Like a cantankerous child, El Niño rightfully deserves a lot of blame for a lot of weather hardships around the world, but don't blame it for this woeful bout of cold temperatures gripping the United States. For this nasty weather, blame the natural variability of winter.
The warmer-than-normal sea surface temperatures spreading across the central and eastern equatorial Pacific — the footprint of El Niño — more commonly has the opposite impact, in fact, bringing higher temperatures across the northern states, which currently are experiencing the most severe cold.
(The graph, from the National Weather Service, shows the pattern of upper ocean equatorial Pacific temperatures, as departures from normal, over the year.)
The most obvious impact of El Niño conditions on the contiguous United States is the effect it has on the powerful flow of high-altitude winds known as the jetstream. El Niño pulls the jetstream farther south than usual over the course of the winter, and along with it the track of winter storms.
The especially cold conditions across the country suggests that those patterns haven't set in yet — although climate scientists always point out weather and climate operate on different timescales — the atmosphere is just naturally variable — and you can't attribute a single storm to climate conditions.
The current El Nino advisory issued this week by the National Weather Service Climate Prediction Center described an El Niño of "moderate strength" and had this to say: "For the contiguous United States, potential impacts include above-average precipitation for the southern tier of the country with below-average precipitation in the Pacific Northwest and the Ohio and Tennessee Valleys. Below-average snowfall and above-average temperatures are most likely across the northern tier of states (excluding New England), while below-average temperatures are favored for the southeastern states."
Notwithstanding these frosty days, there's plenty of winter season remaining for these typical El Niño patterns to take hold.
