What the hail

HawaiiNewsNow Video » Tornado not only part of wacky Windward weather

Teresa Vast has lived 40 years in Hawaii, but like many islanders she never experienced a hailstorm.

That was until early Friday morning when hail — some the size of baseballs — fell during a two-hour period in Windward Oahu. The National Weather Service called it record-setting.

"The hail that fell in Kaneohe, as far as I know, was unprecedented," said Tom Birchard, lead forecaster. "We have never had hail of that size at sea level.

"We think we have a new state record as far as hail size at sea level."

Hailstorms occur here on the slopes of the Hawaii island volcanoes, but the hailstones usually melt before reaching sea level, he said.

The weather service has photographs of hailstones that are at least 21⁄2<h$z$> inches in diameter. There is another photograph of a hailstone that is larger, but weather experts aren’t sure whether it is two pieces that froze together, he said.

"They (hailstones) were huge," Vast said.

So much hail fell between 6 and 7:30 a.m. Friday that "at some points it just covered the ground," Birchard said.

Vast has lived near the Mokapu back gate to Marine Corps Base Hawaii for 20 years, and said the blanket of ice on her lawn "looked a bit like snow. … Whole areas of my lawn looked white because it was covered with ice."

Vast, who grew up in Northern California, said she remembers hailstorms there. "But they were more the size of peas." Her husband, Michael Kiran, took pictures of the melting hailstones as he held them, and she sent them to relatives on the mainland.

Vast was thankful that hail did not damage the couple’s solar panels.

Birchard explained that during a thunderstorm there are strong updrafts of warm air and downdrafts of cold air. Water droplets picked up by the updrafts freeze when carried above the freezing level of 32 degrees Fahrenheit.

As the frozen waterdrops fall, they can thaw as they move into warmer air. However, the half-frozen water droplets can get picked up in another updraft and carried back up to the cold air, thus refreezing. With each trip above and below the freezing level, the frozen droplets get bigger until they finally fall as hail.

The weather service received reports Friday morning of a hailstorm that lasted about 30 minutes.

On Tuesday, hailstones — some as large as 1 1⁄2 inches — fell in Wai­ma­nalo, setting a record only to be broken three days later.

Friday’s hail occurred because there were very cold temperatures in the middle and upper portions of the atmosphere, Birchard said, which destabilized the atmosphere, creating very strong updrafts.

"That caused hailstones formed in the thunderstorms to recirculate through the thunderstorm, and that’s the way they grow," he added.