The Zhang-Gal-Chen single-Doppler velocity retrieval (ZG) method was applied to the 26 January 1999 squall line monitored by the S-POL weather radar during the WET AMC and TRMM LBA field experiment campaign in Rondônia, Brazil. Sensitivity analyses were performed for variable area sizes and weights of the cost function that conserves the reflectivity and the radial wind field in a moving reference frame. The retrieved wind fields by the ZG method were compared to the ones retrieved by two weather radars, namely, the S-POL and the TOGA radars. Results indicate that it might be difficult to specify the reference frame moving with the weather system. The effect of the drop terminal velocity prevented adequate retrieval of the vertical component of the wind field.