CAA NZ CPL Meteorology key terms

A coded forecast of expected weather conditions at an aerodrome for a stated period, issued at scheduled times and used by pilots for flight planning before departure and en route.

A coded routine observation of actual weather at an aerodrome, issued at fixed intervals (commonly hourly or half-hourly) and used to confirm conditions before takeoff or landing.

A coded aerodrome observation issued outside the routine schedule when conditions change significantly, such as visibility, cloud, or wind crossing specified threshold criteria.

A short statement appended to a METAR or SPECI giving expected conditions at that aerodrome over the next few hours, using change indicators such as BECMG or TEMPO.

A change indicator in coded forecasts meaning a gradual, permanent change to new conditions within a stated time window, as opposed to a temporary fluctuation.

A change indicator in coded forecasts meaning temporary fluctuations that may last for periods shorter than one hour, each lasting less than half the stated window.

A corrected or reissued forecast replacing an earlier TAF because the original no longer reflects expected conditions, marked as amended so users know to disregard the previous version.

A three-letter indicator in coded forecasts or observations showing the report has been amended to correct or update information; it warns users that an earlier version exists.

A three-letter indicator in coded reports showing the message has been corrected for an error such as a wrong time group, figure, or omitted element.

A coded contraction meaning visibility is 10 km or more, no cloud below 5000 ft or below the highest minimum sector altitude, no cumulonimbus or towering cumulus, and no significant weather.

A coded abbreviation meaning no significant weather, used in forecasts and trend statements to indicate that no weather phenomena of operational significance are expected.

The part of a coded observation or forecast giving cloud amount, height of base in hundreds of feet above aerodrome level, and cloud type where significant, such as FEW, SCT, BKN, OVC.

The height above ground or aerodrome level of the lowest broken or overcast cloud layer, or of the vertical visibility into obscuration, whichever is lower.

A cloud amount descriptor meaning broken, covering five to seven oktas of the sky; when it is the lowest layer it defines the ceiling for operational purposes.

A cloud amount descriptor meaning overcast, covering eight oktas of sky, indicating a complete cloud cover and, when lowest, setting the ceiling.

The height to which an observer can see vertically into an obscuration such as fog or heavy snow when the sky is hidden, coded as VV followed by hundreds of feet.

The coded element in observations and forecasts giving prevailing visibility in metres, sometimes with a minimum value and direction when visibility varies significantly across the aerodrome.

Runway visual range: an instrument-derived estimate of the distance a pilot can see along a runway, reported in metres and used when visibility is low or conditions are marginal.

The coded element describing present or expected weather using two-letter descriptors and precipitation codes, such as RA for rain, SH for showers, or TS for thunderstorm.

The coded element giving direction in degrees true and speed in knots, with gusts after the letter G; a leading VRB indicates variable direction and 00000 indicates calm.

A brief peak in wind speed significantly above the mean, coded after G in reports; pilots must allow for it on approach, takeoff, and taxi.

A coded indication that wind direction is fluctuating, shown as VRB when speed is low or as two extreme directions when the variation exceeds 60 degrees.

The altimeter setting that, when set on the subscale at aerodrome level, makes the altimeter read aerodrome elevation; used for terrain clearance and approach.

The altimeter setting that makes the altimeter read height above a specified reference such as aerodrome level, rather than elevation above mean sea level.

The standard pressure setting of 1013.2 hPa used above the transition altitude so all aircraft share a common reference for flight levels.

The coded element in observations giving pressure in hectopascals, usually QNH, sometimes with QFE or the sea-level pressure in trend reports.

A surface of constant pressure shown on the altimeter when set to standard pressure, expressed in hundreds of feet and used above the transition altitude.

The altitude at or below which aircraft use QNH and above which they use standard pressure and flight levels; it is published for each aerodrome or area.

A coded warning of significant en-route weather such as severe turbulence, severe icing, volcanic ash, or tropical cyclone, issued for a specified information area and valid period.

A coded advisory of less severe en-route weather than a SIGMET, covering phenomena such as moderate turbulence, moderate icing, or widespread low cloud and visibility.

A pilot report of actual conditions encountered in flight, such as turbulence, icing, or wind shear, which supplements instrumented observations and can prompt warnings.

A routine or special report transmitted by an aircraft in flight giving position, time, flight level, and meteorological conditions encountered, feeding into forecasting and warnings.

A specialised message giving the observed and forecast position and movement of volcanic ash clouds, issued because ash poses a severe hazard to aircraft engines and windscreens.

Aerodrome procedures activated when visibility or cloud base falls below set values, affecting runway use, approach minima, and surface movement; RVR reports become critical.

A chart depicting forecast en-route hazards such as fronts, turbulence, icing, and cloud for a stated validity time, used for pre-flight planning and route selection.

The common abbreviation for a significant weather chart, showing areas of hazardous weather and their expected movement over a defined validity period.

A forecast chart for a selected flight level showing wind direction and speed and temperature, used to plan routes, fuel, and cruise levels.

The stated start and end times of a forecast's applicability, within which the conditions described are expected; outside it the forecast should not be relied on.

The time window covered by a TAF, commonly 9, 24, or 30 hours, chosen according to the aerodrome's traffic and forecast requirements.

The Aeronautical Information Publication: the national document containing regulatory and operational information, including meteorological service arrangements and units provided.

The organisation designated by a state to supply aviation meteorological information such as observations, forecasts, and warnings to operators and air traffic services.

A global system producing harmonised upper-air forecasts, including wind and temperature and significant weather, for use by states and operators in flight planning.

The abbreviation for the World Area Forecast System, providing global gridded forecasts of upper winds and temperatures and significant en-route weather.

The unit used to describe cloud amount, dividing the sky into eighths from zero (clear) to eight (overcast), forming the basis of FEW, SCT, BKN, and OVC descriptors.

An advisory product warning pilots of hazardous conditions such as moderate or greater turbulence, icing, or low-level wind shear that may affect flight safety.

A continuous radio broadcast of meteorological information for aircraft in flight, including aerodrome observations and forecasts, useful when other data links are unavailable.