What Weighted Cloud Cover represents
A weighted mean lets area, duration, confidence, or another declared importance measure control each estimate's contribution. Weights need only share a common relative scale.
Weighted Cloud Cover begins with cover estimate 1, weight 1, cover estimate 2, weight 2, cover estimate 3, weight 3. Mark each value as observed, remotely sensed, modeled, assumed, or derived, and preserve its valid time and spatial support.
Uncertainty and sensitivity
Vary the least certain Weighted Cloud Cover input over a credible range and retain the resulting spread in weighted cloud cover. Display precision cannot overcome observer classification, retrieval uncertainty, spatial variability, or an empirical coefficient.
A Weighted Cloud Cover sensitivity range is not automatically a probability interval. It omits correlations, model-form error, sampling mismatch, sub-grid cloud structure, nonuniform visibility paths, and uncertainty outside the entered variables.
Visibility and contrast conventions
Visibility from Weighted Cloud Cover depends on the target contrast threshold and extinction units. Meteorological optical range fixes a two-percent contrast convention; a general contrast range or runway screening estimate may use another threshold.
Do not equate Weighted Cloud Cover optical distance with prevailing visibility, slant range, night visual range, or official RVR without the required observation and processing conventions.
Continue the Weighted Cloud Cover workflow with the related Fog Visibility Calculator, keeping the same observation support and conventions.
Solar geometry and radiation conventions
Solar elevation is measured above the geometric horizon, while azimuth here is clockwise from true north. Weighted Cloud Cover must retain whether radiation is normal to the rays or incident on a horizontal surface.
Civil time is not solar hour angle. Longitude, time zone, equation of time, atmospheric refraction, shading horizon, and surface tilt belong in Weighted Cloud Cover only when the displayed model explicitly includes them.
Keeping an auditable record
Save raw Weighted Cloud Cover inputs, conversions, constants, coefficient sources, formula version, unrounded output, rounded result, and quality flags. A reviewer should reproduce the number without guessing a cover, angle, contrast, or height convention.
If a source value or assumption changes, create a dated Weighted Cloud Cover revision. Preserve the earlier output and label whether the change is a correction, a new observation, or a separate scenario.
Formula and convention
The working relationship is C_w = Σ(w_iC_i) ÷ Σw_i. Weighted Cloud Cover uses only the displayed entries and does not retrieve imagery, station observations, ephemerides, forecasts, or runway systems.
Keep percentages as percentages at entry and convert them to fractions only where the formula shows it. For Weighted Cloud Cover, retain angle direction, optical threshold, height reference, and distance unit with the answer.
Checked numerical example
Covers 30%, 60%, and 90% with weights 1, 2, and 1 produce exactly 60%.
Reset restores this Weighted Cloud Cover example. Repeat it independently with the stated constants and rounding before replacing demonstration values with observations or scenarios.
Collecting compatible inputs
Choose one defensible weighting basis and use it consistently. Do not mix square-kilometre area for one value with quality scores for another without a defined normalization.
Record site, coordinates, elevation, timestamp, time zone, path direction, wavelength or sensor band, target definition, cloud-layer method, solar-time convention, averaging period, and quality flags when relevant to Weighted Cloud Cover.
Interpreting Weighted cloud cover
The result stays between the smallest and largest entered cover when weights are nonnegative. A doubled weight gives that observation twice the influence.
Compare Weighted Cloud Cover outputs only after aligning reference height, sky footprint, path, illumination, contrast convention, and temporal average. Similar numbers can describe different optical or geometric quantities.
Boundary and monotonic checks
At least one weight must be positive; zero-weight values make no contribution.
For Weighted Cloud Cover, change one input at a time and predict whether the answer should rise, fall, or remain fixed. Unexpected behavior can expose percent-fraction, degree-radian, metre-kilometre, or layer-order mistakes.
Continue the Weighted Cloud Cover workflow with the related Visibility from Extinction Coefficient Calculator, keeping the same observation support and conventions.
Where the model stops
A weighted mean does not model vertical cloud overlap and can hide spread. Retain the three source values and weights alongside the combined percentage.
Weighted Cloud Cover is transparent educational arithmetic, not a cloud observation, weather forecast, solar-resource assessment, flight rule, runway visual range report, instrument calibration, or operational safety authority.
Frequent clouds and visibility errors
Typical Weighted Cloud Cover errors include mixing oktas and tenths, confusing AGL with MSL, adding overlapping layers, treating degrees as radians, using sea-level-reduced visibility, or applying a two-percent constant to a five-percent threshold.
Reject impossible Weighted Cloud Cover combinations rather than forcing an answer. Keep a clear zero distinct from missing or obscured sky, preserve signs on hour angle, and verify every inverse distance and logarithm denominator before downstream use.
Cloud and visibility questions
What does Weighted Cloud Cover report?
Weighted Cloud Cover reports weighted cloud cover from the displayed inputs and formula.
Can forecast or scenario inputs be used?
Yes. Label the Weighted Cloud Cover output as a scenario; the page does not fetch or validate a forecast.
How can I verify Weighted Cloud Cover?
Repeat C_w = Σ(w_iC_i) ÷ Σw_i with the recorded conversions, then test the checked example and a physical boundary.
Why could another source disagree?
Another source may use different cloud overlap, optical threshold, solar convention, coefficient, sensor path, height reference, or rounding than Weighted Cloud Cover uses.
Is this an operational visibility or aviation value?
No. Weighted Cloud Cover does not replace official weather observations, RVR systems, flight procedures, warnings, or qualified judgment.
How should the result be rounded?
Keep full precision inside Weighted Cloud Cover, then round no more finely than the least certain measurement or model assumption supports.
When should I recalculate?
Recalculate Weighted Cloud Cover when its site, time, path, layer, sky footprint, illumination, source observation, or model assumption changes.