Thunderstorm Watch/Warning

Severe Thunderstorm Criteria

MetService uses the following criteria for severe thunderstorms in New Zealand:

Heavy rain (from thunderstorms):
Rainfall of 25 millimetres per hour, or more.
Large hail:
Hailstones 20 millimetres in diameter, or larger.
Strong wind gusts (from thunderstorms):
Gusts of 110 kilometres per hour (60 knots) or stronger.
Damaging tornadoes:
Fujita F1 (wind speeds greater than 116 kilometres per hour (63 knots)) or stronger.

Note: some tornadic systems such as funnel clouds, waterspouts and small land-based tornadoes are possible with thunderstorms that may not be classified as severe.