Severe Weather Outlook

Valid from Friday 31-Mar-2023 to Sunday 02-Apr-2023

Issued: 10:16am Wednesday 29 Mar 2023

On Friday, a deep low lies near the Chatham Islands, although it is not depicted on the chart, there is low confidence that easterly winds may reach severe gale at the Chatham Islands during Friday morning.
A ridge should push eastwards across New Zealand on Friday. On Saturday and early Sunday a trough of low pressure is expected to move eastwards across New Zealand, bringing a period of rain or showers to much of the country. There is low confidence of rainfall reaching warning amounts over the southern and central ranges of Westland, and western parts of Tasman, on Saturday. Another ridge is forecast to spread across New Zealand late Sunday and Monday.



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 Thursday, 30-Mar-2023

Issued: 7:12am Thursday 30 Mar 2023

No thunderstorms or significant convection expected during this period.



Valid to Noon Friday, 31-Mar-2023

Issued: 7:13am Thursday 30 Mar 2023

No thunderstorms or significant convection expected during this period.



Valid to Midnight Friday, 31-Mar-2023

Issued: 7:14am Thursday 30 Mar 2023

No thunderstorms or significant convection expected during this period.



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.