Is a 'Superstorm' the Next 'Big One' for California?

For years, California residents have worried about warnings from the U.S. Geological Survey that someday the state will be hit by a giant earthquake known as the "big one." Now the agency is warning of a new type of big one -- a "superstorm."

The USGS says California could experience what it calls the "ARkStorm Scenario," a potential meteorological pattern that could produce weather of epic proportions, including up to 10 feet of rain, extensive flooding and more than $300 billion in damage. It's estimated that one-quarter of the homes in California would be affected by some sort of flood damage in this scenario.

The goal of the analysis is not to generate fear but to prepare residents and emergency personnel for what could be the worst-case scenario from a meteorological perspective. The project is part of the National Real-Time Flood Mapping initiative to improve national flood management.

The massive ARkStorm is considered a plausible weather scenario based on previous flood records, including modern and prehistoric, along with projected climate-change projections.

Extreme weather patterns are common in California, and when established, the weather patterns often produce a nearly nonstop barrage of storms for days or weeks on end, resulting in excessive low-elevation rainfall and mountain snow in a topography especially susceptible to mudslides and flash flooding.

The hypothetical extreme scenario laid out by USGS scientists combines the effects of putting two extreme weather events that have already happened -- in January 1969 and February 1986 -- back to back.

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As such, the USGS considers the event to be within the realm of possibility.

Such intense stormy periods are often associated with an ongoing El Nino, which can add intensity and moisture to storms bound for California. The storms are typically called the "Pineapple Express" when the moisture originates in the tropical regions near Hawaii. However, extreme weather patterns can happen in the absence of an El Nino as well.

Dramatic weather -- and intense precipitation -- has occurred in California during the past two winters, largely eliminating what had been a multiyear drought. Just last month, a weeklong storm dumped 5 to 20 inches of rain across a large portion of the state, including more than 16 feet of snow in the ski resorts of the high Sierra.