Changes in the Frequency and Synoptic Causes of Anomalously Warm January Days in the Interior Northeastern USA

The frequency of anomalously warm January daily maximum temperatures in the Northeast has increased over the past 60 years. This study focuses on the increase in warm maximum temperatures in the region and possible causes for this change. The January maximum temperature data for this region show an increase in the warmest maximum temperatures, but not a direct shift in the overall distribution of daily maximum temperatures. This study focuses on the possible reasons for the increase in the frequency of the warmest temperatures in recent years even while the overall temperature distribution has not moved as dramatically towards warmer temperatures.

A principal components analysis (PCA) is used to analyze the synoptic conditions on days on which anomalously warm maximum temperatures occurred. The PCA is used to determine whether the strength or frequency of the pattern that leads to warm January days in the interior Northeast has changed, or if the synoptic conditions leading to the warmest days has stayed consistent over time, but in recent years has resulted in more anomalously warm days. The statistical analysis in this study will describe the effect that the synoptic pattern has had on the increase in warm January maximum temperatures in the Interior Northeast.