In the immediate aftermath of a disaster routine processes, even if specifically designed for such a situation, are not enacted blindly. Actions and processes rather adapt their behavior based on observations and available information. Attempts to support these processes by technology rely on process models that faithfully capture process execution and adaptation. Based on experiences from actual disaster response settings, we propose to specify an adaptive process as a set of scenarios using a Petri net syntax. Our operational model provides an adaptation operator that synthesizes and adapts the system behavior at run-time based on the given scenarios. An example illustrates our approach. Key words: process model, adaptation, scenarios, Petri nets, disaster response