Fig. 6: Composite precipitation distributions of squall-line and non-squall-line tropical cyclone rainbands (TCRs) during and before their formation.

The spatial composite of precipitation frequency (>15 dBZ, color shading) and normalized radial distance by the radius of maximum wind (RMW, contour) with respect to the location of each outer TCR (x = 0 km, y = 0 km) for 303 squall-line TCR cases at (a) 1 h prior to the preformation time (t₀-2), (b) the preformation time (t₀-1) and (c) the formation time (t₀). d–f as in (a)–(c), but showing the composite results for 140 non-squall-line TCR cases. For the composites at t₀-1 and t₀ -2 in (a), (b), (d) and (e), the location of each TCR case is determined by the backward extrapolation from the TCR location at the formation time (i.e., t₀) based on the calculated propagation velocities of TCRs.