Although the deadly heatwaves that afflict the United States arise from chaotic forces, they could be predicted up to three weeks before they hit.

As yet, heatwaves cannot be foreseen until about ten days in advance. However, in a 12,000-year computer simulation of general atmospheric circulation, Haiyan Teng at the National Center for Atmospheric Research in Boulder, Colorado, and her colleagues observed patterns in the meanderings of high-altitude winds that tended to precede North American heatwaves by 15–20 days.

In the model, large-scale circulation anomalies that increased the risk of heatwaves were not linked to other commonly used indicators, such as monsoons or sea surface temperatures. Monitoring mid-latitude atmospheric dynamics could allow more accurate and longer-term forecasts, the authors say.

Nature Geosci. http://doi.org/pnt (2013)