Yellowstone floods reveal forecasting flaws in warming world
BILLINGS, MONT. » The Yellowstone National Park area’s weather forecast the morning of June 12 seemed fairly tame: warmer temperatures and rain showers would accelerate mountain snow melt and could produce “minor flooding.” A National Weather Service bulletin recommended moving livestock from lowlying areas but made no mention of danger to people.
By nightfall, after several inches of rain fell on a deep spring snowpack, there were record-shattering floods.
Torrents of water poured off the mountains. Swollen rivers carrying boulders and trees smashed through Montana towns over the next several days. The flooding swept away houses, wiped out bridges and forced the evacuation of more than 10,000 tourists, park employees and residents near the park.
As a cleanup expected to last months grinds on, climate experts and meteorologists say the gap between the destruction and what was forecast underscores a troublesome aspect of climate change: models used to predict storm impacts do not always keep up with increasingly devastating rainstorms, hurricanes, heat waves and other events.
“Those rivers had never reached those levels. We literally were flying blind not even knowing what the impacts would be,” said Arin Peters, a senior hydrologist with the National Weather Service.
Hydrologic models used to predict flooding are based on long-term, historical records. But they do not reflect changes to the climate that emerged over the past decade, said meteorologist and Weather Underground founder Jeff Masters.
“Those models are going to be inadequate to deal with a new climate,” Masters said.
Another extreme weather event where the models came up short was Hurricane Ida, which slammed Louisiana last summer and then stalled over the Eastern Seaboard — deluging parts of Pennsylvania, New Jersey and New York with unprecedented rainfall that caused massive flooding.
The weather service had warned of a “serious situation” that could turn “catastrophic,” but the predicted of 3 to 6 inches of rain for New York, New Jersey and Pennsylvania was far short of the 9 to 10 inches that fell.
The deadly June 2021 heat wave that scorched the Pacific Northwest offered another example. Warmer weather had been expected, but not temperatures of up to 116 degrees that toppled previous records and killed an estimated 600 or more people in Oregon, Washington state and western Canada.
The surprise Yellowstone floods prompted a nighttime scramble to close off roads and bridges getting swept away by the water, plus rushed evacuations that missed some people. No one died, somewhat miraculously, as more than 400 homes were damaged or destroyed.