In addition, satellite instruments peer down from space and measure temperature, cloud cover, and wind. Every 12 hours, a global network of balloon soundings, or readings, are taken to measure the pressure, temperature, winds, and humidity in the upper atmosphere. From this data, forecasters draw maps showing the current areas of high and low pressure, where clouds and precipitation are occurring, how the jet stream is moving, and the location of cold fronts and warm fronts. Meteorologists make a temperature forecast by using a map of current winds and temperatures at the earth's surface. If the surface wind is blowing from an area where it is warmer, we can expect warmer air to move into the region.
Northerly winds tend to bring in colder than normal temperatures.
A good way to make a precipitation forecast is to study an animation of the precipitation from weather radar over time. By studying the motion of the precipitation, one can estimate the direction and speed it is moving at, and make a forecast of when it will arrive in a certain place. This technique has some limitations though, because storms can weaken or intensify, or change course. That is why what meteorologists do is called forecasting. It is our best guess, and sometimes it is wrong.