  Using the radio observations by FIRST and NVSS, we build a sample of 151
radio variable quasars selected from the Sloan Digital Sky Survey Data Release
3 (SDSS DR3). Six (probably another two) among them are classified as broad
absorption line (BAL) quasars, with radio flux variations of a few 10 percent
within 1.5-5 years. Such large amplitudes of the variations imply brightness
temperatures much higher than the inverse Compton limits (10$^{12}$ K) in all
the BAL quasars, suggesting the presence of relativistic jets beaming toward
the observer. The angle between the outflow and the jet is constrained to be
less than $\sim 20^{\circ}$. Such BAL quasars with polar outflows are beyond
the simple unification models of BAL quasars and non-BAL quasars, which
hypothesize that BAL quasars are normal quasars seen nearly edge-on.

Astrophysics