Sudden Stratospheric Warming and Anomalous U.S. Weather

Abstract

Severe distortion of tropospheric circulation is associated with major sudden stratospheric warming (SSW) events. This distortion consisting primarily of weakening of smaller-scale synoptic mats and development of strong blocking activity, is reviewed in the context of associated weather anomalies over the United States. Temperature, precipitation and cyclone anomalies of 17 January and February months experiencing SSW are contrasted with months of no stratospheric warming. The SSW is marked by intense cold, dry anomalies centered in the Ohio Valley, with below average temperatures covering the entire United States. In January, slight wet anomalies occur in the lee of the Rockies, and in February the desert southwest becomes quite wet. Cyclone activity decreases by 25% throughout the United States during SSW, most strongly along the West Coast and in association with the disappearance of the Colorado low. Storm track anomalies are documented over the eastern Pacific, the Gulf and Atlantic seaboard, and northeastern Canada. Slight variations of the anomaly patterns in February over the western United States are linked to the temporal evolution of SSW.