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AutomaticCloud Information
A report from anAWSwith a cloud sensorwill include data from this sensor
if the report is fully automated (inwhich case the abbreviationAUTO is
also included in themessage). The datawill be in the same form asmanual
reports except that:
• NCDwill be reported if no cloud is detected; and
• therewill beno indication of cumulonimbus or towering cumulus.
Note: Pilots should exercise cautionwhen interpreting automated cloud
information as itmay not be equivalent to a humanobservation
because:
• The information is reported as a 30minute averagewithdoubleweighting
given to the last 10minutes; and
• As it is sourced from a single ceilometer samplingonly the sky directly
overhead, itmay not be representative of the skyline.
Fully automatedAWSmay issue special reports (SPECI) for cloudusing data
from cloud sensors.
CAVOK
CAVOK is included in reports (from staffed stations only) and forecastswhen
the following conditions are observed, or forecast tooccur, simultaneously:
• visibility of 10 km ormore;
• nil significant cloud, i.e. no cloud below 5000 ft or below the
highest 25 nmminimum sector altitude, whichever is greater, and no
cumulonimbus or towering cumulus at any height; and
• nil significantweather.
When the termCAVOK is given, the elements visibility, weather and cloud
will not be given.
Whenever a total of BKN ormore of low ormiddle cloud cover is at or above
5000 ft, andCAVOK has been used, the cloud amount andbasemay be given
as a remark (i.e. after RMK).
Significant Variation
Aerodrome forecastswill include significant changes or variations (indicated
by FM, BECMG, INTER and TEMPO) to the previously given conditions
when the relevant criteria aremet. These relate to improvements aswell as
deteriorations.
2 – me t eorology
aerodrome forecasts and reports