Researchers Zhu and Newell at MIT coined the term “atmospheric river” in a 1998 paper which described the phenomenon where moisture laden air from the warm Pacific streams onto the west coast producing heavy rain in California and western Nevada. Current forecasts call for such a storm starting Friday of this week. Where the storm strikes the coast, however, is up in the air – no pun intended.
Beginning February 11 in 1986 a 10 day series of storms hit northern California and Nevada producing rainfall far beyond what would normally be expected for the month and even many entire winters. The ARkStorm@Tahoe Project labels this huge storm as an “historic atmospheric river”. I remember this storm pretty well (with apologies to the local meteorologist, Mike Alger, who warns us against relying on our own experiences when it comes to weather). My rain gauge for that series of storms recorded over 10 inches of rain over the 10 day period at my house in northwest Reno (with most rain coming toward the end of the storm). The dry dams on Peavine filled and water cascaded down northwest Reno streets. Flood waters from Evans Creek blocked north Sierra Street and ran through the University and beyond. If it wasn’t an atmospheric river, it was, at least, a very wet and relatively warm series of storms that produced wide-spread flooding in Reno as well as throughout northern California. NOAA has written about this storm (here) and you can even watch loops of satellite images of the storm over the 10 days (here).
February 1969 also produced a reversal of relatively dry winter conditions into a remarkably wet one with record snow depths at Lake Tahoe, record cold in Reno, and the filling of dry Tulare Lake in California’s Central Valley. I was a volunteer Ski Patrolman at Slide Mountain (now Mt Rose Ski Resort) on weekends at the time, and we were sent up to help resort personnel dig out the central chairlift which was buried by a several day snowfall. In addition to the remarkable storm in February 1986, February 1969 produced a huge precipitation month in the Sierra and western Nevada as well as in northern California. The Tahoe Tribune 2009 story, “1969 | Tahoes record-setting winter”, celebrated the 40th anniversary of that memorable winter. And 1969 is memorable for more than humans. Biologists G. Gary Scoppettone and Mark Coleman wrote in their 1983 paper “Life History and Status of the Endangered Cui-ui of Pyramid Lake, Nevada”, that 92% of the Cui-ui fish in Pyramid Lake 14 years later were from the fish that were able to reproduce in that exceptional water year of 1969.
January 1997 saw one of the largest floods on the Truckee River every recorded. It also occurred at a time when Lake Tahoe was already relatively full so the river at its source contributed significant flows downstream. The 1997 storm also qualifies as an “atmospheric river” type storm according to the ARkStorm@Tahoe Project website. The USGS report describing the historic flood sums it up nicely:
“In late December 1996, storms built up a large snowpack (more than 180 percent of normal) in the higher altitudes of the Sierra Nevada in the Truckee River Basin, Western Nevada and covered the valleys along the eastern Sierra Nevada front as well. Then, a subtropical storm system originating in the central Pacific Ocean near the Hawaiian Islands brought heavy, unseasonably warm rain to the Sierra Nevada from December 30, 1996 through January 3. 1997.”
The snowpack below 7,000 feet mostly melted away and 27.7″ of rain were recorded at Squaw Valley at 8,200 feet elevation. The results were massive flooding in the Truckee Meadows and sending large flows of water down the Truckee River into Pyramid Lake. Likewise, the Carson and Walker Rivers in western Nevada also experienced large floods with water inundating Minden and Gardnerville on the Carson River and Yerington on the Walker River. The future drought that kicked in in 2000 was not foreseen and the community focused instead on flood control. (The flood was followed by an expensive dredging project throughout the Truckee Meadows that damaged the river environment and produced no lasting benefits to reduce flooding.)
So, as the “atmospheric river” heads to northern California and, hopefully, Nevada this February 2015, we can all hope that it comes close to the Tahoe area. I don’t say that to hope for a damaging flood, although that might occur, it is because large storms are really the life-blood of the Truckee River and the Tahoe-Truckee-Pyramid system of Lake-river-Lake. We can’t escape our need for these large storms for all the good that they do for us and for the ecosystem that depends on them.