Final answer:
The initial step in the CERT sizeup process after a tornado is to assess immediate hazards in the area to ensure the safety of both rescuers and potential survivors.
Step-by-step explanation:
The first thing you should do as you begin the CERT sizeup process after a tornado is to Assess immediate hazards in the area. This is critical to ensure the safety of rescue personnel and potential survivors. Hazards could include gas leaks, downed power lines, or unstable structures. Once the immediate hazards have been assessed and mitigated, you can then move on to identifying areas that might contain survivors, surveying the structural damage, and establishing communication with your team.