Near the end of 2012, the US Army Corps of Engineers released 28,000 acre-feet of water from Lake Mendocino. Then followed 14 of the driest months on record. The key to managing the drought and deluge cycle of California lies in a better understanding of atmospheric rivers, intense winter storms that transport water from the tropics to the West Coast. Over the last decade California has pumped more than $40 million into the statewide network that tracks these rivers, giving lead times of up to a week.