(a) Example for applying the WG_M method to two smaller (M1.2 and M1.9) GOES M-class flares in AR 11504. The top panel shows the WG_M, the middle panel plots the distance between the barycentres, and the bottom panel is a plot of the associated unsigned magnetic flux as a function of time. The M1.2 and M1.9 flares are indicated by (blue) vertical lines where the value of the is taken. Note the U-shapes (red parabolae) in the middle panel that are key flare precursors of the WG_M method. The error is marked with shaded grey. (b) Top/middle and bottom panels are the related intensity/magnetogram maps and the associated Debrecen data catalogue representation of synthetic polarity drawing of AR at 01:59 on 13 June 2012. The red circle shows which umbral area and mean field strength are taken to calculate WG_M.