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This paper reports the results of experimental investigations on laboratory-scale fire whirls. We generated fixed-frame type fire whirls of a methanol pool fire, measured tangential and radial velocity distributions near the flame base, and observed the changes in flame height and flame-base shape under three different flow conditions. We compared these conditions in order to understand the relation between the flame height and vortex structure and the mechanism of flame height increase. It is proposed to use the degree of closeness of flame to liquid fuel, a, defined based on the approximation of flame-base shape using a parabolic function, to correlate flame height; it was observed that the quantity a had a certain relationship with the flame height. In addition, it was experimentally found that the radial velocity distribution near the flame base had a significant influence on the flame height because the radial inflow makes the flame shape thinner resulting in a concave flame shape near the base which increases the heat flux to the liquid surface, thereby increasing the evaporation rate of liquid fuel.