“The Almanac maker predicts the weather, but another Maker makes the weather.”
Last winter, we were reminded on several occasions of the above axiom, penned many years ago by an anonymous source. Here at the Farmers’ Almanac, we take great pride in providing our readers with our annual long-range weather forecasts. While these prognostications are based on our time-tested “secret formula,” sometimes Mother Nature has a different scenario in mind.
This past winter (as much as we dislike admitting it) threw a knuckleball at our long-range outlook. Our long-range calculations forecast a winter of “clime and punishment,” with an active storm track bringing widespread and heavy doses of rain and snow to much of the country. They also called for above-normal temperatures to prevail over the southern and eastern U.S., with cold-to-very cold conditions for the Northern Plains and Northern Rockies into the western Great Lakes.
We did score a hit with the rather remarkable forecast for October 28-31, 2011. On October 29, 2011, a deepening storm system moved up the Eastern seaboard, interacted with an unusually chilly airmass, and snowflakes began to fall. It was a stormy period for the Northeast U.S., with copious rain and even snow over higher elevations and northern New England.
Our outlook of a balmy winter for the Southern and Eastern U.S. also worked out fairly well. For New England, New York, New Jersey, and Delaware, the winter of 2011—2012 ranked as either the second or third warmest winter in 117 years of available records. Massachusetts tied for its warmest February. It was the second warmest winter on record for Boston and New York; the fourth warmest for Washington, D.C., and Philadelphia.
But there were other places that also experienced some exceptional warmth. For Montana, the Dakotas, Minnesota and Wisconsin, it was one of the top ten warmest winters. For the 48 contiguous states, last winter turned out to be the fourth warmest winter since national records began in 1895!
As for precipitation, it seemed that we were off to an early start with that late October nor’easter. Then there was a major winter storm that brought blizzard conditions to parts of the Southern Rockies and Central Plains on December 19th and 20th (which we also successfully forecast). And we earnestly expected that there would much more to come once we fully settled into winter. But when it was all over, twenty-four states actually recorded below-normal, even much below-normal, precipitation for the winter.
Only ten states–chiefly across the nation’s midsection–recorded above-normal winter precipitation (Kansas recorded their seventh wettest winter).
We did forecast a wet winter for Texas which did indeed occur and, in fact, helped alleviate their severe drought, shrinking the total area affected from 43.3% in early December to 14.8% by the end of February. Conversely, California experienced its second driest winter on record, and the lack of precipitation limited snowpack growth, which subsequently led to the development of a drought there.
Across the Rockies and Great Plains, the snow cover ranked as the third smallest on record. This was in spite of the fact that February 2nd—4th saw a very heavy snowstorm that blanketed Colorado and Nebraska. Denver set a new snowstorm record for February of 15.9 inches (a storm, by the way, that we also had forecast). Even the Pacific Northwest was belted by hefty snow: Seattle recorded a record-shattering 6.8 inches of snow and ice on January 18th.
And as “meteorological winter” (the coldest three-month interval–Dec., Jan., Feb.) came to an end, a spring-like storm spawned straight-line winds, golf ball-sized hail, torrential rain, and at least 39 tornadoes from Nebraska east into Kentucky and Tennessee on February 28th–29th, causing significant damage and 13 fatalities.
So in a nutshell, we did forecast three of the biggest storms of the fall and winter season and correctly anticipated temperature and precipitation anomalies for some sections of the country, but overall we didn’t fare quite as well as we would have liked.
Spring and Summer
As winter turned to spring, and then summer, the situation worsened, with boiling temperatures across much of the country, coupled with the most severe drought conditions the nation has seen in more than 50 years. More than 1,300 counties have been declared disaster areas due to the heat and lack of precipitation.
The 2012 Farmers’ Almanac called for hotter-than-normal temperatures across much of the country, and very dry conditions for a large swath of the mountain and prairie states. The outlook also accurately predicted a wetter, stormier August for most areas along the East Coast.
Oscillations and La Niña
So what was the cause of this atypical winter weather pattern? It was a most unusual configuration of the jet stream over North America, allowed by the phenomena known as the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO), climate patterns that reflect differences in sea-level air pressures across our planet.
And the pressure differences this past winter were incredibly large. The NAO had the most extreme difference ever recorded in December, and the second most extreme for the Arctic Oscillation (both indices were categorized as “positive”). This pulled warm air up from the Southwest U.S. into the Eastern U.S., rather than allowing the usual flow of cold air down from Canada. With the Arctic oscillation in a positive phase this last winter, virtually all of the frigidly cold polar air spilled into the Eurasian Continent and Alaska (where January saw record cold and snow).
Then there was La Niña. When we have a La Niña situation like we did during the winter of 2011—2012, the main branch of the polar jet tends to stay well north, while the southern branch moves across the desert Southwest, the Southern Plains and the lower Mississippi Valley, bringing warmer temperatures. So in a sense, the unusually mild winter was something the wind blew in. La Niña and her even more tempestuous brother, El Niño, are opposite phases of ocean surface temperature variations in the Pacific.
Unfortunately, while meteorologists can reasonably anticipate an impending La Niña or El Niño some weeks or even months in advance, the same can’t be said for the NAO or AO variations; and in truth we don’t yet know why these variations happen. And our climate models are still too crude to make skillful predictions on how human-caused climate change might be affecting them. Some scientists also think there are links between solar activity and the times of positive values, and between arctic sea ice loss and the negative values, though such possible correlations are not fully clear.
But regardless of what the NAO or AO is doing or whether it’s a La Niña or El Niño winter, one thing is a constant: We have and always will utilize our own “secret formula” to develop our long-range weather forecasts.
What’s in store for this winter ahead? Be sure to check our web site next week when we release or official outlook.