========================== Introduction ========================== This document provides guidance on how abbreviations and codes from the Traditional Alphanumeric Codes (TAC) are represented in XML (IWXXM). ========================== METAR/SPECI ========================== NIL (report) (Represented as a status of "MISSING" on METAR/SPECI and TAF reports) CAVOK - Cloud and visibility OK When CAVOK conditions apply, the appropriate Record type shall have "cloudAndVisibilityOK" set to true and visibility, runway visual range, weather, and cloud information shall be missing. CLRD - Runway contamination is cleared When runway contamination has been cleared, AerodromeRunwayState shall have "cleared" set to true NSC - No clouds of operational significance When no cloud of operational significance is observed/forecast, and no restriction on vertical visibility and 'CAVOK' is not appropriate, the cloud group shall be missing with a nil reason of http://codes.wmo.int/common/nil/nothingOfOperationalSignificance NCD - No clouds detected (by auto system) When no clouds are detected by the automatic observing system, it shall be indicated by a missing cloud group with a nil reason of http://codes.wmo.int/common/nil/notDetectedByAutoSystem NOSIG - No significant changes are forecast When no change is expected to occur, this shall be indicated by a single missing trend forecast with a nil reason of http://codes.wmo.int/common/nil/noSignificantChange NSW - No weather of operational significance The expected end of occurrence of weather phenomena shall be indicated by a change forecast with a missing weather group with a nil reason of http://codes.wmo.int/common/nil/nothingOfOperationalSignificance R88 (runway designator for runway state) When all runways are being indicated, the AerodromeRunwayState shall have "allRunways" set to true R99 (runway designator for runway state) When a new runway state report is not available in time for dissemination of the METAR message, the previous runway state report will be repeated SNOCLO - Runway closed due to snow When a runway is closed due to snow, AerodromeRunwayState shall have "snowClosure" set to true Present weather "//" When present weather cannot be observed by the automatic observing system due to a temporary failure of the system/sensor, the present weather shall be missing with a nil reason of http://codes.wmo.int/common/nil/notObservable Vertical visibility "VV///" (METAR/SPECI observations) When the sky is obscured and the value of the vertical visibility cannot be determined by the automatic observing system due to a temporary failure of the system/sensor, the vertical visibility shall be missing with a nil reason of http://codes.wmo.int/common/nil/notObservable Cloud amount and base "//////" When cumulonimbus clouds or towering cumulus clouds are detected by the automatic observing system and the cloud amount and the height of cloud base cannot be observed, this shall be indicated by a missing cloud layer with a nil reason of either http://codes.wmo.int/common/nil/notObservable if the value could not be observed due to a sensor or system failure, or http://codes.wmo.int/common/nil/notDetectedByAutoSystem if the automated system is working properly but did not observe any values Cloud amount "///015" When cumulonimbus clouds or towering cumulus clouds are detected by the automatic observing system and the cloud amount cannot be observed, this shall be indicated by a CloudLayer with a missing "amount" with a nil reason of either http://codes.wmo.int/common/nil/notObservable if the value could not be observed due to a sensor or system failure, or http://codes.wmo.int/common/nil/notDetectedByAutoSystem if the automated system is working properly but did not observe any values Cloud base "BKN///" When cumulonimbus clouds or towering cumulus clouds are detected by the automatic observing system and the height of cloud base cannot be observed, this shall be indicated by a CloudLayer with a missing "base" with a nil reason of either http://codes.wmo.int/common/nil/notObservable if the value could not be observed due to a sensor or system failure, or http://codes.wmo.int/common/nil/notDetectedByAutoSystem if the automated system is working properly but did not observe any values Cloud type "///" When cloud type cannot be observed by an auto system due to sensor limitations this shall be indicated by http://codes.wmo.int/common/nil/notObservable. Runway depth of deposit "//" When the runway depth of deposits is operationally insignificant or is not measurable this shall be indicated by a missing depthOfDeposits and a nilReason of either http://codes.wmo.int/common/nil/notObservable or http://codes.wmo.int/common/nil/nothingOfOperationalSignificance. Runway depth of deposit "99" (value from WMO code table 1079) When the runway depth of deposits is not reported due to runway or runways non-operational due to snow, slush, ice, large drifts or runway clearance this shall be indicated by a missing depthOfDeposits and a nilReason of http://www.opengis.net/def/nil/OGC/0/unknown. ========================== TAF ========================== NIL (report) (Represented as a status of "MISSING" on METAR/SPECI and TAF reports) CAVOK - Cloud and visibility OK When CAVOK conditions apply, the appropriate Record type shall have "cloudAndVisibilityOK" set to true and visibility, runway visual range, weather, and cloud information shall be missing. NSC - No clouds of operational significance When no cloud of operational significance is observed/forecast, and 'CAVOK' is not appropriate, the cloud group shall be missing with a nil reason of http://codes.wmo.int/common/nil/nothingOfOperationalSignificance NSW - No weather of operational significance The expected end of occurrence of weather phenomena shall be indicated by a change forecast with a missing weather group with a nil reason of http://codes.wmo.int/common/nil/nothingOfOperationalSignificance Vertical visibility "VV///" When the vertical visibility is not available for any reason, vertical visibility shall be missing with no nil reason. ========================== SIGMET ========================== NO VA EXP - No volcanic ash expected The expected end of occurrence of volcanic ash shall be indicated with a missing VolcanicAshSIGMET "phenomenon" with a nil reason of http://codes.wmo.int/common/nil/nothingOfOperationalSignificance ========================== Volcanic Ash Advisory ========================== 'UNKNOWN' volcano name An unknown volcano name shall be indicated with an EruptingVolcano name of "UNKNOWN" 'UNNAMED' volcano name An unnamed volcano shall be indicated with an EruptingVolcano name of "UNNAMED" 'UNKNOWN' volcano location An unknown volcano location shall be indicated with a missing EruptingVolcano position with a nilReason of "unknown" 'UNKNOWN' aviation colour code An unknown aviation colour code shall be indicated with a missing colourCode with a nilReason of "unknown" 'NOT GIVEN' aviation colour code An aviation colour code that is not given shall be indicated with a missing colourCode with a nilReason of "withheld" 'NIL' aviation colour code A NIL aviation colour code shall be indicated with a missing colourCode with a nilReason of "missing" 'VA NOT IDENTIFIABLE FM SATELLITE DATA' Unidentifiable volcanic ash from satellite data shall be indicated with a nil ashCloudExtent with a nilReason of "unknown" 'NO VA EXP' When no volcanic ash is expected it shall be indicated with a nil ashCloudExtent with a nilReason of http://codes.wmo.int/common/nil/nothingOfOperationalSignificance 'NOT AVBL' When volcanic ash is not available it shall be indicated with a nil ashCloudExtent with a nilReason of 'missing' 'NOT PROVIDED' When volcanic ash is not provided it shall be indicated with a nil ashCloudExtent with a nilReason of 'withheld' ========================== Tropical Cyclone Advisory ========================== '