Weather Outlook: 2013 Drought?

Careful analysis of the historical record indicates that recent precipitation levels and current soil moisture conditions provide little guidance in forming expectations for precipitation levels next summer. Historically, odds of favorable or unfavorable growing conditions have been independent of precipitation levels in the last half of the previous year. Beyond this particular analysis, we would expect to find general independence of year-to-year weather conditions.

The drought of 2012 in the Midwest was a continuation of a weather anomaly that began in 2010. The historical indicator of El Niño and La Niña is the Southern Oscillation Index (SOI). The index is based on the 90-day standardized deviation of atmospheric pressure between Tahiti and Darwin, Australia. The standardized difference reached 0.8 on July 22, 2010, signifying the beginning of a La Niña event (Figure 1). By Oct. 23, 2010, the event was clearly the second strongest event in the 100+ years of record keeping. The young but potent La Niña resulted in an abrupt change in weather on a planetary basis that included record flooding in Montana, North Dakota and adjacent Canada, and enormous amounts of water to drain into the Missouri river during 2011.