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Primary reference(s)

WMO, 2018. . Accessed 13 October 2020.

Additional scientific description

The National Oceanic and Atmospheric Administration (NOAA) National Weather Service describes a squall as follows (NOAA, 2019):

• A strong wind characterised by a sudden onset in which the wind speed increases to at least 16 knots and is sustained at 22 knots or more for at least one minute.
• In nautical use, a severe local storm considered as a whole, that is, winds and cloud mass and (if any) precipitation, thunder and lightning.

The American Meteorological Society describes a squall as follows (AMS, 2012):

• A strong wind characterised by a sudden onset, a duration of the order of minutes, and then a sudden decrease in speed. In U.S. observational practice, a squall is reported only if a wind speed of 16 knots or more is sustained for at least two minutes (thereby distinguishing it from a gust).
• In nautical use, a severe local storm considered as a whole, that is, winds and cloud mass and (if any) precipitation, thunder and lightning.

Metrics and numeric limits

Not available.

Examples of drivers, outcomes and risk management

Squalls are sudden changes in wind conditions. In general, a squall may not be very strong and may only last for a short time. However, owing to their unpredictability and sudden arrival, squalls pose a threat to marine operations that require a fairly calm sea state (Lu et al., 2018).

Human health can be severely affected by wind-related hazards such as squalls and windstorms. Direct effects occur during the impact phase of a storm, causing death and injury due to the force of the wind. Becoming airborne, being struck by flying debris or falling trees and road traffic accidents are the main dangers. Indirect effects, occurring during the pre- and post-impact phases of the storm, include falls, lacerations and puncture wounds, and occur when preparing for, or cleaning up after a storm. Power outages are a key issue and can lead to electrocution, fires and burns and carbon monoxide poisoning from gasoline powered electrical generators. In addition, worsening of chronic illnesses due to lack of access to medical care or medication can occur. Other health impacts include infections and insect bites (Goldman et al., 2014).