The Perils of Predicting Weather

Weather Vane


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Here at The Old Farmer’s Almanac, we have often explained the forecasting methodology that we use to predict the weather.

Traditionally, our methodology has been based upon the precept that the Sun controls Earth’s weather and that the patterns of solar cycles as a predictive tool enable us to forecast Earth’s weather a year or more in advance. Once we determine what the solar activity is likely to be, we find analog years during which solar cycles were similar and thus forecast the weather to be comparable.

However, two factors have put added pressure on our forecasts in recent years: 

  • The last time activity in the solar cycle was this low, we did not yet have widespread reliable weather records (analogs), so we are forced to extrapolate and speculate on past weather activity; and 
  • With the climate changing, the effects that the Sun has on Earth’s weather patterns seem also to be changing from what they may have been in the past. Thus we need to break new ground in determining what this means for future weather.

See a more complete explanation of these maps.

Our core methodology essentially tells us what weather to expect, and we use that to determine the Earthly patterns that ultimately lead to our weather forecast. 

For example, our methodology told us that California would have below-normal precipitation; from this, we inferred that since strong El Niños almost always bring above-normal rainfall to California, there would not be a strong El Niño this winter. (To be clear, our methodology did not tell us directly “there will not be a strong El Niño.”) Clearly, we were wrong, as this winter brought the strongest El Niño on record. 


What Happened?

According to NOAA (the U.S. National Oceanic and Atmospheric Administration, the parent organization of the U.S. National Weather Service), the jet stream in the Pacific set up farther north than usually happens during El Niño winters due to various other factors. 

As a result, we may turn out to be correct in our precipitation forecast for California despite the strong El Niño. California precipitation (at least as I write this in late February 2016) has been below normal for the season thus far. However, our temperature forecasts were too cold, as the nation as a whole was considerably warmer than we forecast—warmth being another characteristic of an El Niño. 

One of the most severe examples of this may be Fairbanks, Alaska. We forecast that Fairbanks would average 8 degrees F colder than normal this past winter season—this was after having made an adjustment for climate change (one of the largest adjustments we have ever made, by the way): We raised our forecast by 7.5 degrees. As it turned out, we should have raised that forecast by about 20 degrees! Fairbanks had an extremely mild winter.


Current forecasts of ENSO (the “El Niño Southern Oscillation”) have the strong El Niño weakening in the spring and transitioning to a La Niña by fall, which should mean very different weather next winter. Next month, we’ll give you a hint of what to expect. In the meantime, enjoy spring conditions!

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