What Causes High & Low Precipitation?

Moisture

• The moisture content in any given area where a supercell forms can cause it to be any of the three types. In weather conditions, moisture content is the amount of water in the air, usually in vapor form. When a supercell forms, it gathers most of the moisture content from its surroundings. Threats from supercells include heavy rains, destructive hailstorms, and a very strong updraft. Depending on the moisture it gathers, it can either be a low precipitation or high precipitation thunderstorm.

Precipitation

• Understanding the basic definition of precipitation in relation to weather will give more specific information on how high and low precipitation forms. Precipitation can be liquid or solid; hail, snow, rain and sleet are different forms of precipitation. These form when warm air meets cold air in the atmosphere. Warm air tends to rise from the surface and cold air attracts to the surface; their meeting point causes precipitation if the atmosphere has enough moisture content.

Weather Conditions Causing High Precipitation

• High precipitation (HP) supercells usually form in the East Plains of the US and in some parts of Quebec and Ontario in Canada. These areas tend to have a high amount of moisture content in the atmosphere. They contain a huge amount of water that usually comes in the form of small hail and heavy rain. The strong winds can form large tornadoes that have the ability to devastate anything along their path. HP cells are the largest type of supercell.

Weather Conditions Causing Low Precipitation

• Low precipitation (LP) supercells are also labeled by meteorologists as "dryline thunderstorms" and usually occur along the west side of Texas and the Great Plains region, where the dryline is located. The dryline is the confluence zone in which the air coming from the Gulf of Mexico, which has a lot of moisture content, meets the dry air that comes from the west deserts of the Great Plains. When these two meet, they create a weather disturbance that can cause LP supercells to form.

  Low precipitation supercells tend to be smaller than high precipitation supercells, but they are still capable of damaging anything that comes across their path. Sometimes they come with little rainfall, but the hail produced can be large enough to be dangerous to humans. LP supercells also generate tornadoes.