Severe Thunderstorm Watch Get File

Severe Thunderstorm Watch

Issued : 9:15am Wednesday 24 Jan 2018

Issued by MetService at 09:15 am Wednesday 24 January 2018Valid until 09:00 pm Wednesday 24 January 2018This watch affects people in the following weather forecast districts:Bay of PlentyTaupoGisborneHawkes Bay

Humid conditions are likely to lead to showers and thunderstorms developing about the northeast of the North Island late morning or this afternoon. One or two of these thunderstorms may become SEVERE after 1pm about eastern areas of Bay of Plenty and Taupo and inland areas of Gisborne and northern Hawkes Bay. Severe Thunderstorms could produce localised downpours with intensities of 25 to 40mm per hour. These thunderstorms should subside this evening.

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.

MetService will continue to monitor the situation closely for severe thunderstorm development and will issue further updates.

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: Allister Gorman

This watch will be updated by: 02:00 pm Wednesday 24 January 2018

Probability/Confidance Map
Valid Till 9:00pm Wednesday 24 Jan 2018

Severe Thunderstorm Criteria

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

Heavy rain (from thunderstoms): 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.

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