Hailstone sets state record for Hawaii

Dropped by ‘supercell’ over Oahu


Hail measured by a ruler
Record-setting hailstone from the Hawaii 'supercell' thunderstorm that hit the Hawaiian island of Oahu on March 9, 2012.

Download image (Credit: NOAA)

A hailstone with the diameter of roughly that of a grapefruit that hit Oahu on March 9, 2012, has been confirmed as the largest hailstone on record for the state of Hawaii.

“The final measurement of the hailstone was 4 1/4 inches long, 2 1/4 inches tall, and 2 inches wide,” said Michael Cantin, warning coordination meteorologist at NOAA’s National Weather Service in Honolulu, which, along with NOAA's State Climate Extremes Committee, confirmed the new state record. “According to hail report records for Hawaii kept back to 1950 the previous state record hailstone was 1 inch in diameter.”

The record-setting hailstone was dropped by a “supercell” thunderstorm on the windward side of Oahu that also produced large hail in Kaneohe and Kailua. Numerous reports of hail with diameters of 2 to 3 inches and greater were reported. The National Weather Service investigated a hailstone reportedly larger than 3 inches in diameter, which was collected by a resident in the Aikahi neighborhood of Kailua. Upon inspection, it was apparent the stone was much larger.

Stone size matters

Hail the size of a penny (diameter of 3/4 inch) or quarter (diameter of one inch) has been reported in Hawaii only eight times since records began, and there is no record of hail larger than 1 inch in diameter. Why? Because conditions required to form hail larger than an inch are extremely rare in Hawaii. 

Hail the size of golf balls and baseballs can only form within intense thunderstorms called supercells. These supercells need warm, moist air to rise into progressively colder, drier air, as well as winds changing direction and increasing speed with increasing height off the ground. For both sets of conditions to exist at the same time in Hawaii is extremely rare, but that did occur on March 9. Conditions that day were ideal for a supercell to form — which on National Weather Service radar imagery looked very much like that from such storms in the central portions of the contiguous United States where severe hail larger than 1 inch in diameter is most common.

Supercells can also produce tornadoes, another rarity in Hawaii.  The same hail-producing supercell produced a confirmed EF-0 tornado with winds of 60-70 mph in Lanikai and Enchanted Lakes on Oahu.

Other ‘heavy hitters’

A hailstone that hit Vivian, S.D., on July 23, 2010, holds the U.S. record for the largest diameter (8 inches) and heaviest weight (1.938 pounds). One that landed in Aurora, Neb., on June 22, 2003, set the nation’s record for the largest circumference (18.75 inches).

Posted Mar. 23, 2012 NOAA logo.