Supercell Composite Parameter Calculator

Named effective-layer SCP:MUCAPE/1000×ESRH/50×shearFactor(0below10m/s, min(s,20)/20); independently sounding-derived terms, no tornado occurrence/probability. Caller independently establishes matching units, evidence, method edition and applicability; output is not compliance, diagnosis, work-safety approval, geological identity or validated hazard prediction.

Description

The effective-layer supercell composite combines instability, helicity and wind shear terms.

The effective-layer supercell composite combines instability, helicity and wind shear terms.^{[1, 2]}

It is a model index from sounding-derived inputs rather than a probability of a storm or tornado.

When to use Supercell Composite Parameter Calculator

Use this tool to calculate or review the supplied observations under the stated rules. Match the observation method, units, averaging period and independently established reference.

How to use Supercell Composite Parameter Calculator and understand its results

Match the observation method, units, averaging period and independently established reference.
Enter mostUnstableCapeJKg, effectiveStormRelativeHelicityM2S2, effectiveBulkShearMS, using the field meanings and rules below, then run the tool.
Read effectiveLayerSupercellComposite. Inspect nested result fields where present, and review unknown records separately from known matches.
Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.

Input field	Meaning	Value type	Requirement
mostUnstableCapeJKg	Most unstable cape j kg	number	Required
effectiveStormRelativeHelicityM2S2	Effective storm relative helicity m2 s2	number	Required
effectiveBulkShearMS	Effective bulk shear m s	number	Required

Require nonnegative MUCAPE in J/kg, effective storm-relative helicity in m²/s² and effective bulk shear in m/s. Multiply CAPE/1000 by helicity/50 and a shear factor: zero below 10, shear/20 from 10 to 20 inclusive, and one above 20. At 10 the factor is .5, so the implemented branch is discontinuous there.

SCP=(MUCAPE/1000)(ESRH/50)×[0 if shear<10, min(shear,20)/20 otherwise]

Use the matching field units and the exact boundary, ordering and reference rules above.

Output field	Meaning	Value type
effectiveLayerSupercellComposite	Effective layer supercell composite	number

json

{
  "input": {
    "mostUnstableCapeJKg": 1000,
    "effectiveStormRelativeHelicityM2S2": 50,
    "effectiveBulkShearMS": 15
  },
  "output": {
    "effectiveLayerSupercellComposite": 0.75
  }
}

Limitations and assumptions

The observations and reference conditions must be independently established. This result is a record summary or stated model screen, not an official warning or a validated event forecast.

Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite.

Alternative or Complementary methods

For a related step, use Tropical Depression vs Storm Wind Classifier: A tropical wind-stage screen uses a declared maximum sustained wind convention. For a complementary comparison, use Zonal Index Circulation Strength Calculator: A zonal circulation index can summarize eastward flow around a matched ring.

References

Supercell Composite Parameter Calculator — tool.io
Mesoscale Parameters — National Weather Service

Similar or alternative tools

Tropical Depression vs Storm Wind Classifier
A tropical wind-stage screen uses a declared maximum sustained wind convention.
Zonal Index Circulation Strength Calculator
A zonal circulation index can summarize eastward flow around a matched ring.