One of the surprise products of a hot 
	summer afternoon thunderstorm is the 
	almost magical transformation of the 
	landscape from verdant green to icy 
	white with the onset of a hailstorm. 
	The first sign that hail may be arriving 
	is a growing whitening among the 
	shafts of rain. Soon a rattling sound is 
	heard, as hailstones strike roofs and 
	pavements, and the ground whitens,
	becoming slippery as hailstones cover
	grass and roadways. A hailstorm can be
	the most damaging part of a
	thunderstorm, inflicting injury on a man
	and beast and destroying crops,
	gardens, and property like a giant
	pummeling machine.

	A hailstone is a product of the updrafts
	and down drafts that develop inside the
	cumulonimbus clouds of a thunderstorm,
	where supercooled water droplets exist.
	The transformation of droplets to ice
	requires not only a temperature below
	32F(0C),but also a catalyst in the
	form of tiny particles of solid matter, or
	freezing nuclei. Continued deposits of
	supercooled water cause the ice crystals
	to grow into hailstones.
	What we generally call hailstones have
	passed through several stages of
	accretion, from the first stage, called
	graupel, to small hail, to hailstones.
	Sometimes only the first stage is 
	reached;  at other times hailstones from
	two or more stages may fall to earth
	simultaneously. By scientific
	agreement, an icy conglomeration is
	called a hailstone when it reaches a 
	diameter of 1/5 inch (5 mm). In
	all its forms, hail usually occurs
	in relatively short episodes rather
	than as steady precipitation.

	The major Stages in the development of 
	hailstones can be defined as follows:

	Soft hail, or graupel, consist of white,
	opaque ice [particles, usually nearly
	round (although sometimes conical),
	with a snowlike structure and a 
	diameter up to 1/5 inch (5 mm). Each
	pellet consist of a central ice crystal
	that has accreted supercooled water
	droplets that freeze on the nuclei.
	Graupel is compressible and rebounds
	on a hard surface; thus is sometimes
	called snow pellets.

	Small hail is the same as graupel,
	but differs from its higher density and
	partially glazed surface. Small hail
	particles are generally semitransparent
	and rounded, with conical tips and 
	diameters up to 1/5 inch (5 mm). They
	consist partly of liquid water and
	sometimes have a frozen outer shell.
	Graupel transforms into small hail by
	the liquid water taken in through air
	capillaries in the ice framework.

	Hailstones are concentrations of ice
	arranged in layers, with diameters
	greater than 1/5 inch (5 mm). Stones
	may be as small as peas or as large as
	grapefruits (about 5 inches in
	diameter). Usually they are roughly
	spherical stones, the most common
	form of hailstones, have stratified
	interior structure somewhat resembling
	the rings of an onion: Layers composed
	of clear ice alternate with layers of
	white, granular ice, known as rime,
	formed when the hailstones are carried
	up and down in vertical currents within
	a cloud. Each layer melts a little during
	every descent and aquires a new
	sheathing of ice during each ascent into
	freezing temperatures, creating the
	onionlike layers. When hailstones are 
	tossed out of a chimney-effect updraft
	into a nearby descending current, or
	when the supporting power of an
	updraft weakens, the hailstones descend
	to earth.
	In their travels the stones acquire
	varying textures and appearances. Some
	develop protruding lobes that resemble
	little feet, probably as a result of
	spinning as they fall. Occasionally
	several hailstones freeze together,
	forming irregular chunks of ice that
	smash into pieces on impact with 
	the earth.

Hailshafts and Hailstreaks:

	A hailshaft is a column of hail falling
	from a single thunderstorm cell. The
	ground area swept by the hailshaft is
	known as a hailstreak, typically
	produced by a hail cell (the hailshaft of
	a thunderstorm cell) moving along at
	30-45 miles per hour (about 48-56
	kph), although speeds of 60 miles per
	hour (about 97 kph) have been
	recorded. Hailstreaks normally cover
	areas varying from 100 feet (about 30
	m) to 2 miles (about 3 km) wide and
	about 5 miles (8 km) long. However,
	they have been known to cross several
	counties, covering interstate tracks
	200 miles (about 322 km) long. The
	combination of all the individual
	hailstreaks of a storm are known as
	a hailswath
	An unusually large "super-hailstreak"
	in Illinois in 1968 had a maximum
	width of 19 miles (about 31 km) and a
	length of 51 miles (82 km), covering
	788 square miles (about 2,041 sq km).
	At one moment the area of falling hail
	measured 19 miles (about 31 km) wide
	by 10 miles (about 16 km) long, and
	the hailshaft was moving forward at
	35 miles per hour (about 56 kph). Its
	entire duration was 90 minutes. The
	larger stones were 2 1/4 inches (about
	57 mm) in diameter, and the total
	production was 82 million cubic feet
	(about 2.3 million cu m) of ice.

Hailstorm Facts:

	Following are some interesting facts
	and figures pertaining to hailstorms.

	Weather lore is full of accounts of
	suspiciously large hailstones-some
	have been reported to be the size of an
	elephant, while others are "merely" 20
	feet (6.1 m) in diameter. In the years
	since scientific reporting of weather
	events began, however, the size of
	hailstones seems to have decreased
	considerably. For many years the largest
	hailstone reported and accepted by
	Weather Bureau officials was one that
	fell at Potter, Nebraska, on July 6,
	1928: its circumference was 17.2 inches
	(43.7 cm) and its weight was 1.51
	pounds (685 grams). This record was
	not surpassed until the "new champ"
	fell at Coffeyville, Kansas, on
	September 3,1970. Weighing in at
	1.67 pounds (758 grams), it measured
	17.5 inches (44 cm) in circumference.
	Accounts from other areas of the world
	describe larger and heavier hailstones,
	and from the damage, injuries, and
	even deaths reported, the claims
	seem substantiated.

	A Severe hailstorm on June 3, 1959, at
	Selden, in nortwestern Kansas, left an
	area measuring 9 by 6 miles (14.4 by 
	10 km) covered with hailstones to a
	depth of 18 inches (about 46 cm). The
	hail fell for 85 minutes and did
	$500,000 worth of damage, mainly
	to crops.
	Hailstones tend to be swept downhill
	by accompanying heavy rain, eventually
	accumulating in deep drifts. Piles 6 feet
	(1.8 m) high were reported by Henry
	Wallace, an editor at a farm magazine,
	at Orient, Iowa, on August 6, 1890;
	some of those in protected areas
	remained on the ground unmelted for
	26 days.
	A massive hailstorm in Nodaway
	County, in northwestern Missouri, on
	September 5, 1898, left hail on the
	ground for 52 days, rendering ice-
	clogged fields unworkable for two
	weeks; on October 27, enough hail still
	remained in ravines to be used by local
	residents to make ice cream. On some
	occasions in the Great Plains,
	snowplows have been called out in
	midsummer to clear highways after a
	heavy hailfall.

	The High Plains immediately east of
	the Rocky Mountains experience the
	most frequent hailstorms in North
	America. "Hail Alley" extends
	southeast from northern Alberta,
	Canada, into Montana and continues
	southeast to include the eastern parts of
	Wyoming, Colorado, and New Mexico,
	as well as most of south Dakota,
	Nebraska, Kansas, Oklahoma, and west
	Texas. North America's most hail-
	prone city is Cheyenne; lying to the
	east of the Laramie Range in eastern
	Wyoming, it receives an average
	of 9 to 10 hailstorms per season. Some
	locations in the higher elevations of the
	Rockies may experience 20 or more
	hailstorms annually.
	Hailstorms may occur anywhere in the
	United States if convective activity and
	sufficient moisture are present and if
	the freezing level aloft is relatively low.
	The Pacific Coast has the fewest
	number of hailstorms; activity increases
	considerably in the interior mountains.
	The Arctic and Tropics rarely produce
	hail conditions.

	Seemingly authentic reports of
	hailstorms killing people have come
	from around the world, notably from
	China and India, whose populations are
	very concentrated. In northern India in
	1888, hailstones as large as cricket balls
	(about the size of a baseball) reportedly
	killed 246 persons as well as 1,600
	sheep and goats. Another storm, in 
	western Hunan Province in
	southeastern China, was said to have
	killed 200 people and injured
	thousands in 1932.
	In the United States, eight persons
	were reported by the South Carolina
	Gazette to have been killed by a
	hailstorm along the Wateree River on
	May 8, 1784. Other North American
	reports of deaths from hail came from
	Broome, Quebec, in 1879; Uvalde,
	Texas, in 1909; Windsor, North
	Carolina, in 1931; and near Toronto,
	Ontario, In 1976. Only two deaths
	have been authenticated by the
	National Weather Service (formerly the
	U.S. Weather Bureau). The first
	occurred on May 13, 1939, near
	Lubbock, Texas. A 39-year-old farmer
	died of injuries received when he was
	caught in an open field during a severe
	hailstorm. More recently, an infant
	lying in its mother's arms was killed
	by hail at Fort Collins, Colorado, on
	July 30,1979.

Extraordinary Hailstorm Reports:

	Eyewitness accounts of tremendous
	storms still make for good reading,
	even in this age of video recordings.
	Consider this report of a storm in
	Dubuque,Iowa, on June 16, 1882, in
	the Monthly Weather Review:
	"For thirteen minutes, commencing at
	2:45 p.m., the largest and most
	destructive hailstones fell that were ever
	seen at this place. The hailstones
	measured from one to seventeen inches
	in circumference, the largest weighing
	one pound twelve ounces [794 grams].
	Washington park was literally covered
	with hailstones as large as lemons, and
	large basketballs could be gathered in a
	few minutes. They exhibited diverse
	and peculiar formations, some being
	covered with knobs and icicles half an
	inch in length; others were surrounded
	by rings of different colored ice with
	gravel and blades of grass imbedded in
	them. The foreman of the Novelty Iron
	Works, of this city, states that in two
	large hailstones, melted by him, were
	found small living frogs. A number of
	persons were severely cut and bruised
	by the falling hailstones. The damage
	inflicted is estimated at $5,000 [1882
	dollars]. One florist lost 2,387 panes of
	glass. Hundreds of windows of south
	and west exposure were broken,
	including twenty windows of heavy
	French glass. Railroad men report that
	hail fell at 2 p.m. at McGregor, forty
	miles to the northwest. No hail fell on
	the eastern side of the Mississippi
	[river], or at Julien, six miles west of
	this city."
	Denver has had two very large
	hailstorms in recent times. The first, on
	June 13, 1984, lasted from 1:30 to
	5:30 p.m. Storm Data reported:
	"The worst hailstorm ever experienced
	in the Denver area in terms of damage
	battered the region for several hours.
	The hardest hit cities were the
	northwestern suburbs of Arvada, Wheat
	Ridge, and Lakewood, but large hail
	also fell in Golden, Southeast Denver,
	and Aurora. Damage occurred in all of
	these areas, but by far the worst effects
	of the storm were in the northwestern
	suburbs. Homes and other buildings
	sustained nearly 200 million dollars
	worth of damage. Many thousands of
	cars were battered by giant hailstones,
	and total damage to vehicles was
	estimated at 100 million dollars.
	"In some areas, golfball- to baseball-
	size Hail fell continuously for 30 to 40
	minutes; some spots were pelted with a 
	few stones as large as grapefruits. Roofs
	on thousands of structures were severely
	damaged. Uncounted car windshields
	were broken; two-thirds of Armada's
	police cars were rendered inoperable.
	Torrential rain-as much as 4 3/4 inches
	(121 mm) in Lakewood-combined
	with the hail to clog drains and cause
	widespread damage from flooding. In
	some spots hail was washed into drifts
	several feet deep.
	"About 20 people were injured by
	the giant hailstones; a couple were
	hospitalized. A woman drowned when
	she was trapped under a trailer by
	high water."
	This 1984 storm was surpassed size years
	later by a storm on July 11, 1990 that
	caused $600 million in damage in the
	Denver area.