Severe Weather Outlook

Valid from Monday 14-Jun-2021 to Thursday 17-Jun-2021

Issued: 2:56pm Saturday 12 Jun 2021

A trough is expected to move over the North Island on Monday before moving away to the east on Tuesday, followed by a slow moving complex low over New Zealand until Thursday.

There is low confidence of warning amounts of rain for Mount Taranaki on Monday, and for Northland on Monday and Tuesday. Meanwhile, there is moderate confidence rainfall accumulations with reach warning criteria about eastern Bay of Plenty on Monday and Tuesday, mainly about the ranges.

There is also low confidence that rainfall may approach warning amounts about Westland south of Otira and Fiordland north of Doubtful Sound on Tuesday.

Lastly, there is low confidence that easterlies will bring warnable amounts of rain to eastern Otago on Monday and Wednesday.

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 Sunday, 13-Jun-2021

Issued: 7:42am Sunday 13 Jun 2021

A trough in the Tasman Sea and associated rain-bands are expected to move onto western parts of central and southern New Zealand late today. Severe Weather Watches and Warnings for heavy rain have been issued for northern and western parts of the South Island. As indicated on the chart, there are low risk of thunderstorms embedded within broader areas of rain about Fiordland from afternoon, about Westland and Buller from this evening, and about North Taranaki tonight. If any thunderstorms do occur they are probably more likely offshore and will boost local rainfall rates. No other thunderstorms or significant convection expected over New Zealand today.



Valid to Noon Monday, 14-Jun-2021

Issued: 9:11am Sunday 13 Jun 2021

A moist northerly flow will cover the North Island on Monday morning with embedded fronts bringing rain to many northern and western areas. A weak trough covers the South Island. In the North Island, there is a moderate risk of a few thunderstorms about northern Northland mid to late morning, and a low risk covering other parts of Northland and western areas from Waikato to Taranaki. In the South Island, there is a low risk of a few thunderstorms about western areas from Kahurangi National Park to northern Fiordland before dawn. Any thunderstorms that occur will be accompanied by localised heavy rain. No other thunderstorms or significant convection expected over New Zealand on Monday morning.



Valid to Midnight Monday, 14-Jun-2021

Issued: 9:43am Sunday 13 Jun 2021

A moist northerly flow will continue to cover the North Island during the second half of Monday bringing rain or showers to many North Island areas. A front moves onto the South Island from the Tasman Sea during this period. Over the northern and central North Island, there is a broad low risk of thunderstorms from Whanganui, Taihape and eastern Bay of Plenty northwards through the whole period. Over the South Island, there is a moderate risk of thunderstorms about southern Westland and northern/central Fiordland from late afternoon or early evening, with brief heavy rain and small hail. A broader low risk covers other western areas south of Westport, including near the main divide of the the Southern Alps, through the whole period. No other thunderstorms or significant convection expected over New Zealand 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.