I will discuss the likely solar wind and magnetospheic drivers for a group of storms with uncharacteristically low thermosphere density response given the level of energy input suggested by standard magnetic indices. The characteristics of these anomalous storms are: 1) multi-hour, pre-storm solar wind density enhancement accompanied by neutral to northward interplanetary magnetic field (IMF) and slightly elevated solar wind speed; 2) a subsequent interval of solar wind dynamic pressure increase and southward IMF that trigger excess energy particle flux to the upper atmosphere; 3) enhanced production of thermospheric nitric oxide (NO) by precipitating particles and storm heating; and 4) NO infrared cooling and damping of thermospheric expansion. In a group of control storms from the same time frame these features are absent or muted. I will discuss the roles of solar wind “quiet before the storm,” magnetospheric pre-conditioning and solar cycle dependency in the problem storms. These problem neutral-density storms reveal an element of “geo-effectiveness” that is difficult to quantify with indices and perhaps even with upstream solar wind data.