Lakewatch
El Niño returns--Another wet winter coming?
by Greg Reis
The early signs of El Niño Southern Oscillation are appearing. The National Oceanic and Atmospheric Administration’s Climate Prediction Center is forecasting wetter, cooler weather for the southern half of the United States from November through March. This could mean another wet winter for the Mono Basin!
The El Niño Southern Oscillation—or ENSO—usually occurs every two to seven years. It is characterized by abnormally high sea surface temperatures (SST) in the eastern Pacific Ocean near South America.
There are three types of ENSO events. Type 1 events have the strongest SST anomaly (+2.0 C). There have been 8 type 1 events between 1949 and 1995. Type 2 and 3 events have a weaker SST anomaly (between 0.0 C and +2.0 C), but Type 2 covers a larger area of ocean.
There is no meaningful trend in rainfall data for Type 2 and 3 events, but Type 1 events show a distinct pattern. There is a strong effect in the south, with San Diego having above normal rainfall in eight out of eight Type 1 ENSO years, and a decreased effect in the north, with Eureka having above normal rainfall in only four out of eight years.
The graph below shows that Mono Basin runoff has been above normal in six of the eight Type 1 ENSO years. Five of the top ten runoff years in the Mono Basin have been ENSO years, with four of them Type 1 events. 1995 was an ENSO event, but not Type 1. Since 1950, only the 1982-83 warm episode featured SST anomalies greater than those presently observed. For more information on El Niño on the World Wide Web, see the following:
http://atmos.washington.edu/gcg/RTN/rtnt.html
National Weather Service--San Francisco Bay Area
http://ceres.ca.gov/theme/natrl_env/el_nino.html
So where does Mono Lake stand now? As of August 7, Mono Lake stood at an elevation of 6382.4 feet above sea level. This is a .6 foot rise for the months of June and July, a 2.3 foot rise from the same time last year, and a 7.8 foot rise since the Water Board decision in 1994. The lake will drop a little at the end of the summer due to evaporation, and El Niño will determine what happens from there.
Greg Reis is the Committee’s Information Specialist.
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