These charts give the weatherman a good overview of how the weather is currently. By viewing a series of charts, a pattern of weather is able to be shown. Based on the most recent shifts of highs and lows, the weatherman is able to mark out their probable position for tomorrow. This will give him a fairly accurate indication of what will happen weather-wise tomorrow. Yet, the weatherman cannot control the weather.
Many variables come into play.
A low pressure center may change speed or direction. A disturbance may weaken. Weather forecasting, however, is not guesswork. It is a highly developed skill some would say even an art. But, no matter how skilled he is, the meteorologist can never guarantee certain weather conditions.