White marbles fall from the sky
DECATUR — The afternoon in Northwest Arkansas was full of sunshine and nice temperatures on April 27. In Decatur, it was an average Monday afternoon under the pandemic siege as residents made the best of what they have for now. But on the horizon, a storm was brewing, literally.
As the afternoon wore on, storm clouds began building, Just over the Oklahoma border, west of Decatur, a supercell thunderstorm was gaining momentum as the saucer-like cloud hung on the horizon.
Off to the north, hail shafts streaked the distant horizon. Looking on the Northwest Arkansas radar from the National Weather Service office in Fort Smith at around 5 p.m., the storm gained intensity very quickly and grew into a bigger supercell. As it did, the hail cores began to grow and expand within the system. A few minutes later, the radar indicated the hail cores dissipating. This cycle repeated itself many times in the course of 30 minutes as the storm moved over Decatur and Gentry, dumping heavy rain and frequent cloudto-cloud lightning. The worst was yet to come for persons living east of Decatur and Gentry.
At 6:17 p.m., with dark skies now hanging over Springdale, Bethel Heights and Lowell and a beautiful sunset to the west, the heavens opened up and, at first, small ice pellets began to fall, followed by beautiful round balls of white ice the size of marbles, making contact with cars, houses, the ground and whatever got in its way.
The hailstorm lasted about 10 minutes and covered yards, streets and cars. Then, in a flash, the storm moved into eastern Benton and Washington Counties.
What makes a hailstorm?
Hail is basically water droplets that get caught in a thunderstorm’s updraft and are carried into the cooler reaches of the atmosphere and freeze. If the updraft of the storm is relatively weak, the hail falls as pea-size or smaller. The more powerful the updrafts are in the parent thunderstorm, the more times the ice droplet begins to grow as they collide with another water droplet. There are two types of hailstones. Cloudy ice forms as air bubbles get trapped in newly formed ice. If the water freezes slowly, this gives the air bubbles a chance to escape, forming a clear hailstorm.
When the stones get too heavy for the updrafts to suspend in the atmosphere, they fall as hail.
Often people ask, “why do meteorologists refer to the size of hailstones as pea, marble, teacup, golf ball or softball?” Quite simply, it is easier for the public to relate to the size of everyday objects like marbles and baseballs than one-inch or fourinch hail.
The following is the description size, diameter and typical fall speed of a hailstone:
Pea 1/4 inch Marble 1/2 inch Dime/Penny 3/4 inch 43 mph
Nickel 7/8 inch Quarter 1 inch 50 mph Golf Ball 1 3/4 inch 66 mph
Baseball 2 3/4 inch 85 mph
Grapefruit 4 inch 106 mph
Softball 4 1/2 inch The largest hailstone on record, eight inches and weighing two pounds, fell in Vivian, S.D., on July 23, 2010. To get a perspective on the sheer magnitude of that stone, meteorologists often refer to it as soccer ball or bowling ball size hail. Fortunately, the stone landed in a cornfield where no one was hurt.
A hailstone can cause serious injury or death to a person (although death is relatively uncommon). From 1930 to July 2018, only three people have been killed by a hailstone. These low numbers can be deceiving. Stones of an inch or larger, falling at speeds from 50 to 106 miles an hour, can and in several cases have killed a person if that person chooses to go out into the storm unprotected.
In 1988, the Indian city of Moradabad, in the state of Uttar Pradesh, was hit with orange size hail (around three inches) during a violent thunderstorm which killed 246 people. This storm became one of the deadliest hailstorms to date.
The National Weather Service, Weather Channel and other media outlets recommend the following safety tips during a hailstorm:
Put vehicles under a protected shelter or in a garage.
Bring in pets if possible. Do not park under a highway overpass. The congestion from this could cause serious or fatal accidents.
Seek shelter in a home or buildings.
Stay away from windows, doors, skylights (wind can blow a large hailstone through all of these).
Heed the latest watches and warnings.
A closer inspection of the hailstones revealed a nearly perfect spherical shape on a majority of them. This means that hailstones were tossed and rolled in the updraft long before the storm even reached the Decatur-Gentry-Gravette area. Fortunately, no injuries or serious property damage were reported with this powerful supercell.