Deadly summer heat waves in the eastern United States may be predictable nearly two months before they occur, giving emergency planners and farmers more time to prepare, scientists reported on Monday.
The key to such an advance forecast, scientists said, is the occurrence of a distinctive pattern of water temperatures across a wide stretch of the North Pacific Ocean. While the existence of the pattern does not guarantee that a heat wave will occur, it significantly increases the odds of one happening as much as 50 days later.
From 1999 to 2010, about 620 people died each year, on average, from heat-related illness in the United States, according to the Centers for Disease Control and Prevention. Some heat waves have been especially lethal, like the one in Chicago in 1995 when more than 700 people, most of them old or infirm, died over five days.
Given more lead time, emergency planners could take measures like establishing more cooling centers at schools and other buildings, and stepping up programs to track homeless people and homebound, chronically ill older Americans. Farmers could arrange for more irrigation for crops and extra water and shade for livestock.
In a study published on Monday in the journal Nature Geoscience, the researchers first identified extremely hot summer days in the eastern half of the country from 1982 to 2015. Then they looked at temperature data for sea surfaces — specifically, the extent to which temperatures were above or below normal — for the same period.
“The pattern popped out at us really clearly,” said Karen A. McKinnon, a postdoctoral researcher at the National Center for Atmospheric Research, in Boulder, Colo., and the lead author of the study. Not only did it exist on those hot days — defined as about 12 degrees hotter than normal summer temperatures — “but importantly, up to seven weeks before,” Dr. McKinnon said.
Randall Dole, a senior scientist at the National Oceanic and Atmospheric Administration who has studied heat-wave predictability but was not involved in the study, said the results provided “a tantalizing hint for more long-lead predictability of some extreme weather events than we might otherwise have anticipated.”
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SOURCE: NY Times, Henry Fountain