On the night of November 22, 1997, the Cornell All-Sky Imager recorded a spectacular display of structure in the 630.0 nm emission over Arecibo, Puerto Rico. This event is an example of a phenomenon we have termed intense midlatitude spread F. In this paper we describe the stormtime geophysical conditions for the period and detail the evolution of the event. The daytime midlatitude ionosphere was disturbed for four consecutive days. The initial daytime doubling of the total electron content (TEC) was associated with equatorward propagation of a high-TEC patch that seemed to have associated composition changes. The following days had distinct diurnal double maxima (DDM). The TEC in the Caribbean was very high during the first night of the storm and was extremely structured. Airglow depletions and enhancements surged poleward, bifurcating numerous times in the process. The airglow depletions were collocated with TEC minima along similar lines of sight to Global Positioning System satellites. Eventually, four parallel and very similar airglow wave packets were visible and oriented at an angle similar to the less violent structures reported in the companion paper [Garcia et al., this issue> and moving slowly toward the southwest. We explore a number of possible explanations for these features. We are most confident that secondary instabilities of the generalized E¿B process can explain the evolution of the structures once they are formed. The initial process itself remains controversial. ¿ 2000 American Geophysical Union