At 4.25 inches long, 2.25 inches tall and 2 inches wide, a hailstone that fell on the windward side of Oahu this month has been declared the largest on record to hit Hawaii, the National Weather Service announced. Records for Hawaii go back to 1950 and the previous record was a relatively puny 1 inch in diameter.
"The record-setting hailstone was dropped by a supercell thunderstorm on the windward side of Oahu and produced large hail in Kaneohe and Kailua," the service said in a statement. "Numerous reports of hail with diameters of 2 to 3 inches and greater were reported. Hail to the size of golf balls and baseballs can only form within intense, thunderstorms called 'supercells'," the service added. "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 did occur on March 9. Conditions were ideal for a supercell to form, which on National Weather Service radar imagery looked exactly like such storms in the central portions of the contiguous United States where severe hail larger than an inch in diameter is most common." The March 9 supercell also spawned a tornado with winds of 60-70 mph in Lanikai and Enchanted Lakes on Oahu. A hailstone that hit Vivian, S.D., on July 23, 2010, holds the U.S record for largest diameter (8 inches) and for weight (1.938 pounds). A hailstone in Aurora, Neb., on June 22, 2003, has the largest circumference (18.75 inches). - MSNBC.