While a huge amount of computer processing power is spent predicting the weather, a fair part of that could be going to waste because of software faults.
A study by Korean researchers has found that the flaws in software mean that you might as well predict the weather using tarot cards.
The researchers wanted to look at the simulation results from a global atmospheric numerical model on machines with different hardware and software systems.
Song-You Hong, of the Department of Atmospheric Sciences, College of Sciences, Yonsei University, Seoul tested the commonly used global model program and the Global/Regional Integrated Model system on 10 different computer systems with different CPU's, architectures or compilers.
It was found that each bit of hardware, using the same software, gave a different prediction.
The paper deals with 10-day weather forecasts when weather forecasts are generally done in one hour steps. It assumes that the data from the first hour tended to be right, and was calculated correctly.
It speculates that the reason for the problem is because some parts of the software are rounding up or down incorrectly. Other suggestions are that there are approximations in built-in functions.
This problem becomes more marked over time so that on the tenth day the result is so realistic that it is predicting that Daenerys Targaryen will be invading the North-west of England with an army of dragons on Tuesday with thundery squalls of badgers off the Orkney and Shetland Islands by Wednesday.