Fig. 2: Impacts of the North Pacific wave interference on the North American cold and precipitation extremes.

Pentad composites of changes in the frequency of occurrence (%) relative to the climatological frequency of occurrence of (A–D) cold extremes (5th percentile of daily minimum temperature) and (E–H) heavy precipitation extremes (95th percentile of daily precipitation) averaged over (A, B, E, F) lag days −2 to +2, and (C, D, G, H) +3 to +7 for (A, C, E, G) (left) constructive interference events and (B, D, F, H) (right) destructive interference events. Stippling indicates statistical significance (p < 0.05) evaluated by Monte Carlo simulations. Boxes denote the domain of Alaska and western Canada (Red; 55°–70°N, 167.5°–107.5°W), western U.S. (Green; 30°–50°N, 126.25°–106.25°W), central U.S. (Yellow; 35°–55°N, 106.25°–86.25°W), and continental U.S. (Purple; 30°–50°N, 126.25°–66.25°W).