Showalter Index is a measure of thunderstorm potential and severity. Especially useful when a shallow, cool layer of air below 850 mb conceals greater convective potential above.
| > 4 | Stable.Thunderstorms Unlikely |
| 1 to 3 | Marginally unstable. Thunderstorms possible.- trigger needed |
| -2 to 0 | Moderately unstable. Increasing Chance of Thunderstorms. |
| -3 to -2 | High Potential of Thunderstorms |
| -5 to -4 | Very unstable. |
| -10 to -6 | Extremely unstable. |
| < -10 | Run For Your Life. |
Other UKAWC Stability Indices:
| Lifted Index (LI) | CAPE | K-Index | CIN | SWEAT | Total Totals |
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