Severe Weather Outlook

Valid from Wednesday 26-Feb-2020 to Saturday 29-Feb-2020

Issued: 2:53pm Monday 24 Feb 2020

On Thursday, a front should move northeast over Fiordland and then onto Westland where it may become slow moving. This front delivers a period of heavy rain to Fiordland and Westland, and strong north to northwesterly winds. Another front then approaches Fiordland from the west late Friday, then moves northeast across across the South Island on Saturday delivering another burst of heavy rain and strong north to northwesterly winds.

On Thursday, there is low confidence of rainfall amounts reaching warning criteria in Fiordland, and moderate confidence for Westland on Thursday and Friday. Late Friday and during Saturday, there is low confidence of warning amounts of rain for Fiordland, Westland and Buller as depicted on the chart. In addition, there is low confidence of north to northwesterly winds reaching severe gale in exposed parts of Fiordland and Southland at times during Thursday, Friday and Saturday.

Low confidence:

a 20% likelihood (or 1 chance in 5) that the event will actually happen.

Moderate confidence:

a 40% likelihood (or 2 chances in 5) that the event will actually happen.

High confidence:

a 60% likelihood (or 3 chances in 5) that the event will actually happen.

New issues of this forecast are made available on this site at or before 16:30 NZST

Thunderstorm Outlook

Valid to Midnight Tuesday, 25-Feb-2020

Issued: 8:33pm Monday 24 Feb 2020

Tuesday afternoon and evening, the low is expected to weaken further. A low risk of thunderstorms remains east and north of East Cape. No thunderstorms or significant convection expected elsewhere.



Severe Thunderstorm Criteria

In New Zealand, MetService classifies a thunderstorm as severe if one or more of the following criteria are met:

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.