ESRL Quarterly Newsletter - Spring 2010

Washington's Weird Winter

NOAA assessment implicates NAO and El Niño

U.S. Capitol with snow.

Explanations for the record-breaking snows that paralyzed the Mid-Atlantic this winter were as diverse as they were bizarre: An inauspicious alignment of the stars; global warming; global cooling.

But NOAA's Climate Scene Investigators (CSI), a team of “attribution” experts from around the agency, have identified the most usual of suspects: the ordinary ups and downs of weather.

The North Atlantic Oscillation and El Niño are normal climate cycles, both sources of natural weather variation. This winter, the two conspired to cripple the Mid-Atlantic with snow. Dec. 19, a massive snowstorm hit the U.S. mid-Atlantic, laying down more than 20 inches of snow in some places. The storm set new records for December snowfall, and there was more to come. Another major snowstorm struck the region on Feb. 6, 2010, and then a third storm swept in with blizzard conditions just four days later.

CSI, led by ESRL's Marty Hoerling (Physical Sciences Division) assembled to analyze possible causes and quickly identified the two main suspects—North Atlantic Oscillation (NAO) and El Niño—already known to be at large. The team's work is featured on (“Forensic Meteorology Solves the Mystery of Record Snows”), and a full scientific analysis of the storms will be posted at