Time sequence of image cutouts defined by the subfield frame in Fig. 1. The row number and the observing moment of each row are specified in the first panel of each row. Columns: Hα images at Δλ = −0.8 Å from line center (SST), Hα line center (SST), 1400 Å slitjaw (IRIS), He II 304 Å (AIA), Fe XII 193 Å (AIA). The four numbered arrows mark the location of the tip of the dark extending precursor streak defined successively for the first four Hα blue-wing panels. Each frame is bytescaled individually. Row 6 corresponds to Fig. 1. The IRIS slit is visible in the top two and bottom two 1400 Å panels.