Scientists usually forecast the weather using a(n) synoptic weather map. By using station models, this map shows a(n) summary of the weather. Scientists compare maps made every six hours to tell how weather systems are moving. With statistical forecasting, scientists find that patterns repeat. Another way to predict the weather is knowing how the atmosphere is moving. This requires millions of calculations by computers. These predictions are compared with forecasts to account for differences. Five-day forecasts are computed every day.