The average groundhog has more sex appeal than meteorological skill, yet every year we haul their furry hides out of their dens so we can pose our most vexing long-range forecast question.
“So, if the groundhog sees his shadow, does this mean we get six weeks of winter?” as my friend from western Massachusetts posted on Facebook last week. Usually we wonder whether spring will come early, but my friend, who likes to cross-country ski, is not alone in wondering whether winter will truly arrive at all this year.
A large swath of the Northeast saw its heaviest snowfall of the season thus far in October, in a freak pre-Halloween storm that proved to be just a tease. There has been precious little of the white stuff since then and not much weather that could truly be called “cold” by the standards of the region.
Or for most of the lower 48 states, for that matter. The vast stretch of territory from the Rockies to the East Coast has seen only a few intrusions of Arctic air, most of which quickly moved eastward into the Atlantic Ocean. Snow cover has been scant almost everywhere east of the Mississippi, even in the snow belts downwind of the Great Lakes. The Southwest has had a few storms, including the blizzard that dropped around two feet of snow in the Colorado Rockies late last week, and the Pacific Northwest has gotten its share of snow, even down to the lowlands around Seattle. But barring a rapid turnaround, most Americans are likely to remember this as a mild winter, if they remember it at all.
The funny thing about weather is that we perceive it locally at a particular point in time, but it happens everywhere all the time. We tend to be mistaken when we generalize from isolated but extreme events that happen to us. A lot of people, for example, blamed last April’s severe tornado outbreak in the Southeast on global warming. That’s probably wrong. Although a couple of extreme outbreaks in the spring of 2011 in the South made it a near-record year for U.S. tornadoes, other parts of the country that experience twisters, such as the northern Great Plains, did not find 2011 particularly severe. We probably will see a milder year in the South in 2012. This does not mean global warming has not reached the northern Plains, or that it suddenly went away after 2011. It just mean that extreme events happen in particular localities for all sorts of meteorological reasons, many of which have been around since long before humans lit their first campfire.
In Alaska, this winter is going to be remembered for a long time. There was the dramatic rescue of the city of Nome, which was at risk of running out of fuel until a Russian tanker, escorted by a U.S. Coast Guard icebreaker, relieved the town after weeks of slogging through the frozen Bering Sea. There was a superstorm, an “arctic hurricane,” right at the start of the cold season in November. December reversed the pattern and was warm for much of the state, but January brought a month-long deep freeze.
In Nome it was the coldest January on record, with an average temperature of nearly 17 degrees below zero Fahrenheit, which is 22 degrees below normal. The records at Nome go back to 1907. Fairbanks had its coldest January in 40 years, and fifth-coldest in records going back to 1904, with an average of minus 26.9 and a low of minus 51. Galena, in the northwestern part of the state, had its coldest month on record at minus 32.6, and had four consecutive days when the temperature dropped to minus 60 or lower, including minus 65 on Jan. 29.
Blizzards and storms repeatedly swept across the southern part of the state, from the usually mild Aleutians to the Panhandle. Kodiak, in south-central Alaska, received a record four feet of snow during the month and had the third-coldest January in records going back to the 1890s, with an average temperature of 21.4 degrees.
Severe cold gripped eastern Europe and adjacent Russia last week, and the cold spread into western Europe following a generally mild season. Residents of western Japan battled extreme snowfalls, much of which resulted from “ocean effect” as frigid Siberian air masses crossed the mild waters of the Sea of Japan.
It would be nice to think that our meteorologists, armed with sophisticated computer models and a worldwide data network, are significantly better than a groundhog when it comes to long-range forecasting. To be fair, they are. By constantly monitoring ocean temperatures and wind anomalies across the globe, specialists at places like the U.S. Climate Prediction Center can boast significant skill at forecasting El Nino or La Nina conditions months in advance. These changes in the temperature of Pacific Ocean waters have global weather impacts, so meteorologists could accurately predict that Florida could expect a drier than average winter this year, thanks to La Nina.
But temperature oscillations in the Pacific Ocean are not the only driver, or even the most important driver, of our weather - especially in winter. The North Atlantic Oscillation often has a greater impact on what happens to people in eastern North America and western Europe. When the NAO is negative, as it was last winter and the one before, frigid air is shunted southward, and big population centers like London and New York often have to break out the road salt. When it is positive, as it generally has been since November 2011, fast-moving winds in the upper atmosphere keep the deep cold bottled up in the North American arctic or shift it across the pole toward Asia. Meanwhile, milder air originating over the Pacific Ocean floods across North America. This can bring a lot of precipitation to the Pacific Northwest, but for most of the country it yields milder than average conditions.
Climate scientists have little skill at forecasting the NAO more than several weeks in advance. As a result, their forecasts for northern hemisphere winters can be right about the big picture of El Nino and La Nina, but wrong about the critical details of whether a given region will see many cold air masses or frequent storms. Not surprisingly, researchers are searching for ways to predict the NAO at longer time horizons, studying factors like the speed at which snow cover spreads across Siberia in early autumn to determine whether Washington, D.C., can expect icy sidewalks in February.
In the meantime, we have to work with what we’ve got. For many of us, that’s a sleepy groundhog. I have a better forecaster (and one who is considerably cuter than a groundhog): my wife Linda, whose birthday is today. Linda, who was raised in Queens, N.Y., observes that it usually snows there on or close to her birthday. Sure enough, the computer models today are pointing to a change in the NAO and the possibility of frosty weather in the near future.
Happy birthday, Linda. As for you groundhogs, sweet dreams. See you in the spring.