This paper is a continuation of established research displaying relationships between large-scale circulation anomaly indices, such as the North Atlantic Oscillation (NAO), El Nino-Southern Oscillation (ENSO), and Pacific-North American (PNA) pattern, and extended wintertime (DJFM) climate variability in the northeastern United States. An additional focus on the possible interrelated effects of each circulation pattern with the occurrence and frequency of previous Nor’easter type winter storms is also considered.

Daily and/or monthly time-series were collected for each of the large-scale circulation anomaly indices. Station data were collected from locations throughout the northeastern states, from Boston, MA to the north, Washington, D.C. to the south, and Pittsburgh, PA to the west. Historical data for all Nor’easters were also gathered. All data range from 1950 to 2001 and are limited to the extended winter months (DJFM), when variability in climate is most pronounced.

Composite analyses and a linear regression technique are utilized to determine the statistically significant relationships between large-scale circulation patterns, temperature and precipitation anomalies with incidences of extreme events, and Nor’easter occurrences. The interaction between the NAO and ENSO and its resultant effects on climate variability is also considered.