How Hailstones Form

• Hail is a product of cumulonimbus storm clouds. These clouds create powerful updrafts of warm air and downdrafts of cold air. Water droplets rise within the updrafts, freezing as they rise above the freeze line. The frozen droplets then enter the downdraft, partially thawing. If caught up in a circulation between the two, the hailstones will continue to refreeze and partially thaw, acquiring a new layer of ice with each refreeze. Ultimately, they become too heavy for the updraft to support, and fall to the ground as hailstones.
  
  

Hail Intensity Scale

• The Tornado and Storm Research Organization (TORRO) has developed an international scale, much like the Saffir-Simpson hurricane wind scale, to estimate the destructive potential of hail based upon size. This hail scale is broken down into 11 levels, spanning from H0 to H10. H0-sized hail represents hard hail. H4-sized represents severe hail, with the potential to shatter most glass and damage vehicles. H6-sized hail represents destructive hail, capable of pitting brick and masonry walls. H9-sized hail represents a super hailstorm, with the potential for extensive structural damage.
  
  

Hailstone Size Descriptions

• The sizes of hailstones are often referred to in relation to common items. These sizes range from 1/4-inch hail stones that may be referred to as "pea-sized" to hailstones as large as 4 1/2 inches in diameter or "softball-sized." Ping pong ball-sized hail is the most common size for producing damage, while pea-sized hail is the most common size of hail produced.
  
  

Hailstone Records

• The largest hailstone on record fell on June 23, 2003, in Aurora, Nebraska. This hailstone had a diameter of 7 inches and a circumference of 18.75 inches. The heaviest hailstone on record fell on Sept. 3, 1970, in Coffeyville, Kansas. This hailstone weighed 1.67 lbs., with a diameter of 5.7 inches and circumference of 17.5 inches. Two hailstorms tie for the costliest hailstorms on record. The first occurred on May 5, 1995, in Fort Worth, Texas. The second occurred on April 10, 2001, in Kansas City. Both hailstorms were responsible for an estimated $2 billion in damages.
  
  

Hailstone Detection

• Meteorologists use radar to look inside storm clouds to locate the presence of potentially dangerous hail. The hailstones reflect more energy than raindrops, appearing as red shades on the radar. The WSR-88D Doppler radar can even estimate the size of the hail, based upon the intensity of the return. Hail provides an indication that a storm has both up and downdrafts, indicating the potential for tornado development. However, storms can produce hail without tornadoes and tornadoes without hail.