Daniel Swain in PBS: Millions are out of power in California, but were the PG&E shutoffs necessary?

Propelling this drying-out process are the Diablo and Santa Ana winds, which start east of California. Autumn is the start of cold, low-pressure storms over the Great Basin, several thousand feet up in Nevada and Utah.

As they move, these winter storm systems “leave behind cold air and are replaced by surface high pressure,” said Daniel Swain, a climate scientist at the UCLA Institute of the Environment and Sustainability.