1000-year storms in South Carolina

Monday October 12, 2015

Homeland Security Watch has an excellent post on the recent claims that South Carolina has faced at 1000-year storm. Focusing on the annual exceedance probability (AEP), the story post throws a bit of a damper on it.

The post quotes an awful editorial in the Charleston Post and Courier:

Catastrophic rainstorms like this one happen only every thousand years, climate and weather experts explained as unprecedented flooding forced people out of their homes, closed roads and submerged stalled vehicles. One can only hope that assessment holds true… We must work to prepare for the next disaster, even if it doesn’t happen for a thousand years.

That is a complete misunderstanding of the AEP. The AEP provides a probability, not an interval. A storm like this is just as likely tomorrow as it was yesterday. Nothing will prevent one from coming again before a thousand years are up. As many, including HSW, have pointed out, these storms and floods are likely to become more frequent as global climate change distorts long term weather patterns.

Image by United States Air National Guard / Wikimedia.