Abstract: The winter of 2014/15 brought record snow totals to portions of southeastern New England. Additionally, over 90% of Boston Logan Airport snowfall during the winter fell during phases 7 and 8 of the Madden–Julian oscillation (MJO) index. This motivated Klotzbach et al., Monthly Weather Review, 2016 to investigate potential connections between intense southeastern New England snowstorms and the MJO in the historical record. It was found that southeastern New England snowfall, measured since the 1930s at several stations in the region, recorded higher than average winter snowfalls when enhanced MJO convection was located over the western Pacific and the Western Hemisphere (phases 7–8). Similarly, snowfall was suppressed when enhanced MJO convection was located over the Maritime Continent (phases 4–5). The MJO also modulates the frequency of nor’easters, which contribute the majority of New England’s snowfall, as measured by reanalysis-derived cyclone tracks. These tracks were more numerous during the same MJO phases that lead to enhanced snowfall, and they were less common during phases with less snowfall.

• The modulation of extra-tropical cyclones by the MJO:
  
  

  Figure 1: Anomalous extratropical cyclone track density stratified for MJO phases (top) 7 and 8 and (bottom) 4 and 5 overlaid with track climatology (contours) for the 1950–2011 period.

• Which is reflected in a modulation of the likelihood of snowfall in southeastern New England:
  
  

  Figure 2: The change in the probability of DJF snowfall in southeastern New England by MJO phase relative to the baseline probability over the 1936–2011 period. Results for individual stations are indicated by circles and the mean across all stations is indicated by the large square; station results not statistically significant at the 5% level are denoted with ‘‘3.’’ Statistical significance was calculated using a Monte Carlo technique whereby the MJO phases are randomly shifted relative to the snowfall time series 1000 times and the composites recomputed.