Posted by: pyeager | August 20, 2009

Forecast Accuracy

The publication Smart Money recently wrote an article about the 10 Things that Weather Forecasters Don’t Want You to Know, which is part of their Spending Rip-offs section. It’s an interesting read, so I thought that it would be interesting to look at these (at least some of them) from the perspective of someone who has worked in the field for decades.

Let’s look at one of their rip-off statements today:

“Long-term forecast? Your guess is as good as ours.”

There are two types of long-range forecasts–one several days out, such as days 6 through 10 of a 10-day forecast and a seasonal forecast. This statement is related to the former, and the article gave a few statistics about the relative inaccuracy of these forecasts, at least related to temperature.

The article makes a point about the limited value of these forecasts–they’re generally not very good. The majority of these forecasts are merely numbers generated from a computer forecast model, not the combination of computer guidance and human forecaster expertise, which is needed for a more precise forecast. In other words, it’s forecast automation.

Cost Reduction

Unfortunately, many forecasts are now automated in order to “increase efficiency” and “reduce costs.” A great percentage of forecasts seen today, including nearly all Internet forecasts, most newspaper forecasts, and even quite a few television forecasts, are automated–no meteorologist needed. The result is a forecast with frequent temperature change and often includes such phrases as “isolated thunderstorms” in each day of a 10-day forecast.

Not a Guess, but Close…

It has negatively affected accuracy, and while the forecasts are certainly better than you could do at home, I doubt that forecasting companies want you to know that their forecasters had no hand in the forecast.

–Paul Yeager


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