Reliable correlation of simultaneously measured resistively, susceptibility and specific heat critical parameters of hole-underdoped YBCO permitted to establish a phenomenological model of normal-superconductor transition. After the model, fluctuations of quasifree electrons drives at T * ) T C the appearance of paired charge carriers (pseudogap-PG) characterized by partial coherence of the order parameterÕs phase. The evolution of PG state from T * $ 140 K to the critical temperature T C $ 92 K is connected to the average increase of the statistically distributed partial coherence lifetime (from s $ ps to 1) and coherence length (from k $ nm to 1) of the fluctuating precursor islands. In this dynamic process the specific heatÕs maximum signals (at temperature T CC $ 93.6 K) the appearance of the first mesoscopic coherent islands. T C marks the percolation of these islands. We believe that the presented concept of dynamical evolution (in coherence time and space from 0 to 1) of the paired charge structures is a promising scenario while describing the properties of hole doped high-T C superconductors between the temperatures T * and T C .