AerodromeCondition-cavok
type: Class
subclass of: AerodromeCondition
comment: Visibility, cloud and present weather better than prescribed values or conditions.

Cloud-isAmoutAndBaseNotObservable
type: Class
subclass of: Cloud
comment: Indication that cumulonimbus clouds or towering cumulus clouds are detected by the automatic observing system but the cloud amount and the height of cloud base cannot be observed.

Cloud-isEmbedded
type: Class
subclass of: Cloud
comment: Surrounded, or part of a wider cloud layer, in opposition to isolated.

Cloud-isNoCloudDetected
type: Class
subclass of: Cloud
comment: No clouds are detected by the automatic observing system.

Cloud-isNoSignificantCloudDetected
type: Class
subclass of: Cloud
comment: No clouds of operational significance are detected by the ceilometer(s) in reports from fully automatic observing systems.

Cloud-isObscured
type: Class
subclass of: Cloud
comment: Hidden or out of sight by haze, smoke or cloud for example.

Cloud-isWidespread
type: Class
subclass of: Cloud
comment: Affecting a large area.

http://project-best.eu/owl/airm-mod/meteorology#HorizontalVisibility-isPrevailingVisibilityAbove10000metres
type: Class
subclass of: HorizontalVisibility
comment: Indication that the prevailing visibility is of at least 10000 meters.

HorizontalVisibility-isUnidirectionalVisibility
type: Class
subclass of: HorizontalVisibility
comment: Indication whether the horizontalVisibility is given for a single direction or not.

MovementDescription-isStationary
type: Class
subclass of: MovementDescription
comment: Indication whether a meteorological phenomenon is moving or not.

VolcanicActivity-isErupting
type: Class
subclass of: VolcanicActivity
comment: Indication wether a volcano is erupting or not.

WeatherCondition-hasNoSignificantWeather
type: Class
subclass of: WeatherCondition
comment: Indication that no specified en-route weather phenomena which may affect the safety of aircraft operations is occurring or expected to occur.

Wind-isCalm
type: Class
subclass of: Wind
comment: Indication that the wind is forecast to be less than 0.5 m/s (1 kt).

Wind-isVariable
type: Class
subclass of: Wind
comment: Indication that the direction of the wind changes frequently. According to Annex 3 the wind is reported as variable (VRB) in local routine or special reports, in METAR and SPECI, when one of the following situations occur: - when the total variation is 60 or more and less than 180 and the wind speed is less than 1.5 m/s (3 kt), the wind direction shall be reported as variable with no mean wind direction; or - when the total variation is 180 or more, the wind direction shall be reported as variable with no mean wind direction.

BECMG
type: NamedIndividual
type: CodeChangeIndicatorType
comment: A code used to describe changes where the meteorological conditions are expected to reach or pass through specified threshold values at a regular or irregular rate and at an unspecified time during the time period.

NOSIG
type: NamedIndividual
type: CodeChangeIndicatorType
comment: No significant changes are forecast with respect to the current meteorological conditions.

TEMPO
type: NamedIndividual
type: CodeChangeIndicatorType
comment: A code used to describe expected frequent or infrequent temporary fluctuations in the meteorological conditions which reach or pass specified threshold values and last for a period of less than one hour in each instance and, in the aggregate, cover less than one-half of the forecast period during which the fluctuations are expected to occur.

BROKEN
type: NamedIndividual
type: CodeCloudAmountType
comment: (5 to 7 oktas)

FEW
type: NamedIndividual
type: CodeCloudAmountType
comment: (1 to 2 oktas)

OVERCAST
type: NamedIndividual
type: CodeCloudAmountType
comment: (8 oktas)

SCATTERED
type: NamedIndividual
type: CodeCloudAmountType
comment: (3 to 4 oktas)

SCATTERED_BROKEN
type: NamedIndividual
type: CodeCloudAmountType
comment: SCATTERED or BROKEN

SKY_CLEAR
type: NamedIndividual
type: CodeCloudAmountType
comment: (0 oktas)

ALTOCUMULUS
type: NamedIndividual
type: CodeCloudType
comment: White or grey, or both white and grey, patch, sheet or layer of cloud, generally with shading, composed of laminae, rounded masses, rolls, etc., which are sometimes partly fibrous or diffuse and which may or may not be merged; most of the regularly arranged small elements usually have an apparent width of between one and five degrees.

ALTOSTRATUS
type: NamedIndividual
type: CodeCloudType
comment: Greyish or bluish cloud sheet or layer of striated, fibrous or uniform appearance, totally or partly covering the sky, and having parts thin enough to reveal the Sun at least vaguely, as through ground glass. Altostratus does not show halo phenomena.

CIRROCUMULUS
type: NamedIndividual
type: CodeCloudType
comment: Thin, white patch, sheet or layer of cloud without shading, composed of very small elements in the form of grains, ripples, etc., merged or separated, and more or less regularly arranged; most of the elements have an apparent width of less than one degree.

CIRROSTRATUS
type: NamedIndividual
type: CodeCloudType
comment: Transparent, whitish cloud veil of fibrous (hair-like) or smooth appearance, totally or partially covering the sky, and generally producing halo phenomena.

CIRRUS
type: NamedIndividual
type: CodeCloudType
comment: Detached clouds in the form of white, delicate filaments or white or mostly white patches or narrow bands. These clouds have a fibrous (hair-like) appearance, or a silky sheen, or both.

CUMULONIMBUS
type: NamedIndividual
type: CodeCloudType
comment: Dense and heavy cloud with a considerable mountain- or tower-shaped vertical extension. These clouds, the base of which is quite dark, may give rise to thunderstorms and generally heavy precipitation in the form of rain, snow, fine or large hail, sometimes accompanied by strong wind gusts.

CUMULUS
type: NamedIndividual
type: CodeCloudType
comment: Detached cloud, generally dense and with sharp outlines, developing vertically in the form of rising mounds, domes or towers, of which the bulging upper part is often like a cauliflower. The sunlit parts are mostly brilliant white and the base is relatively dark and nearly horizontal. Sometimes Cumulus clouds are ragged.

NIMBOSTRATUS
type: NamedIndividual
type: CodeCloudType
comment: Grey cloud layer, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground. It is thick enough throughout to blot out the Sun. Low, ragged clouds frequently occur below the layer, with which they may or may not merge.

STRATOCUMULUS
type: NamedIndividual
type: CodeCloudType
comment: Banks or a layer of grey or whitish clouds generally caught on mountaintops. The base may be fuzzy or smooth and generally horizontal.

STRATUS
type: NamedIndividual
type: CodeCloudType
comment: Generally grey cloud layer with a fairly uniform base, which may give drizzle, ice prisms or snow grains. When the Sun is visible through the cloud, its outline is clearly discernible; Stratus does not produce halo phenomena except, possibly, at very low temperatures; sometimes it appears in the form of ragged patches.

TOWERING_CUMULUS
type: NamedIndividual
type: CodeCloudType
comment: A descriptive term, used mostly in weather observing, for cumulus congestus (Cu con).

CONSTANT
type: NamedIndividual
type: CodeConvectionCellTopVariationType
comment: Indicates no sensible variation of the top altitude of a convection cell.

DECAYING
type: NamedIndividual
type: CodeConvectionCellTopVariationType
comment: Indicates that the top altitude of a convection cell is lowering.

GROWING
type: NamedIndividual
type: CodeConvectionCellTopVariationType
comment: Indicates that the top altitude of a convection cell is increasing.

CELL_BASE
type: NamedIndividual
type: CodeConvectionCellType
comment: The base (cell base) of a cell.

CELL_TOP
type: NamedIndividual
type: CodeConvectionCellType
comment: The upper part of a cell (cell top).

DUST
type: NamedIndividual
type: CodeObscurationType
comment: Earth or other solid matter in a minute and fine state of subdivision, so that the particles are small and light enough to be easily raised and carried in a cloud by the wind; any substance comminuted or pulverized; powder.

FOG
type: NamedIndividual
type: CodeObscurationType
comment: A suspension of very small, usually microscopic water droplets in the air, reducing visibility at the Earth's surface.

HAZE
type: NamedIndividual
type: CodeObscurationType
comment: Suspension in the atmosphere of extremely small, dry particles which are invisible to the naked eye but numerous enough to give the sky an opalescent appearance.

MIST
type: NamedIndividual
type: CodeObscurationType
comment: Suspension in the air of microscopic water droplets or wet hygroscopic particles which reduce the visibility at the Earth's surface.

SAND
type: NamedIndividual
type: CodeObscurationType
comment: A material consisting of comminuted fragments and water-worn particles of rocks (mainly silicious) finer than those of which gravel is composed.

SMOKE
type: NamedIndividual
type: CodeObscurationType
comment: Suspension in the atmosphere of small particles produced by combustion.

SPRAY
type: NamedIndividual
type: CodeObscurationType
comment: Ensemble of water droplets torn by the wind from the surface of an extensive body of water, generally from the wave crests, and carried up a short distance into the air.

UNIDENTIFIED
type: NamedIndividual
type: CodeObscurationType
comment: That has not been identified; of which the identity has not been established.

VOLCANIC_ASH
type: NamedIndividual
type: CodeObscurationType
comment: Extremely fine particles of pulverized rock, the composition of which, generally speaking, is comprised predominantly of silica (> 50 per cent), together with smaller amounts of the oxides of aluminium, iron, calcium and sodium.

DRIZZLE
type: NamedIndividual
type: CodePrecipitationType
comment: Fairly uniform precipitation in very fine drops of water (diameter less than 0.5 mm) very close to one another, falling from a cloud.

HAIL
type: NamedIndividual
type: CodePrecipitationType
comment: Precipitation of either transparent, or partly or completely opaque particles of ice (hailstones), usually spheroidal, conical or irregular in form and of diameter very generally between 5 and 50 millimetres, which falls from a cloud either separately or agglomerated into irregular lumps.

ICE_CRYSTALS
type: NamedIndividual
type: CodePrecipitationType
comment: Any one of a number of macroscopic crystalline forms of ice including hexagonal columns and platelets, dendritic crystals, ice needles and their combinations.

ICE_PELLETS
type: NamedIndividual
type: CodePrecipitationType
comment: Precipitation of transparent particles of ice which are spherical or irregular, rarely conical, and which have a diameter of 5 mm or less.

RAIN
type: NamedIndividual
type: CodePrecipitationType
comment: Precipitation of liquid water particles, either in the form of drops of more than 0.5 mm in diameter, or of smaller widely scattered drops.

SMALL_HAIL
type: NamedIndividual
type: CodePrecipitationType
comment: Precipitation of translucent ice particles, which falls from a cloud. These particles are almost always spherical and sometimes have conical tips. Their diameter may attain or even exceed five millimetres.

SNOW
type: NamedIndividual
type: CodePrecipitationType
comment: Precipitation of ice crystals, isolated or agglomerated, falling from a cloud.

SNOW_GRAINS
type: NamedIndividual
type: CodePrecipitationType
comment: Precipitation of very small opaque white particles of ice which fall from a cloud and which are fairly flat or elongated with diameters generally less than 1 mm.

UNIDENTIFIED
type: NamedIndividual
type: CodePrecipitationType
comment: Unidentified precipitation.

UNKNOWN
type: NamedIndividual
type: CodePrecipitationType
comment: Unknown precipitation.

MIDDLE
type: NamedIndividual
type: CodeRVRReadingType
comment: Middle or centre of runway.

TAKEOFF
type: NamedIndividual
type: CodeRVRReadingType
comment: Take-off or rollout point.

TOUCHDOWN
type: NamedIndividual
type: CodeRVRReadingType
comment: Touchdown

D
type: NamedIndividual
type: CodeRVRTendencyType
comment: Downward RVR tendency

N
type: NamedIndividual
type: CodeRVRTendencyType
comment: No RVR change tendency

U
type: NamedIndividual
type: CodeRVRTendencyType
comment: Upward RVR tendency

CALM_GLASSY
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres = 0

CALM_RIPPLED
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 0 and 0.1

HIGH
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 6 and 9

MODERATE
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 1.25 and 2.5

PHENOMENAL
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres over 14

ROUGH
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 2.5 and 4

SLIGHT
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 0.5 and 1.25

SMOOTH_WAVELETS
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 0.1 and 0.5

VERY_HIGH
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 9 and 14

VERY_ROUGH
type: NamedIndividual
type: CodeSeaStateType
comment: Height in metres between 4 and 6

BLOWING
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Raised by the wind to a moderate height above the ground (2 meters or more).

FREEZING
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Precipitation freezing on impact on the ground and on exposed objects.

LOW_DRIFTING
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: In motion due to the action of wind or raised by the wind to a small height above the ground (less than 2 meters).

PARTIAL
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Covering part of the aerodrome.

PATCHES
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Occurrences over small areas.

PROXIMITY
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: The weather phenomenon is observed between approximately 8 km and 16 km from the aerodrome reference point.

SHALLOW
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Has a very little vertical extent.

SHOWER
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Precipitation, often short-lived and heavy, falling from convective clouds. A shower is characterized by its sudden beginning and ending, and generally by large and rapid changes of intensity.

THUNDERSTORM
type: NamedIndividual
type: CodeSignificantWeatherQualifierType
comment: Sudden electrical discharges manifested by a flash of light (lightning) and a sharp or rumbling sound (thunder). Thunderstorms are associated with convective clouds (Cumulonimbus) and are, more often, accompanied by precipitation in the form of rainshowers or hail, or occasionally snow, snow pellets, or ice pellets.

CLEAR_AIR_TURBULENCE
type: NamedIndividual
type: CodeTurbulenceType
comment: Upper-atmospheric turbulence encountered by an aircraft when flying through clear air.

IN_CLOUD_TURBULENCE
type: NamedIndividual
type: CodeTurbulenceType
comment: Upper-atmospheric turbulence encountered by an aircraft when flying through a cloud.

BETWEEN_11_AND_25_PERCENT
type: NamedIndividual
type: CodeValueContaminationExtentType
comment: Between 11% and 25%

BETWEEN_26_AND_50_PERCENT
type: NamedIndividual
type: CodeValueContaminationExtentType
comment: Between 26% and 50%

LESS_THAN_10_PERCENT
type: NamedIndividual
type: CodeValueContaminationExtentType
comment: Less than 10%

MORE_THAN_50_PERCENT
type: NamedIndividual
type: CodeValueContaminationExtentType
comment: More than 50%

HEAVY
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A heavy intensity.

LIGHT
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A light intensity.

LIGHT_MODERATE
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A light to moderate intensity.

MODERATE
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A moderate intensity.

MODERATE_SEVERE
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A moderate to severe intensity.

NONE
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A report of no intensity (no icing present, for example) for a condition. This is different from missing information.

SEVERE
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A severe intensity.

UNKNOWN
type: NamedIndividual
type: CodeWeatherIntensityType
comment: A report of unknown intensity.

DUST_STORM
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: An ensemble of particles of dust energetically lifted to great heights by a strong and turbulent wind.

DUST_WHIRL
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: An ensemble of particles of dust or sand, sometimes accompanied by small litter, raised from the ground in the form of a whirling column of varying height with a small diameter and an approximately vertical axis.

FUNNEL_CLOUD
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: Cloud formed at the core of a waterspout or tornado vortex, sometimes extending right down to the ground, caused by the reduction of pressure at the centre of the vortex.

LIGHTNING
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: Luminous manifestation accompanying a sudden electrical discharge which takes place from or inside a cloud or, less often, from high structures on the ground or from mountains.

MOUNTAIN_OBSCURATION
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: Description of a visibility condition that is distinguished from IFR because ceilings, by definition, are described as "above ground level" (AGL). In mountainous terrain clouds can form at altitudes significantly higher than the weather reporting station and at the same time nearby mountain tops may be obscured by low visibility. In these areas the ground level can also vary greatly over a small area.

MOUNTAIN_WAVE
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: Atmospheric internal gravity waves, which are periodic changes of atmospheric pressure, temperature and orthometric height in a current of air.

RADIOACTIVE_CLOUD
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: A radioactive particulate contaminated atmospheric area.

SANDSTORM
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: An ensemble of particles of sand energetically lifted to great heights by a strong and turbulent wind.

SQUALL
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: Atmospheric phenomenon characterized by an abrupt and large increase of wind speed with a duration of the order of minutes which diminishes rather suddenly. It is often accompanied by showers or thunderstorms.

TEMPERATURE_INVERSION
type: NamedIndividual
type: CodeWeatherPhenomenonType
comment: Vertical temperature distribution such that temperature increases with height.

100_KNOTS
type: NamedIndividual
type: CodeWindCharacteristicType
comment: Forecasted wind on airport surface is more than 100kt (200 Km/h)

CALM
type: NamedIndividual
type: CodeWindCharacteristicType
comment: Wind direction on airport surface is irrelevant, wind is less than 1kt

NORMAL
type: NamedIndividual
type: CodeWindCharacteristicType
comment: Wind on airport surface is normally described through the direction attribute

VRB
type: NamedIndividual
type: CodeWindCharacteristicType
comment: Wind direction on airport surface is variable