Hail melts more before hitting


Heat wafting upward from the earth is raising the layer in the air where temperatures are warm enough to melt hail, scientists at the National Center for Atmospheric Research have found.

This leads to increased shrinking of big hailstones that otherwise could shatter car windows, batter roofs and wreak havoc on food crops.

At the same time, higher temperatures as the climate warm jacks up moisture in the turbulent upper-elevation clouds where hail forms — favoring bigger hail.

The net impact is a wild card. And NCAR scientists say they’ve proposed the nation’s largest hail research project in 40 years to figure out likely future impacts. Climate warming locked in for at least two more decades, depending on whether people reduce air pollution, is creating conditions that scientists say will favor intense storms of one form or another.

And hail damage bills are ballooning, particularly around Denver and Dallas, located in what have been hotbeds for hail.

Even last year when hail storms lagged below average, insurers nationwide saw a relatively high total of $16 billion in claims for damage, said Ian Giammanco, senior director of data analysis and research meteorologist for the Insurance Institute for Business and Home Safety. He joined Colorado-based atmospheric scientists at a recent hail conference at NCAR facilities in Boulder – shortly before hurricanes began hammering the southeastern coast.

“The biggest driver of the rising costs really is the expansion of the built environment. Areas around Dallas-Fort Worth and east of Denver that used to be farmland 30 to 40 years ago are now dense suburban neighborhoods. Also, compounding the problem, we are building larger homes and putting more on the same footprint of land,” Giammanco told the Denver Post.

“We just have more things in harm’s way.”

Climate warming could cut either way with hail.

Over the past 40 years, the atmospheric layer where hail melts has risen by about 500 feet, NCAR senior scientist Andrew Heymsfield said in an interview.

That’s the result of global warming, Heymsfield said. “When the surface temperatures are increasing, the height of the melting layer increases.”

Yet, at the same time, “the air holds measurably more moisture” as the temperatures rise, he said.

This means that, in the turbulent high-elevation clouds where hail forms in rising and falling air currents, “water vapor in the air is increasing, and that will increase the rate at which hail grows.”

These conditions could create monster hailstones – before the hail begins falling from the sky.

“But counteracting that is the increased melting,” Heymsfield said. “It is unclear, at this point, what the net effect is. … The damage may not be any more severe due to the melting.”

Hence the push for research that could help anticipate impacts and improve forecasts. The last major government-backed hail studies were done in the 1980s, scientists said.

Since then, NCAR teams have proposed projects that would have deployed an armored A-10 warplane to penetrate super-intense storms and take measurements — useful for understanding how hail forms. National Science Foundation officials deemed this approach too costly.

Back then, scientists widely understood hail as round. They now see hail as oblate, shaped more like mini footballs than baseballs.

The latest proposed project would deploy aircraft upwind of storms but these would not attempt to penetrate the core area where convection creates hail, Heymsfield said. Instead, researchers would rely on radar and launch drones carrying sensors that could take measurements inside storm cells. Researchers also may release tiny metal particles that could mimic hail stones and be traced, he said. The project, if approved, would begin in 2024.

Ground-level collection of hail stones plays a role. “Don’t just put those large hailstones into a margarita,” Giammanco said at the conference in Boulder, proposing use of 800-number phone systems and phone apps for gathering data across vast rural areas when hail hits.

The rising damage costs as storms intensify compel better research, and NCAR officials said hail is a problem that cannot be ignored. A record-setting hail storm in Denver on May 8, 2017, led to $2.3 billion in claims. Insurance officials anticipated that, soon, a single hailstorm will lead to damages exceeding $3 billion.

Golf ball and larger sized hail ...
Golf ball and larger-sized hail stones fell in Edgewater, Colorado, causing damage to cars, homes and businesses on May 8, 2017. (Photo by Seth McConnell, Denver Post file)


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