Here it is only the middle of February, and several cities in the mid-Atlantic region of the United States (Washington, D.C., Baltimore, Philadelphia) have set new records for annual snowfall accumulations. We could wonder if the snow is on steroids, but as that doesn’t make sense, we have to look elsewhere. The meteorologists have an answer, blaming it on the convergence of cold from a high-latitude blocking pattern (or negative Arctic Oscillation) and moisture from the Pacific Ocean’s El Niño—global forces in action!
As noted in a previous blog entry:
The number for interdisciplinary works on snow is 551.5784 Snow, under 551.57 Hydrometeorology. Comprehensive works on snowstorms go at 551.555 Snowstorms ("Class here blizzards"), under 551.55 Atmospheric disturbances and formations; while works on the social problems caused by snowstorms, and the social services provided in response, are classed at 363.34925, adding to base number 363.3492 (Disasters caused by weather conditions) the number 5 that follows 551.55 in 551.555.
In this blog entry, we’ll further explore the classifying of subjects on the weather side of our recent epic snowstorms; a subsequent blog entry will explore various ramifications of the snow, including specific social services rendered in response to the storms.
As explained in a story on National Public Radio (NPR),
the Arctic Oscillation refers to shifts in atmospheric pressure over the Arctic and the middle latitudes of the earth. In its positive phase, atmospheric pressure decreases over the Arctic and increases over the mid-latitudes. In the Arctic Oscillation's negative phase, it's just the reverse. Pressures are relatively high over the Arctic and relatively low over the mid-latitudes.
Comprehensive works on sea-level atmospheric pressure shifts of this sort should be classed in 551.543 Atmospheric pressure variations over time at earth's surface. But a do-not-use note at 551.54309 instructs us to class geographic treatment of such pressure variations in 551.5409. The number for the Arctic Oscillation is thus 551.5409113 (built with 551.54 Atmospheric pressure, plus T1—091 Treatment by areas, regions, places in general, plus 13, the numbers following 1 in T2—113 Arctic regions, following instructions at T1—091). Works on the effects of El Niño’s warming of equatorial Pacific Ocean surface waters should be classed in 551.52464 Pacific Ocean-atmosphere interactions (built with 551.5246 Ocean-atmosphere interactions, plus 4, the number following T2—16 in T2—164 Pacific Ocean, following instructions at 551.52463–551.52467); note the Relative Index term Ocean temperatures—meteorological effect at 551.5246.
Given the extreme meteorological conditions of this winter, how accurate have the weather forecasts been? Three to four days before each of the major snow events of the winter, we had but little hint of how big the storm would turn out to be, although we generally had a good idea that we would receive some snow as of a certain day. As the snow day approached, the ranges predicted became increasingly more accurate. Methods of forecasting snow are classed in 551.64784 (built with 551.64 Forecasting of specific phenomena, plus 784, the numbers following 551.5 in 551.5784 Snow, following the instruction at 551.641–551.647).