Weather is dependent on a number of factors like humidity, atmospheric pressure, ambient temperatures, rains, wind speed and direction and more. Different instruments are used to measure each of these parameters. The meteorological department of each country collects this information to forecast the weather.
Anemometer is used to measure the direction of the wind, hygrometer is used to measure the humidity in the air, rainfall is measured by the rain gauge, and the sunshine recorder measures the duration of the sunshine. Since various factors collectively determine the weather, each of it is separately measured and then combined at the meteorological office to forecast the weather of a particular place. Barometers are used to get the measure of the atmospheric pressure. The atmospheric pressure and the direction and speed of the wind are calculated to determine storms and hurricanes. Satellites are also being used to determine weather with more accuracy.
Nowcasting is referred to as the weather forecasting in the immediate next six hours. In the small time range, it is easier to forecast smaller features of the weather such as showers and thunderstorms with more accuracy. Weather forecast for immediate period is more accurate than for larger time gaps.
In recent times, human input to forecast weather is restricted only to selecting a model to fore cast weather. The rest of it is done by instruments and computers. The data is fed to the computer of the various weather parameters and the weather is forecast is generated by the machine. Humans use the model results and interpret them into weather forecasts for the common man to understand. Humans are also helpful to forecast weather with small inputs which are not useful for machines. With small inputs professionals can forecast the weather.
The simplest method to forecast weather is persistence. This method basically relies on today’s weather to forecast tomorrow’s weather. This method is quite accurate when the weather conditions are stable. It is useful for both short and long range forecasts.