Richardson's ideas were shelved as being theoretically interesting but impossible in practice. After the second World War, computers developed, initially, for code breaking and artillery calculations were seized upon as the means by which Richardson's ideas might be realised. Since then meteorologists have been specifying needs for bigger and faster computers while improving the calculation of all the various processes that occur in the atmosphere. Perhaps, it should be emphasised here that statistical techniques are not used. The computers do not use past experience, they start with the current state of the atmosphere and calculate how the atmosphere will evolve.
Forecast errors occur for three main reasons.
First, even with many land observing stations, many ships, buoys and aircraft providing data over the oceans and with satellites continuously providing information from space, there are still uncertainties in knowing sufficiently accurately the present conditions. Improvements are taking place but the problems are great and very costly to solve. Secondly, even the biggest computers available cannot handle all the physical processes sufficiently accurately and, probably, never will. What is happening is that the very necessary approximations are continually being refined and improved. The aim has to be to produce the best forecast possible although this may be far from the best possible forecast.