Definitions Weather (METAR, TAF...)

AIREP

An AIREP is a report sent from an aircraft to a ground station. It may contain the aircraft’s position, flight level, fuel information and weather observed during the flight.

ATIS

Pilots use ATIS to receive current routine information about an airport before arrival or departure. It normally includes weather, runway and approach information and helps reduce radio frequency congestion.

METAR

A METAR gives the actual observed weather conditions at an aerodrome at a specific time. It includes information such as wind, visibility, clouds, temperature and pressure.

TAF

This is a forecast of the weather expected at an aerodrome during a specified period. It helps crews plan the flight and anticipate possible changes in weather conditions.

VOLMET

VOLMET provides meteorological information to aircraft in flight by radio broadcast or data link. It can include current aerodrome weather reports, forecasts and SIGMET information.

SIGMET

A SIGMET is issued when significant en-route weather exists or is expected and may affect flight safety. It warns crews about hazards such as severe turbulence, severe icing, thunderstorms or volcanic ash.

Clear-air turbulence (CAT)

Clear-air turbulence occurs mainly at higher altitudes without visible clouds or an obvious warning. It is dangerous because sudden changes in altitude or attitude can injure occupants and make aircraft control more difficult.

Microburst

A microburst is a small but very intense downdraft that spreads outward when it reaches the ground. The rapid changes in wind can cause a sudden loss of airspeed and lift, especially during takeoff or landing.

Windshear

Windshear means a rapid change in wind speed or direction over a short distance. At low altitude it can quickly change the aircraft’s airspeed and lift and may lead to loss of control.

Thunderstorm

A thunderstorm can combine several serious hazards at the same time, including heavy rain, lightning, hail, severe turbulence, icing and windshear. For this reason, pilots normally avoid flying through thunderstorms.

Turbulence

Turbulence is irregular and disturbed movement of air. Strong turbulence may cause abrupt changes in altitude, attitude or airspeed and can result in injuries or structural damage.

Ruts and ridges

Ruts and ridges are uneven depressions and raised areas on a runway surface or in runway contamination. They can affect braking and directional control and increase the risk of a runway excursion.

Hail

Hail consists of pieces of ice produced by strong convective clouds. It can damage the windshield, radome, wings and engines, and hail ingestion may also cause serious engine problems.

Fog

Fog is made up of tiny water droplets close to the ground and can reduce visibility severely. Poor visibility makes taxiing, takeoff, approach and landing more difficult and increases the risk of navigation or runway errors.

Haze

Haze is caused mainly by very small dry particles suspended in the air. Although it may look less serious than fog, it reduces visibility and visual contrast and can make terrain or runway features harder to see.

Mist

Mist consists of small water droplets suspended near the surface and normally reduces visibility less than fog. It can still make visual references difficult, particularly during approach, landing and taxiing.

Icing

Icing occurs when ice builds up on parts of the aircraft. It can disturb the airflow over the wings, increase drag, reduce lift and affect engines, instruments and flight controls.

Slush

Slush is a mixture of water and partly melted snow on the runway. It can reduce braking effectiveness, increase rolling resistance and create spray or ingestion problems during takeoff and landing.

Volcanic eruption

A volcanic eruption may release large amounts of ash and gases into the atmosphere. Volcanic ash can damage engines, erode windscreens, contaminate systems and, in severe cases, cause engine flameout.

Sandstorm

During a sandstorm, strong winds carry large quantities of sand and dust through the air. The main risks are very poor visibility, abrasion of aircraft surfaces and possible sand ingestion into the engines.

Snowstorm

A snowstorm brings heavy snowfall and may also include strong winds. It can reduce visibility, contaminate runways, reduce braking action and create icing problems on the aircraft.