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Gold/Mining/Energy : Gold and Silver Juniors, Mid-tiers and Producers
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To: E. Charters who wrote (14855)6/30/2006 2:59:38 PM
From: yard_man  Read Replies (1) of 78419
 
Lorenz was not working with the weather. He was working with a forecasting "system" -- a set of equations. These equations are a deterministic approximation of a real situation. That's what we are talking about with respect to forecasting. It matters not whether the weather itself is or is not chaotic -- it is the mathematical description we are concerned with.

Deterministic equations exhibit chaos -- play with the example given in all the textbooks:

x[n+1] = A*x[n](1-x[n]) --

let A = 4 and take two different x[n]s from [0,1] (not zero or the other fixed pt) -- compute 30 or 40 orbits and see how close they track ... no random variables involved at all. A precise rule and you still can't predict how the differences in the orbits will behave after so many iterations.

That summarizes the problem. Whether or not the weather is deterministic at the root -- no one knows -- any more than physicists know whether things are deterministic at the root or not. At some point it just becomes a philsophical argument.

The reason I got interested in the discussion was your implication that finer grids and more computing power could win the day. It can't. There are computational limits to forecasting -- no matter how fine the grid and how many digits you carry.

Why do you think people use scenarios?? Folks are interested in chaos for a reason -- there are patterns that repeat -- there are cycles -- pattern recognition and stable orbits are not the same thing as "stepping the clock and following all the parts."
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