Will it be a Good Ski Season? Correlation between El Nino and Snowfall


This study investigates the correlation between El Niño and the weather across the U.S. El Niño is defined as warmer waters in the equatorial Pacific. La Niña is colder waters in that same area. The correlation between El Niño index and weather station data from 25 U.S. cities was computed for three variables: precipitation, snowfall and temperature. Daily weather data was averaged by month and year. It was found that El Niño correlates differently for different regions of the U.S. From New Mexico to the east coast, the weather is colder and wetter during El Niño and warmer and drier during La Niña (statistically significant and highly significant correlations). The whole southern half of the U.S. is wetter during an El Niño. The north-western U.S. is warmer, and areas near Ohio are drier. However, the correlation is not immediate. The data shows about a five month time lag between El Niño and the wintertime snowfall. The previous August El Niño index is the best predictor of total winter snowfall for most U.S. cities. El Niño is a good predictor of seasonal weather, but not perfect. The difference between strong El Niño and strong La Niña snowfall in Los Alamos, New Mexico, is 30 in. on average, while the standard deviation of the error of the best fit line is 27 in. This means that the prediction is almost as large as the variability.