Teleconnections and Great Lakes Extratropical Cyclones: Is There a Correlation, and Does it Trend with our Changing Climate?

Extratropical cyclones (ETCs) play an important role in the weather and climate in the Great Lakes Region (GLR), particularly during the cold season (October – March). Using a historical dataset of Great Lakes ETCs, previous research has shown that the storms are getting warmer and wetter at a rate faster than the background climate, despite large inter-annual variability. The variability in Great Lakes ETC activity has not yet been explored, and it is hypothesized that global teleconnection patterns play a significant role in visible ETC trends. This study investigates the role of global teleconnections on GLR ETCs in two ways: (1) it determines if there are significant differences in ETC characteristics between the positive and negative phase of different teleconnections, and (2) identifies potential trends within each phase over the course of the study period.

The Great Lakes ETC dataset is compiled using ERA5 reanalysis from cold seasons between October 1959 and March 2021. Five spatially-averaged variables are extracted from the ETC at the moment of lowest recorded pressure for each storm. These variables are then analyzed against five different teleconnections: El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), North Pacific Gyre Oscillation (NPGO), Pacific Decadal Oscillation (PDO), and Pacific-North America Pattern (PNA). Storms are grouped based on teleconnection phase, and it is determined that both spatial and temporal ETC trends are significantly correlated with certain teleconnections. Results show that GLR ETCs are often correlated with PNA patterns, and that NPGO could also explain the variance in some trends. There is no consistent significant correlation found between GLR ETCs and ENSO.