Traditional spaghetti plots from ensemble data provide no explicit information as to the uncertainty of the realization flow paths. While intuitive assessment can be used when visualizing streamline density directly in such a plot, the display is often cluttered and difficult to interpret. The authors present a method to measure uncertainty and visualize member streamlines from an ensemble of vector fields. The method incorporates velocity probability density as a feature along each member streamline. The authors show visualizations of two different data sets using the proposed method.