Long Range Forcasting


Weather prediction. There are times when all of us just feel like screaming at our local forcaster. "Why can't the ever get it right?" we think. If we are lucky they can tell us weather of three, or maybe four days ahead. Sometimes they're right. But what about a week ahead, or a month? Naturally, chaos scientists had a go at this problem. Their conclusions however, are not going to be much more use if you want to choose a fine day for your birthday party in three months! There are many variables associated with the weather: temperature, air pressure, wind speed, wind direction, humidity and many more. The equations which control the weather involve all of these variables. You can accurately put all these variables in an equation and calculate, with some degree of certainty the value of all the variables one second hence. These answers can be fed back in, and the values for the next second can be calculated one second hence. These answers can be fed back in, and the values for the next second can be calculated. Leave the poor computer go for long enough to do the iterations and you will know the weather one month later. Or will you? Edward Lorenz worked with this hypothesis. Lorenz decided to run a computer the program to test just that. To do so he entered the values for the weather prediction halfway through the run and set the machine off again. But, the results soon deviated from the previous run. Lorenz found the reason was that he had put the values in accurate to three decimal places. The computer had calculated to six places. So a difference of one in a thousand was enough to change the output significantly. Science can't measure the variables accurately enough to avoid the effects of chaos. For ten years, Lorenz's paper on this result was ignored, despite Lorenz being aware that this was a crucial discovery. When he plotted the three key variables in three dimensional space, he gained a plot that came to be known as the Lorenz Attractor. To download a picture of the Lorenz Attractor, please go to our download section.