On the inverse relationship between North American snow extent and North Atlantic hurricane activity

Abstract

AbstractThe statistically significant inverse relationship is examined between North American snow cover extent during January and North Atlantic hurricane activity during the following hurricane season. To better quantify this relationship the long‐term trend and ENSO years were removed from the data. The lightest January snow‐cover years (LSY) show sharp increases (40–90%) compared to the heaviest January snow‐cover years (HSY) in nearly all measures of Atlantic hurricane activity, including the numbers and duration of hurricanes and major hurricanes, and the average seasonal accumulated cyclone energy (ACE) index. Approximately, half of the LSY events featured above‐normal hurricane seasons and none were below‐normal, while approximately half of the HSY featured below‐normal hurricane seasons none were above‐normal. Composite analyses indicate the anomalous wintertime snow‐cover extent and Atlantic hurricane activity are linked through their common association with persistent and hemisphere‐wide extratropical circulation anomalies tied to the Arctic Oscillation (AO). The LSY are associated with a positive phase of the AO, along with warmer surface temperatures in both North America and Eurasia, while the HSY are associated with a negative phase of the AO and below‐average continental surface temperatures. One unresolved issue is the extent to which the anomalous snow extent feeds back onto the large‐scale circulation so as to help maintain the wintertime AO patterns through the spring and summer. Another remaining issue is the process(es) by which the extratropical AO signals eventually penetrate into the tropics so as to influence Atlantic hurricane activity. Copyright © 2012 Royal Meteorological Society