Figure 4: Phase trajectories for the 500-hPa heights in the central part of the blocking region for July 2010 for the (a) planetary-scale, and (b) synoptic-scale, during the preblock (solid, red—X), the block lifecycle (dots, blue—o), and decay (dash, green—diamond). The trajectory begins at (S) and ends with (E), and the block onset is marked with (O) and termination with (T). The dates are labeled as month/day.