  Information flow during catastrophic events is a critical aspect of disaster
management. Modern communication platforms, in particular online social
networks, provide an opportunity to study such flow, and a mean to derive
early-warning sensors, improving emergency preparedness and response.
Performance of the social networks sensor method, based on topological and
behavioural properties derived from the "friendship paradox", is studied here
for over 50 million Twitter messages posted before, during, and after Hurricane
Sandy. We find that differences in user's network centrality effectively
translate into moderate awareness advantage (up to 26 hours); and that
geo-location of users within or outside of the hurricane-affected area plays
significant role in determining the scale of such advantage. Emotional response
appears to be universal regardless of the position in the network topology, and
displays characteristic, easily detectable patterns, opening a possibility of
implementing a simple "sentiment sensing" technique to detect and locate
disasters.
