K-index (meteorology)
The K-Index or George's Index is a measure of
temperature lapse rate, moisture content of the lower atmosphere, and the vertical extent of the moist layer."[1] It was developed by the American meteorologist Joseph J. George, and published in the 1960 book Weather Forecasting for Aeronautics.[2]
Definition
The index is derived arithmetically by:[3]
Where :
- = Dew point at 850 hPa
- = Temperature at 850 hPa
- = Dew point at 700 hPa
- = Temperature at 700 hPa
- = Temperature at 500 hPa
Interpretation
The K Index is related to the probability of occurrence of a thunderstorm. It was developed with the idea that Potential = 4 x (KI - 15), which gives the following interpretation:[1][4]
| K-index values vs. Thunderstorm Probability | ||
|---|---|---|
| K-index value (in °C) | Thunderstorm Probability | |
| Less than 20 | None | |
| 20 to 25 | Isolated thunderstorms | |
| 26 to 30 | Widely scattered thunderstorms | |
| 31 to 35 | Scattered thunderstorms | |
| Above 35 | Numerous thunderstorms | |
References
- ^ a b "K-Index". weather.gov. National Oceanic and Atmospheric Administration. Archived from the original on July 5, 2015. Retrieved July 5, 2015.
- ^ J.J. George (1960). Weather Forecasting for Aeronautics. New York City: Academic Press. p. 673.
- ^ Sirvatka. "Stability Indices". Notes de cours. College of DuPage. Retrieved October 30, 2015.
- ^ Canadian Meteorological Centre. "Stability Indices". Formation des météorologues. Meteorological Service of Canada. Retrieved October 30, 2015.