  The physical properties of galactic molecular outflows are important as they
could constrain outflow formation mechanisms. We study the properties of the
southwest (SW) outflow streamer including gas kinematics, optical depth, dense
gas fraction, and shock strength in the central molecular zone of the starburst
galaxy NGC 253. We image the molecular emission at a spatial resolution of
$\sim$27 pc based on data from the ALCHEMI program. We trace the kinematics of
molecular gas with CO(1-0) line. We constrain the optical depth of CO emission
with CO/$^{13}$CO(1-0) ratio, the dense gas fraction with HCN/CO(1-0) ratio, as
well as the shock strength with SiO(2-1)/$^{13}$CO(1-0) ratio. The
CO/$^{13}$CO(1-0) integrated intensity ratio is $\sim$21 in the SW streamer
region, which approximates the C/$^{13}$C isotopic abundance ratio. The higher
integrated intensity ratio compared to the disk can be attributed to the
optically thinner environment for CO(1-0) emission inside the SW streamer. The
HCN/CO(1-0) and SiO(2-1)/$^{13}$CO(1-0) integrated intensity ratios both
approach $\sim$0.2 in three giant molecular clouds (GMCs) at the base of the
outflow streamers, which implies the higher dense gas fraction and enhanced
strength of fast shocks in those GMCs than in the disk. The contours of those
two integrated intensity ratios are extended towards the directions of outflow
streamers, which connects the enhanced dense gas fraction and shock strength
with molecular outflow. Moreover, the molecular gas with enhanced dense gas
fraction and shock strength located at the base of the SW streamer shares the
same velocity with the outflow. These phenomena suggest that the star formation
inside the GMCs can trigger the shocks and further drive the molecular outflow.
