  The X-ray transient source Sw J1644+57 recently discovered by Swift is
believed to be triggered by tidal disruption of a star by a rapidly spinning
supermassive black hole (SMBH). For such events, the outer disk is very likely
misaligned with respect to the equatorial plane of the spinning SMBH, since the
incoming star before disruption most likely has an inclined orbital plane. The
tilted disk is subject to the Lense-Thirring torque, which tends to twist and
warp due to the Bardeen-Petterson effect. The inner disk tends to align with
the SMBH spin, while the outer region tends to remain in the stellar orbital
plane, with a transition zone around the Bardeen-Petterson radius. The
relativistic jet launched from the spinning SMBH would undergo precession. The
5-30 day X-ray lightcurve of Sw J1644+57 shows a quasi-periodic (2.7-day)
variation with noticeable narrow dips. We numerically solve a warped disk and
propose a jet-precessing model by invoking a Blandford-Znajek jet collimated by
a wind launched near the Bardeen-Petterson radius. Through simulations, we show
that the narrow dips in the X-ray lightcurve can be reproduced for a range of
geometric configurations. From data we infer that the inclination angle of the
initial stellar orbit is in the range of $10^{\circ}-20^{\circ}$ from the SMBH
equatorial plane, that the jet should have a moderately high Lorentz factor,
and that the inclination angle, jet opening angle, and observer's viewing angle
are such that the duty cycle of the line-of-sight sweeping the jet cone is
somewhat less than 0.5.
