Lifted Index

Difference measured environmental and caller independently lifted surface-parcel temperatures at 500 hPa; parcel lift is not computed and index alone does not classify storm occurrence.

Description

The lifted index compares a lifted surface parcel with the surrounding atmosphere at 500 hPa.

The lifted index compares a lifted surface parcel with the surrounding atmosphere at 500 hPa. A warmer parcel gives a negative environmental-minus-parcel temperature difference.^{[1, 2]}

Difference measured environmental and caller independently lifted surface-parcel temperatures at 500 hPa; parcel lift is not computed and index alone does not classify storm occurrence.

When to use Lifted Index

Use this tool to difference measured environmental and caller independently lifted surface-parcel temperatures at 500 hPa; parcel lift is not computed and index alone does not classify storm occurrence.

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

How to use Lifted Index 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 environment500HpaTemperatureC, suppliedSurfaceParcel500HpaTemperatureC using the field table and calculation rules, then run the tool.
Read liftedIndexC. 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
environment500HpaTemperatureC	Environment500 hPa temperature c	number	Required
suppliedSurfaceParcel500HpaTemperatureC	Supplied surface parcel500 hPa temperature c	number	Required

Enter both temperatures in Celsius at the same 500-hPa level. Subtract the independently supplied parcel temperature from the environment and read the signed Celsius index.

LI = environmental 500-hPa temperature − supplied lifted surface-parcel 500-hPa temperature

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

Output field	Meaning	Value type
liftedIndexC	Lifted index c	number

json

{
  "input": {
    "environment500HpaTemperatureC": -10,
    "suppliedSurfaceParcel500HpaTemperatureC": -15
  },
  "output": {
    "liftedIndexC": 5
  }
}

Limitations and assumptions

This tool does not lift the parcel, infer moisture, or determine storm occurrence from the index.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Showalter Index: Estimate Showalter 850-hPa-origin parcel index via explicit supplied LCL and caller piecewise dry/moist lapse approximation; differs from supplied surface-parcel lifted index, not a full pseudoadiabatic solver or validated thunder forecast. For a complementary task, use K Index Severe Weather: Calculate named K index from 850/700/500-hPa temperature and measured 850/700 dewpoints; input levels must match and no severe-weather probability/recommendation follows.

Further background: Atmospheric stability index glossary.

References

Lifted Index — tool.io
Atmospheric stability index glossary — National Weather Service

Similar or alternative tools

Showalter Index
Estimate Showalter 850-hPa-origin parcel index via explicit supplied LCL and caller piecewise dry/moist lapse approximation; differs from supplied surface-parcel lifted index, not a full pseudoadiabatic solver or validated thunder forecast.
K Index Severe Weather
Calculate named K index from 850/700/500-hPa temperature and measured 850/700 dewpoints; input levels must match and no severe-weather probability/recommendation follows.