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Severe Thunderstorm Watch

Valid to 10:00pm Thursday 13 Dec 2018
Issued at 8:09am Thursday 13 Dec 2018

SEVERE THUNDERSTORM WATCH

Issued by MetService at 08:09 am Thursday 13 December 2018
Valid until 10:00 pm Thursday 13 December 2018
This watch affects people in the following weather forecast districts:
Waikato
Waitomo
Taumarunui
Bay of Plenty
Rotorua
Taupo
Gisborne
Hawkes Bay
Taihape
Wanganui
Manawatu
Tararua
Kapiti-Horowhenua
Wairarapa
Wellington

There is a risk of SEVERE thunderstorms developing about central parts of the North Island this afternoon and evening, from the Kaimai Range and the ranges of Bay of Plenty and Gisborne down through the central North Island high country to the Tararua Range, producing localised downpours of 25 to 40mm per hour or possibly more, and hail possibly larger than 20mm.

Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.

Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain.

Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, as well as make driving conditions hazardous.

Note: A Severe Thunderstorm Watch means conditions are favourable for severe thunderstorms in and close to the watch area. People in these areas should be on the lookout for threatening weather conditions and monitor for possible Severe Thunderstorm Warnings.

For information on preparing for and keeping safe during a storm, see the Civil Defence Get Ready Get Thru website

Issued by: Sarah Garlick

This watch will be updated by: 10:00 pm Thursday 13 December 2018

map

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.

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.