Types of Severe Weather • Thunderstorms – Lightening – Thunder • Tornadoes • Hurricanes Thunderstorms • Lightning is an electric discharge that occurs between a posively charged area and a negavely charged area. Thunderstorms are very acve electrically. • Thunder is the sound that results from the rapid expansion of air along the lightning strike. Tornadoes • A tornado is a small, spinning column of air that has high wind speeds and low central pressure and that touches the ground. • A tornado starts out as a funnel cloud that pokes through the boom of a cumulonimbus cloud and hangs in the air. The funnel cloud becomes a tornado when it makes contact with Earth’s surface. Hurricanes • How a Hurricane Forms A hurricane begins as a group of thunderstorms moving over tropical ocean waters. Winds traveling in two different direcons meet and cause the storm to spin. • Damage Caused by Hurricanes Hurricanes can cause a lot of damage when they move near or on to land. Wind speeds of most hurricanes range from 120 to 150 km/h. Hurricanes El Nino • El Nino‐ a warm‐water event occurs in the tropical Pacific Ocean where winds shi & push warm surface water toward the west coast of South America • Occurs once every 2 to 7 years & cause dramac climate changes around the Pacific Ocean & nearby areas such as droughts, floods, & tornadoes • The only semi‐reliable way to predict an El Nino is to noce the rising surface temperatures of the tropical parts of the Pacific Ocean Weather Forecasng • Meteorologist‐ sciensts who study the causes of weather & try to predict it • Meteorologists use informaon from many sources including local weather observers, weather balloons, satellites, & weather staons around the world Radio-sonde Satellites Weather stations Radar Weather ship Supercomputer and weather buoys Aviation Forecaster National and International Shipping Global forecast services Forecast Services up to Weather forecasting 7 days ahead. Weather Forecasng • Staon Models are shared from hundreds of locaons and fed to the Naonal Weather Service • The symbols are used to describe a weather condion Weather Forecasng Weather Accuracy • Short‐range forecasts (12 to 72 hours) are quite accurate • Medium‐range forecasts (3 to 7 days) are now fairly reliable, and have shown significant improvement over the last 20 years as technology has improved. • Meteorologists also make long‐range predicons, which aren’t as accurate but were once impossible to do Weather Tools • Meteorologists use several tools to help them predict the weather including: – Weather Balloons – Satellites – Computers to interpret/calculate data – Weather Maps (from other staons, Naonal Weather Service, etc.) Weather Balloons & Satellites • Weather Balloons carry instruments high into the different layers of the atmosphere to collect weather data such as temperature, air pressure, & humidity • The first weather satellite was launched in 1960 • Cameras on weather satellites can photograph Earth’s surface, clouds, storms, & ice & snow cover Computer Forecasts • Can be used to gather & interpret thousands of bits of data about temperature, air pressure, wind speed, & other factors quickly • The computer starts with weather condions reported over a large area, then it works through many calculaons to make a 12 hour , 24 hour, & 36 hour forecast • As new informaon comes in, the forecast is adjusted Reading Weather Maps • A weather map is a “snapshot” of weather condions at a parcular me in a parcular place • There are many different types of weather maps such as computer or radar maps Weather Service Maps • Data from more than 300 local weather staons are complied at the Naonal Weather Service to help produce a map • The curved lines on weather maps connect places where certain weather condions‐ temperature or air pressure‐ are the same Isobars & Isotherms • Isobar‐ lines joining places on the map that have the same air pressure – iso means “equal” & bar means “pressure” – the numbers on the isobars readings are measured in either inches of mercury or in millibars or both Isobars • Isotherms‐ lines joining places that have the same temperature – Iso means “equal” & therm means “heat” – will be labeled with the temperature in Fahrenheit, degrees Celsius, or both Isotherms Newspaper Weather Maps • These are simplified maps produced by the National Weather Service for public use • Standard symbols on weather maps show fronts, areas of high & low pressure, types of precipitation, & temperature (given in Fahrenheit degrees) .