A gale is a strong, sustained wind event defined by its intensity and duration. It represents a significant increase in atmospheric movement capable of causing hazards on both land and sea. Understanding the specific wind speeds and resulting effects is important for safety, especially in coastal areas and for mariners.
How Gales are Classified
The standard tool for classifying wind strength globally is the Beaufort Wind Scale. On this scale, a gale spans a range of forces, typically beginning at Force 7, often termed a “Near Gale,” and extending through Force 10, which is sometimes called a “Whole Gale.”
A Force 8 gale, sometimes called a Fresh Gale, corresponds to a sustained wind speed between 34 and 40 knots, or approximately 39 to 46 miles per hour. A Strong Gale, or Force 9, represents a sustained speed of 41 to 47 knots, which is 47 to 54 miles per hour. The wind speed thresholds are precise, ensuring that a “gale warning” issued by a weather service refers to a specific, measurable threat level.
Observable Characteristics and Effects
The physical consequences of a gale differ significantly between open water and land environments. At sea, a Force 8 gale creates moderately high waves, where the edges of the crests begin to break into spindrift. The foam generated by these breaking waves is then blown in well-marked streaks along the direction of the wind.
As the wind strengthens to a Force 9, the sea state becomes more severe, with high waves reaching approximately 6 meters in height. The large amount of dense foam and spray reduces visibility, making navigation extremely difficult and dangerous for most vessels. On land, a Force 8 wind makes walking against it very difficult, and small branches and twigs are actively broken from trees. A Strong Gale (Force 9) can begin to cause slight structural damage, such as blowing shingles or slates off roofs.
Differentiating Gales from Other Wind Events
A gale is specifically defined by its sustained intensity, which distinguishes it from both weaker and stronger wind phenomena. A “storm” on the Beaufort scale is the next step up from a gale, typically classified as Force 10 or 11, with wind speeds starting at 48 knots. These events include the uprooting of trees and considerable damage to structures.
The term also differs from a “squall,” which is characterized by a sudden, sharp increase in wind speed that lasts for only a few minutes, rather than being a sustained wind event. While a squall may briefly reach gale-force speeds, its short duration is its defining characteristic, often associated with passing features like thunderstorms. The most powerful wind events, such as a hurricane or cyclone, are classified at the very top of the scale as Force 12, with sustained speeds of 64 knots or greater, representing the highest level of destructive force.