"My phrenologist said your skull was trustworthy!"
It comes down to the same reasons predictions about the stock market, elections, and your dating life can all go horribly awry -- no matter how much past data and current trends you have access to, the future is uncertain. And the further into the future you look, the more uncertainty can play into it. "This is why we give more and more percentages now. We look at what's building, where the wind is going, and lots of other little factors," David says. "I use everything from real-time Doppler radar to a barometer installed here in the 1930s."
And the biggest state-of-the-art weather-viewing portal money can buy.
Meteorology has improved a lot over the past few decades. Five-day forecasts are about as accurate as two-day forecasts were in the '80s, and long-range predictions are improving too. Hurricane Sandy's American landfall was predicted more than seven days in advance in 2012, which would have been witchcraft in the '70s. But the weather is still a product of Mother Nature, and that bitch doesn't really give a damn about our "science."
"Even overnight expected inches of snow or temperature or wind speeds can change," he says. "There is that joke in Groundhog Day about Bill Murray getting the weather wrong the next day. That happens more times than I would like to admit. And they never showed someone writing in the salt on my car 'Good prediction asshole.'"
"And don't bother telling the cops. We're the ones that did it."
Meteorologists determine 10-day forecasts by evaluating historical data, pressure systems, cloud patterns, wind, what Old Man Jones is feeling in his bones, and much more. And even with all that data, six- to 10-day forecasts are 40 percent accurate, or only about 7 percent better than wild mass guessing. It's getting better, but for now, just plan your Saturday barbecues on Thursday instead of Monday.