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New Weather Computer
Sarah writes "It seems that the National Weather Service has a brand-new computer which will allow them to predict the weather earlier and more accurately. If I were a kid, I could now plan my snow days in advance..." Yeah, but the teachers would give you enough homework to last you through the day.
One word: butterflies.
Acfoo dun said:
Short Answer: because weather is chaotic.
Long Answer That Probably Tells You More Than You Wanted To Know :) :
Weather systems were, oddly enough, the first systems proven to have sensitive dependence on initial conditions (the defining characteristic of a nonlinear system). A person by the name of Lorenz discovered this in early attempts to model weather systems in the late 50's/early 60's, and more and more complicated weather simulation systems have proven it even more. (As a minor aside: Both the strange attractor associated with Lorenz's discovery and the effect of it in RL are known as the "Butterfly Effect"; the attractor looks much like a butterfly, and sensitive dependence on initial conditions may be summed up roughly as "A butterfly flapping its wings in Brazil may cause enough perturbation in the atmosphere to cause a tornado in Texas a few days down the line". That's also why the one fella in this thread keeps mentioning butterflies, btw. :)
As it turns out, a large number of the variables in weather forecasting are nonlinear. Not only that, in many areas you have multiple weather influences that can brew up storms in a jiffy and make them dissipate almost as quickly (the Ohio Valley--which lies on an eastern extension of Tornado Alley--is infamous for this: cold air rushes towards us from Canada, warm air from the Gulf which is nice and moist, the jet stream frequently puts enough twist in the air, and we usually catch stuff from the "big" Tornado Alley out west...all this together means storms can brew up with amazing speed and fury out here ["popcorn" tornadic thunderstorms aren't unknown here--we had some pop up January 3-4th, which proceeded to spawn an F3 tornado which hoovered a fair portion of the city of Owensboro, and the 1995 tornado that hit the Mt. Washington area [south of Louisville] brewed up about that quick--not the tornado, the supercell that spawned it...); also, fun statistic: Kentucky is not in the top ten for tornados per state, but IS in the top ten for killer tornados per state and killer tornados per square mile--in other words, we don't get them as often as Oklahoma, but when we get them they tend to be F2-F3 and up)...to the point we joke that Ohio Valley weather is more chaotic than chaos itself :)
To be honest, I'd say fourteen days is DAMNED optimistic. I have never seen a forecast in my area that was more than three or four days old that was anything close to being accurate (of course, I live in the Ohio Valley, which has weather systems that make chaosologists cream, meterologists scream, and put the fear of God into storm chasers to the point they state they think the Ohio Valley is entirely too dangerous to chase tornados in :)...usually in Knoxville, TN I've found the forecasts more accurate because they don't have to deal with as much crap variable-wise). Even in relatively calm areas five or six days is REALLY stretching it...I honestly don't think meterology is going to be able to improve much on that. You might get more detail (a better idea of where snow will fall and maybe how much), but you aren't going to get any closer to longterm forecasts, and in the spring in the Ohio Valley you'll be lucky sometimes to get one or two days in during storm season. (Hell, I'll be impressed if they can actually determine accurate amounts of snowfall. I have NEVER, EVER in my 26 years seen an accurate snowfall amount forecast; hell, 50% of the time they can't even tell if it's going to be snow, freezing rain, or sleet...and this is with folks in the NWSFO who have been there longer than I've been alive, and with the most experienced TV meterologist having done weather here for some thirty years (to the point he helps out the NWSFO at times) and who also teaches the advanced meterology classes at U of L...and all of them completely and utterly unable to tell how much snow one will get. All of them missed the 1994 super-snowstorm (24 inches in one snowstorm in Louisville, which is a record--the city, for which four or five inches starts to be a "big snow", was literally paralysed for a month and the only way one could get anywhere was by 4WD...the city and county governments were literally commissioning folks with high-clearance 4WD vehicles to transport folks to the hospitals and suchlike)... like I said, I'll be IMPRESSED if they can get to the level of predicting how much snow will fall, much less long-term forecasting. :)
And as for experience with weather modeling...most of mine is in using them for my own attempts at forecasting (I'm just a wee bit of a weather nut, to the point I'm seriously considering taking Skywarn classes and maybe even meterology courses in future, though I'm NOT up to chasing tornados just yet :). If you've been in an area for some time you learn which models work best (there are actually several different models, such as the NGM, the AVN, the ETA, etc.) for the way the weather actually behaves in your area...the most important computer in any forecast is the big meaty two-pound one between yer ears :)
-Windigo The Feral (NYAR!)