What Are Hail Streamers?

Threat of Hail

• All thunderstorms carry risks, such as tornadoes, flash floods and lightning strikes. Another risk is the possibility of hail, which carries the threat of damage to cars, homes, crops and people. Although many hailstones are small, they can grow in weight to more than one pound and be similar in size to a softball. For that reason, it is important for people to be aware of when and how hailstorms develop.

Characteristics of Hailstorms

• Typically, hailstorms occur during spring days when warm air mingles with cool air in the upper atmosphere. The combination of these vapors creates large cumulonimbus clouds. These large clouds possess a great deal of energy, which creates updrafts and downdrafts within the cloud. Hail forms when the draft cycle catches supercooled water and develops layers of ice. Hail falls from the cloud when it becomes too heavy for the updraft to support.

Hail Streamers

• Hail streamers result from extremely large hailstones, which may be in excess of three or four inches in diameter. To an observer on the ground, hail streamers look like vertical lines in the cloud. These are really the striations where the heavy hailstones fall through the cloud, breaking up the cloud structure. Occasionally, these striations have a hint of green color.

Distinguishing Hail Streamers

• Streamers can also occur because of heavy rain, but this produces smaller striations referred to as "virga streamers." While virga streamers may not be as dangerous as hail streamers, they are still an indication of heavy thunderstorms. Hail streamers are larger that virga streamers and exist in cumulonimbus clouds during thunderstorms. The large hail indicated by hail streamers is a significant threat to property and personal safety. People who see hail streamers should seek shelter in a safe, covered place as soon as possible.