The magic behind the Old Farmers Almanac weather forecast

Their forecasting technique comes from a 'secret formula' - but it's easily open to criticism.

The Old Farmers Almanac is one of the most revered and beloved publications in the U.S. That might explain why it's been in circulation since 1792 - when George Washington was our president.

The magazine puts out a long-term weather forecast that may be their most popular section.

Likely, because it comes out 18 months in advance. Earlier than any other climate forecast. The National Oceanic and Atmospheric Administration has a winter outlook that they usually release in October.

So obviously the NOAA forecast will be more accurate because it comes out just 2 months in advance. 

However, there is some mystery involved in the Old Farmers Almanac that leaves them open to criticism. 

They say their forecasts come from a secret formula devised by the Almanacs founder, Robert Thomas back in 1792, who believed that weather is influenced by sunspots. They say they have refined their formula over the years.

They claim to be 80 accurate, but that is a self-proclaimed record. There is no way to really check their math, because they don't publicize how they compute their numbers, nor do they say what data they use to compare their results.

Thus the magic of the Old Farmers Almanac may be in its presentation, using a clever arrangement of averaging and vagueness.

They break their forecasts down into 18 zones.

Denver is part of the High Plains Zone. Which gets the same forecast as places like Billings, Montana, Rapid City, South Dakota, and even Amarillo, Texas.

So lets look at some numbers.

.......................................NOV | DEC | JAN | FEB | MAR |                                  
Old Farmers Almanac |     2    |   -3   |    0   |   5    |    5    |
Actual Denver Temp   |    6.8   | -2.2  | -0.7 |  7.7  |   7.5  |
Difference                   |    4.8   |  0.8  |  0.7 |  2.7   |  2.5   |  

The graph shows the Old Farmers Almanac forecast for the High Plains zone from last November to March of 2017, in degrees above or below normal, and the actual observed temperature for Denver, in that time period.

Not bad, but nowhere near 80 percent accurate if you use just Denver as the gauge.

They do publish their own report card every year, but they only list one city in that zone on their report, and they don’t say where they get their numbers.

For last winter, they list Rapid City in their report for the High Plains Zone, and say they predicted a .1 degree variance, and they show the actual temperature during that time was .3 degrees above normal.

But a check of the National Weather Service’s monthly temperature summary for the Rapid City station during that same time period shows it was actually 1.4 degrees above normal.

So that leaves the question, where did the Almanac get their temperature data?

They do not say, but they may average the whole High Plains region, which spans more than 1,000 miles of advantageous and varying latitude.

So they don't tell you how they make their forecast, and they don't tell you what data they use to grade themselves.

You could say it’s a bit of hocus pocus, or just a brilliant arrangement of averages. Either way I doubt the Old Farmers Almanac will ever loose is huge popularity.

© 2017 KUSA-TV


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