California No Stranger To Severe Weather
November 2, 2012

Future Severe Weather Systems A Concern For California

Brett Smith for - Your Universe Online

In the wake of Hurricane Sandy, climatologists from the University of California at Merced are warning that the West Coast could be in line for a superstorm of its own.

“We can see very big storms, and there are a couple of issues related to climate change to think about,” said Roger Bales, director of the Sierra Nevada Research Institute at UC Merced. “Most of our biggest storms are snow storms, which builds up snowpack in the mountains. The snowpack is a reservoir, storing water that will be used throughout the year across the state.”

“But if you warm the climate,” he added, “those storms become rain events — there´s more immediate runoff, less water storage, and the rain will actually melt some of the existing snowpack.”

The combination of heavy rains and melting snowpack could create a nightmare situation, involving heavy flooding and massive landslides.

Perhaps one of the biggest causes for concern, scientists say, is the Pineapple Express, a weather phenomenon that drives atmospheric moisture across the Pacific and into the West Coast from an area near Hawaii. These so-called “atmospheric rivers,” like the Pineapple Express, have caused trouble for Californians in the past and are capable of more localized, but severe damage.

“We have very large storms that cross into California and affect our region — not with the same widespread damage as Hurricane Sandy, but with water and wind that are comparable to hurricanes and tornados,” said Robert Rice, a UC Merced scientist with the SNRI.

As an example, Rice cited a localized storm from November 2011 that had sustained winds higher than 100 mph and gusts greater than 150 mph, which compares to Category 3 or 4 hurricanes.

“These storms would be very destructive and costly to urban areas,” Rice said, “and they are more frequent than most people imagine. Not much attention is focused on them because they rarely affect large urban populations, more often being restricted to the Sierra.”

Another weather phenomenon that could result in deadly storms impacting California and the West Coast is El Niño. According to the National Oceanic and Atmospheric Administration (NOAA), El Niño is characterized by above average temperatures along the equatorial Pacific Ocean. If these higher temperatures become extreme, they can cause both severe drought and flooding conditions over the course of several months.

“A strong El Niño means Northern California and the Pacific Northwest have a greater chance of below-normal precipitation, Southern California and the Southwest have a greater chance of above-average precipitation, and the center of the state has equal chances of either,” Bales said. “But with a weak El Niño or neutral condition, either above or below normal conditions could prevail across the state.”

The wildly fluctuating moisture conditions means that the communities living in these effect areas need to prepare not only for extreme storm conditions, but also for extreme heat and the problems that come with it.

Besides being a potential flood threat, the California snowpack melt is a necessary water supply for the state. Any combination of extreme weather events that directly impact the snowpack might have to be managed properly by either a relief effort or the water supply facilities.