inversion condition in which the temperature of the atmosphere increases with altitude in contrast to the normal decrease with altitude. When temperature inversion occurs, cold air underlies warmer air at higher altitudes. Hurricane Also known as Typhoon, Tropical Cyclones, Willy- Willies. Tropical storms with wind speeds of 64 knots (117km/h) up to 240 knots (414 km/h) that can be thousands of square kilometers in size. Such systems usually have a lifespan of several days. Urban Heat Island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The main cause of the urban heat island effect is from the modification of land surfaces.