Science / Weather Glossary

Freezing Precipitation: Precipitation that is liquid, but freezes upon impact with a solid surface, such as the ground or other exposed surfaces.

Freezing Rain: Rain that falls as liquid and freezes upon impact to form a coating of glaze on the colder ground or other exposed surfaces. It is reported as 'FZRA' in an observation and on the METAR.

Fresh Water: Water found rivers, lakes, and rain, that is distinguished from salt water by its appreciable lack of salinity.

Friction: In meteorology, it is the turbulent resistance of the earth on the atmosphere. Considered as the resistance of fluids (air and water) to the relative motion of a solid body. The amount is de . . . View Full Definition

Friction Layer: The thin layer of atmosphere adjacent to the earth's surface. Surface friction is effective in slowing down wind up to approximately 1,500 to 3,000 feet above the ground. Above this level, a . . . View Full Definition

Front: The transition zone or interface between two air masses of different densities, which usually means different temperatures. For example, the area of convergence between warm, moist air and c . . . View Full Definition

Frontal Passage: It is the passage of a front over a specific point on the surface. It is reflected by the change in dew point and temperature, the shift in wind direction, and the change in atmospheric pres . . . View Full Definition

Frontogenesis: The birth or creation of a front. This occurs when two adjacent air masses exhibiting different densities and temperatures are brought together by prevailing winds, creating a front. It coul . . . View Full Definition

Frontolysis: The destruction or dying of a front where the transition zone is losing its contrasting properties. The opposite of frontogenesis.

Frost: The covering of ice crystals that forms by direct sublimation on exposed surfaces whose temperature is below freezing.

Frozen Precipitation: Precipitation that reaches the ground in a frozen state. Examples include snow, snow pellets, snow grains, ice crystals, ice pellets, and hail.

Fujita-Pearson Scale: A scale that classifies the severity of wind damage intensity based on the degree of destruction as it relates to the wind speed as well as path length and path width of the event. It is nor . . . View Full Definition

Funnel Cloud: A violent, rotating column of air visibly extending from the base of a towering cumulus or cumulonimbus toward the ground, but not in contact with it. It is reported as 'FC' in an observatio . . . View Full Definition

Fusion: The change of state from a solid to a liquid at the same temperature. The heat of fusion is the number of gram calories of heat necessary to change one gram of a substance from the solid to . . . View Full Definition

Gale: On the Beaufort Wind Scale, a wind with speeds from 28 to 55 knots (32 to 63 miles per hour). For marine interests, it can be categorized as a moderate gale (28 to 33 knots), a fresh gale (3 . . . View Full Definition

Gale Warning: A warning for marine interests for impending winds from 28 to 47 knots (32 to 54 miles per hour).

Geophysics: The study of the physics or nature of the Earth and its environment. It deals with the composition and physical phenomena of the earth and its liquid and gaseous envelopes. Areas of studies . . . View Full Definition

Geosphere: Considered the solid portions of the earth, including the hydrosphere and the lithosphere, as opposed to the atmosphere, which lies above it. At their conjunction is the biosphere.

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