A distinctive atmospheric wave pattern over the Northern Hemisphere may help predict summertime U.S. heat waves more than two weeks in advance, scientists say. Research led by scientists at the National Center for Atmospheric Research in Boulder, Colo., conducted computer simulations of 12,000 years of the movement of the atmosphere over the Northern Hemisphere. During those times when a distinctive pattern dubbed \"wavenumber-5\" emerged, the NCAR scientists said, a major summertime heat wave became more likely to subsequently build over the United States, they reported in the journal Nature Geoscience. \"It may be useful to monitor the atmosphere, looking for this pattern, if we find that it precedes heat waves in a predictable way,\" lead study author Haiyan Teng said in an NCAR release Monday. \"This gives us a potential source to predict heat waves beyond the typical range of weather forecasts.\" The wavenumber-5 pattern -- a sequence of alternating high- and low-pressure systems (five of each) that form a ring circling the northern midlatitudes, can lend itself to slow-moving weather features and raise the chances of stagnant conditions often associated with prolonged heat spells, the researchers said. Heat waves are among the most deadly weather phenomena on Earth. A 2006 heat wave across much of the United States and Canada was blamed for hundreds of deaths, and a prolonged heat wave in Europe in 2003 may have killed more than 50,000 people. Teng said she and her colleagues were conducting ongoing research looking for other circulation patterns that may presage extreme weather events. \"There may be sources of predictability that we are not yet aware of,\" she said. \"This brings us hope that the likelihood of extreme weather events that are damaging to society can be predicted further in advance.\"