Thunderstorm types and severity
Types, least to most severe:
| Type | Source / structure | Duration / strength | Hazard / extent |
|---|---|---|---|
| Air-mass / single-cell | Afternoon heating, unstable air; forms at random, usually isolated | Short-lived: typically 1 to 2 hours | Moderate gusts and rainfall |
| Frontal (steady-state) | Lifting by front, converging winds, troughs aloft, not surface heating alone | Updrafts stronger, much longer-lasting than air-mass | Often form squall lines (PHAK ch.12) |
| Multicell | Cluster of cells in different stages | Longer-lived; can persist for hours | Covers large area (AWH 22.4) |
| Squall line | Line of storms ahead of or along a cold front; forms in moist, unstable air | Steady-state: updrafts stronger, longer-lived than air-mass | Single most intense weather hazard to aircraft (PHAK ch.12) |
| Supercell | One long-lived rotating storm | Long-lived | Biggest hail and tornadoes; nearly all produce severe weather (AWH ch.22) |
- Air-mass / single-cell: true single-cell storms rare; almost all thunderstorms multicell (AWH ch.22; PHAK ch.12).
- Multicell: lead cell matures and drifts downwind; new cell forms upwind (AWH 22.4).
- Squall line: often solid, hard to cross; can form far from any front.
- Squall line: can run hundreds of miles: too wide and severe to penetrate, too long to detour.
Severe: cloud tops 35,000 ft or higher (TC AIM AIR 2.7.2).
Trap: severity comes from cloud tops, not storm type.
References
- FAA Aviation Weather Handbook (FAA-H-8083-28)
- FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), ch.12
- TC AIM AIR 2.7.2 (thunderstorm avoidance: considerations)