Downdraft

A downdraft is a downward movement of air in the atmosphere, particularly within a thunderstorm or weather system. It is the opposite of an updraft, which is an upward movement of air. Downdrafts can significantly impact weather patterns and are a critical component in the development of severe weather such as thunderstorms, tornadoes, and microbursts.

Characteristics

Downdrafts occur when cool, dense air descends rapidly due to gravitational pull. This can happen for several reasons, including cooling of air by evaporation, pressure differences, and the drag of precipitation. Downdrafts can vary in scale from small and localized to large and extensive, affecting large areas and multiple weather systems.

Types of Downdrafts

There are several types of downdrafts, each with unique characteristics and implications:

Macroburst

A macroburst is a large downdraft with an outflow diameter of 2.5 miles (4 km) or more and lasting for at least 5 minutes. Macrobursts can cause extensive damage due to the high winds they produce, similar to damage from strong tornadoes.

Microburst

A microburst is a smaller-scale downdraft that can occur within thunderstorms. It has an outflow area of less than 2.5 miles (4 km) across and can last for a couple of minutes. Microbursts can be particularly dangerous to aircraft during takeoff or landing phases.

Heat Burst

A heat burst is a rare atmospheric phenomenon characterized by a sudden increase in temperature and decrease in humidity, accompanied by strong winds spreading out from a thunderstorm as it collapses.

Impact on Weather and Environment

Downdrafts play a significant role in severe weather development. They are responsible for gust fronts that can precede thunderstorms, cooling the air and potentially triggering additional storms. In aviation, downdrafts pose a hazard, particularly during the landing or takeoff stages of flight.

Detection and Study

Meteorologists use tools such as Doppler radar and satellite imagery to detect and study downdrafts. Understanding these phenomena helps improve weather forecasting and warning systems, potentially saving lives and reducing property damage from severe weather events.

See Also

• Wind shear
• Convective storm detection
• Atmospheric pressure
• Weather forecasting