Thread: Mysterious Atmospheric River Soaks California, Where Megaflood May Be Overdue

Mysterious Atmospheric River Soaks California, Where Megaflood May Be Overdue

By Mark Fischetti | Scientific American – 7 hrs ago

Northern California is experiencing the first days of what weather forecasters are warning will be a long series of torrential rainstorms that could cause serious flooding across the northern one-third of the state.

The relentless storms are being driven by a feature in the atmosphere you have probably never heard of: an atmospheric river. Oh, and another atmospheric river created the worst flooding since the 1960s in western England and Wales this past week, where more than 1,000 homes had to be evacuated. An atmospheric river is a narrow conveyor belt of vapor about a mile high that extends thousands of miles from out at sea and can carry as much water as 15 Mississippi Rivers. It strikes as a series of storms that arrive for days or weeks on end. Each storm can dump inches of rain or feet of snow.

For more details, see this feature story that Scientific American has just published, written by two experts on these storms. Scientists discovered atmospheric rivers in 1998 and have only recently characterized them fully enough to allow forecasters to warn of their arrival.

They can strike the west coasts of most continents, but California seems to be a prime target. As many as nine small atmospheric rivers reach the state each year, each lasting two to three days, including the famous "pineapple express" storms that come straight from the Hawaii region of the Pacific Ocean.

Ironically, although the storms are dangerous, they are also vital; they supply 30 to 50 percent of California's rain and snow--in the span of about 10 days a year.

Megaflood Overdue? The real scare, however, is that truly massive atmospheric rivers that cause catastrophic flooding seem to hit the state about once every 200 years, according to evidence recently pieced together (and described in the article noted above). The last megaflood was in 1861; rains arrived for 43 days, obliterating Sacramento and bankrupting the state.

The disaster is largely forgotten, but the same region is now home to more than six million people. Simulations of a 23-day storm there indicate that more than $400 billion of damage and losses would occur, far surpassing the $60 billion estimates for Hurricane Sandy's effects.

New research also shows that climate change may make these storms more likely to occur. You may begin to hear the term "atmospheric river" more often.

The Weather Channel is using it, in quotation marks, in warnings for northern California, as well as the coasts of Oregon and Washington. And some popular media are beginning to adopt the verbiage as well.

Follow Scientific American on Twitter @SciAm and @SciamBlogs. Visit ScientificAmerican.com for the latest in science, health and technology news.

http://news.yahoo.com/mysterious-atmospheric-river-soaks-california-where-megaflood-may-160000315.html

Chriss Christie on climate change

"when you have over 90 percent of the world’s scientists who have studied this stating that climate change is occurring and that humans play a contributing role, it’s time to defer to the experts."
http://nymag.com/daily/intel/2011/09/chris_christie_flaws.html

Third major storm moving into Northern California

By By JOHN S. MARSHALL and TERRY COLLINS | Associated Press – 1 hr 13 mins ago.. .

SAN FRANCISCO (AP) — Another major storm moving into Northern California was expected to bring more pouring rain, flooding and additional problems to an area already soaked after two major storms, forecasters said Saturday.

Residents of Northern California enjoyed just a bit of a respite, but the next storm — the third in a string of powerful weather systems to hit the region since Wednesday — is expected to force several rivers over their banks after it arrives Saturday evening, National Weather Service forecasters said.

With rivers and streams already running high and the ground saturated from the previous storms, the National Weather Service issued flood warnings early Saturday for both the Napa and Russian rivers, two rivers north of San Francisco with a history of flooding, National Weather Service hydrologist Mark Strudley said.

"Some roads will become inundated and some of the agricultural areas will take on some water," Strudley said.

The Napa River was expected to flood near St. Helena and Napa around noon on Sunday, while the Russian River was expected to flood near Guerneville early Monday morning, Strudley said.

The Napa River overwhelmed downtown Napa in 2005, flooding or destroying about 1,000 homes and forcing thousands of residents to leave the area.

With that in mind, residents worked to fill 700 bags with 10 tons of sand Saturday morning, city official Danny Lerma said.

"When you see it happen, you always remember, and you say, 'I'm going to be better prepared,'" Lerma told KGO-TV. "And that's what they're doing right now."

Forecasters also issued flood warnings for the Truckee River near Lake Tahoe and the Susan River in Lassen County, as well as the Eel, Navarro and Van Duzen rivers in far Northern California.

A flash flood watch was also in effect for a wide area of Northern California through Sunday evening.

At the peak of Friday's storm, thousands of people were without power, but by Saturday Pacific Gas & Electric was reporting only scattered outages, spokesman J.D. Guidi said.

The utility had extra crews standing by in anticipation of new outages caused by falling branches and strong winds, Guidi said.

The stormy weather may be behind a crash that involved several cars on Interstate 280 outside of San Francisco on Saturday morning, as well as the death of a Pacific Gas & Electric worker in West Sacramento who was killed after his truck crashed into a traffic signal pole during the stormy weather Friday.

With the ground saturated with water, increasing the possibility of trees and branches falling onto roadways, and the roads expected to be slick, California Highway Patrol officials urged drivers to be extra cautious.

Officials were also warning people to be careful along beaches.

A high surf advisory was issued by the weather service, with swells expected to be 14 to 16 feet along the Northern California coast. In Southern California, high surf was predicted in Los Angeles, Orange and San Diego counties.

In San Diego, the Ocean Beach Municipal Pier was closed because of big waves and high tides.

Elsewhere in the West, a state of emergency was declared in Reno, Sparks and Washoe County in Nevada due to expected flooding as a storm packing heavy rain and strong winds swept through the area.

Reno city spokeswoman Michele Anderson said public servants would be working overtime through the weekend to control what's expected to be the worst flooding there since 2005. The National Weather Service issued a flood warning along the Truckee River.

The weather also prompted cancellations of Christmas parades and tree lightings in Sparks and Truckee, just across the border from California.

Also, a storm rushed through southern Oregon this week, lingering inland over the Rogue Valley and dropping record rainfall. Forecasters said the region should expect more storms over the next few days.
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Third major storm moving into Northern California - Yahoo! News