Ceilometer Cloud Layer Report Parser

Parse strict operational cloud-layer subset (FEW/SCT/BKN/OVC/VV with known three-digit heights in hundreds of feet); CLR/SKC retain no observed ceiling, no full METAR/unknown-height inference or aviation minima/safe-flight assessment.

Description

Cloud-layer reports encode sky coverage and base heights in hundreds of feet.

Cloud-layer reports encode sky coverage and base heights in hundreds of feet. Broken, overcast and vertical-visibility reports can define an observed ceiling, while few and scattered layers do not.^{[1, 2]}

When to use Ceilometer Cloud Layer Report Parser

Use this tool to parse strict operational cloud-layer subset (FEW/SCT/BKN/OVC/VV with known three-digit heights in hundreds of feet); CLR/SKC retain no observed ceiling, no full METAR/unknown-height inference or aviation minima/safe-flight assessment.

Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.

How to use Ceilometer Cloud Layer Report Parser and understand its results

Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
Enter layerReport using the field table and calculation rules, then run the tool.
Read layerCoverOktasLowerBounds, layerBaseHeightsFeet, observedCeilingFound, firstLowestCeilingFeet, hasVerticalVisibilityLayer. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
layerReport	Layer report	string	Required

Paste CLR or SKC, or 1–16 uppercase FEW/SCT/BKN/OVC/VV tokens with exactly three height digits and nondecreasing bases. Whitespace is allowed between tokens. Return lower coverage bounds 1/3/5/8 oktas, heights and the lowest ceiling; VV must stand alone. Clear reports have empty lists, found false and ceiling −1.

base height feet = three-digit height code × 100

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
layerCoverOktasLowerBounds	Layer cover oktas lower bounds	list of number
layerBaseHeightsFeet	Layer base heights feet	list of number
observedCeilingFound	Observed ceiling found	boolean
firstLowestCeilingFeet	First lowest ceiling feet	number
hasVerticalVisibilityLayer	Has vertical visibility layer	boolean

json

{
  "input": {
    "layerReport": "FEW020 SCT035 BKN100"
  },
  "output": {
    "layerCoverOktasLowerBounds": [
      1,
      3,
      5
    ],
    "layerBaseHeightsFeet": [
      2000,
      3500,
      10000
    ],
    "observedCeilingFound": true,
    "firstLowestCeilingFeet": 10000,
    "hasVerticalVisibilityLayer": false
  }
}

Limitations and assumptions

This strict subset rejects unknown heights, suffixes and full METAR text. Coverage values are lower bounds, not exact cloud fractions.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use LFC Level Free Convection: Find first strict-positive buoyancy transition at/above caller LCL in supplied linear sounding, with left-censoring or explicit no-observed-LFC sentinel; touches without positive buoyancy are not free convection. For a complementary task, use EL Equilibrium Level: Locate first upper zero crossing terminating observed positive-buoyancy layer after caller LFC search boundary; retain unobserved EL/right-censored positive layer rather than extrapolating sounding top.

Further background: Reading METAR weather reports.

References

Ceilometer Cloud Layer Report Parser — tool.io
Reading METAR weather reports — National Weather Service

Similar or alternative tools

LFC Level Free Convection
Find first strict-positive buoyancy transition at/above caller LCL in supplied linear sounding, with left-censoring or explicit no-observed-LFC sentinel; touches without positive buoyancy are not free convection.
EL Equilibrium Level
Locate first upper zero crossing terminating observed positive-buoyancy layer after caller LFC search boundary; retain unobserved EL/right-censored positive layer rather than extrapolating sounding top.