Lightning strikes 30,000 times and now for tornados

Tuesday, 17 May 2016

Tornados could arrive on Wednesday in the wake of stormy weather that sparked a mass lightning storm sending 30,000 strikes across the country.

Instability in the atmosphere rocked the skies overnight on Monday, sending more than 3000 bolts out in a two-hour period.

A lightning strike Te Rore at 6.15 pm during the lightning storm over Waikato.

The show that boomed overhead was a result of two bursts of activity that prompted severe weather warnings for Auckland, southern Northland, Waikato, Waitomo and further south.

One hit between 6-8pm on Monday and the other front followed from midnight to 2am on Tuesday.

* Lightning strikes more than 3000 times in two hours as wild weather threatens

* Stormy weather keeps emergency services busy in Waikato**

More stormy weather was forecast for Wednesday, with MetService warning of severe thunderstorms with possible tornados from mid-morning.

'A very active front should move quickly across New Zealand during Wednesday and is expected to bring a period of thunderstorms to western areas of the country.'

Squally thunderstorms with gusts greater than 110 kmh and brief intense downpours of 25 to 35mm/hr were forecast for Waikato and Waitomo to the Kapiti Coast.

Tornados were also a possibility from mid-morning to mid-afternoon, Metservice reported.

'If any tornados occur, they will only affect very localised areas. Downpours can cause 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.'

It was a sign summer is over and autumn was here in full force, MetService meteorologist Tom Adams said.

'This rapidly changing weather is very autumnal.

'Every day this week is going to be different from the next.'

WILD NIGHT

At its peak 4000-5000 lightning strikes an hour hit over land and sea on Monday. Hundreds struck over the Waikato alone.

Most of the action came in the first front which kept emergency services busy removing downed trees from roads including in the Karangahake Gorge.

Northern fire communications shift manager Scott Osmond said fire services dealt with a dozen weather calls in the area overnight.

Up to 400 lightning strikes took place over the Waikato region, Adams said.

'Another front behind that brought thunder and lightning overnight from midnight until 2am. Although not as much as the first one, it was enough to keep some people up and brought a fair amount of rain with it.'

Adams said the lightning storm was a result of a strong temperature change combined with a sharp trough of unstable air.

'The reason there was a lot of lightning is the way the temperature was stacked in the atmosphere - it was very unstable.'

When the air shoots rapidly up an air column, hitting ice and water particles in the cloud, it creates a charge separation, he said.

Negative and positive charges bump around in the cloud. When they get big enough, they react, causing a giant spark - lightning.

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