Forecasting the weather Weather: The state of the atmosphere at a specific time and plac e. Meteorologist: scientists who study the atmosphere Weather forecasts are issued: – to save lives – reduce property damage – reduce crop damage – to let the general public know what to expect

How far ahead can meteorologists accurately predict the weather? 0-12 hrs: pretty accurate except for unpredictable local storms hrs: are able to predict which areas will be hit by severe storms. 3-5 days: big events or storms can be predicted (hurricanes, floods) days: can give an average temp for a period of time.

How do they do it? Meteorologists look at: – Existing weather conditions over a large area. – Current data gathered from: Satellite images Weather stations Weather balloons – This data includes: Atmospheric pressure Wind direction and speed Temperature of the air Humidity, clouds, and precipitation Three important factors that shape the weather in a given region are: temperature pressure water Three important factors that shape the weather in a given region are: temperature pressure water

Making a weather map The basic tool of a weather forecaster is the WEATHER MAP. The weather map shows the: – distribution patterns of atmospheric pressure – wind – temperature and humidity at the different levels of the atmosphere.

Low and High Pressure Systems When a cold front moves into a region and warm air is forced upward, an area of low pressure is created near Earths surface. A center of high pressure tends to be found where a stable cold air mass has settled in a region. Remember: Wind is a horizontal movement of air from a area of high pressure to an area of low pressure.

Isobars Curved lines that indicate areas of equal air pressure. Indicate wind speed and wind direction Closely spaced lines= high change in pressure + high wind speed. Widely spaced lines= slow change in pressure + low wind speed. High pressure system (depicted by an "H") Low pressure system (depicted by an "L Iso = equal bar = pressure

Wind Winds are identified as the direction FROM which they come. From which direction is the wind coming according to this wind feather? From which direction is the wind coming according to this wind feather?

Weather Symbols fog haze thunderstorm, drizzle lightning rain * snow slight rain showers. ice or snow pellets cloud development not observed

no clouds about 10% about 25% about 40% about 50% about 60% about 75% about 80% completely overcast sky obscured