Unstable Period - 17th - 20th Jan

[GreggWard]

Thunder and lightning for the last 10mins from a storm just to the NE of Marton (Work). The storm is now currently over Marton, with thunder every 30 - 40 seconds or so.

[littleheaven]

Heavy bursts of rain in Parnell currently. Dewpoint around 20-21C again today!

Just had a brief heavy downpour around 2.45pm in Glenfield. Now dry again but still very humid. Dewpoint 20.4 and temp 23.2.

[Thunder081]

Well metservice has issued a rare severe thunderstorm watch for wellington, I'd be surprised if the wellington cbd area and south copped any thunderstorms.

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Issued by MetService at 04:09 pm Monday 18 January 2016
Valid until Midnight Monday 18 January 2016
This watch affects people in the following weather forecast districts:
Waitomo
Taumarunui
Taranaki
Manawatu
Kapiti-Horowhenua
Wellington
Marlborough
Nelson
Buller

A very unstable warm moist airmass lies over the west and south of the North Island and the upper South Island. Scattered thunderstorms are occurring or are expected to occur in these areas ahead of a front that will move across these areas this evening.

Some thunderstorms may become SEVERE with local rainfall rates of 30 to 50mm/hr possible. Rainfall of this intensity 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.

In addition, there is a low risk of a coastal tornado about western and northern parts of Taranaki later this evening. Small tornados may cause some structural damage, including damage to trees and power lines, and make driving hazardous. If any tornados occur, they will only affect very localised areas.

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 listen for possible Severe Thunderstorm Warnings.

[Razor]

Radar certainly looks nasty heading down through Horowhenua. Kapiti Coast in the firing line shortly I'd say

[Thunder081]

It's starting to appear in the HQ wellington radar, it even has a little bit of pink!

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[GraemeWi]

I'm sure I can hear some thunder in west Auckland, though there isn't near activity showing on the trackers, a few red spots on the radar off the coast... hmmm...

[spwill]

A few Thundestorms have been occurring offshore from the Auckland west coast on the front, some brief showers here mid afternoon, dewpoint 21C. A gusty northeast wind here so there should be some good convergence on the front.

[GreggWard]

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SEVERE THUNDERSTORM WARNING
TOP PRIORITY FOR IMMEDIATE BROADCAST

Issued by MetService at 05:19 pm Monday 18 January 2016.
Valid until 06:07 pm Monday 18 January 2016.

This warning affects people in the following local government areas:
UPPER HUTT CITY, HUTT CITY, PORIRUA CITY and WELLINGTON CITY.

At 05:07 pm, MetService weather radar detected severe thunderstorms near OFFSHORE MANA ISLAND, PORIRUA, PAEKAKARIKI and PUKERUA BAY.

These severe thunderstorms are moving towards the southwest, and are expected to lie near WELLINGTON at 05:37 pm and near OFFSHORE WELLINGTON SOUTH COAST at 06:07 pm.

These thunderstorms are expected to be accompanied by very heavy rain and damaging wind gusts.

Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.

Very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.

A Severe Thunderstorm Watch remains in force for BULLER, KAPITI-HOROWHENUA, MANAWATU, MARLBOROUGH, NELSON, TARANAKI and WELLINGTON.

The Ministry of Civil Defence and Emergency Management advises that as storms approach you should:
- Take shelter, preferably indoors away from windows;
- Avoid sheltering under trees, if outside;
- Move cars under cover or away from trees;
- Secure any loose objects around your property;
- Check that drains and gutters are clear;
- Be ready to slow down or stop, if driving.
During and after the storm, you should also:
- Beware of fallen trees and power lines;
- Avoid streams and drains as you may be swept away in flash flooding.

This warning is due to be updated or lifted by 06:07 pm Monday 18 January 2016.

[Rogue]

Fantastic storm, plenty of great photos on social media - sometimes it pays just to stay put at home ><. Chased it from Waikawa Beach to Raumati, it overtook me very quickly and by Otaki I was stuck in heavy rain and slow traffic. Saw some great cloud lowerings that kept my imagination alive, and heaps of lightning including some very close CG's. Got this one handheld from inside the car, a technique I mastered on the first day of our 2015 USA chase (and never bothered to try again)

[GreggWard]

Nice photos Rogue.

[Rogue]

There was also this suspicious looking thing tracking along the coast

[Thunder081]

Wellington central did get the thunderstorm after all, we hardly ever get them from the north

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[KiwiWeather]

Great pic's Rogue. I guess the journey in slow traffic was well worth the chase

[kiwisk8er]

The thunderstorm was awesome, I didn't need to chase it, it came to our house. Got some great video of the front coming over.

[03Stormchaser]

Top stuff Rogue, brushing up on those skills before May!

[Richard]

Yes well done Gregg and Roque, hoping its my turn tomorrow.

[RWood]

Very little precip. in Wellington (only 7mm to 8pm) and a few claps of thunder, very little wind after a warm sultry day. According to the trashy tabloid reporting in Stuff, it was something else entirely.

[BeaconHill]

The line of the storm from had lost its energy by the time it got to the airport. There were 3 distant claps of thunder, and a reasonable shower of rain, but nothing out of the ordinary. What was amazing was the sea fog was sneaking in over the hills on the south coast still as the front arrived. I wonder if the cooler air of the southerly undercutting the front helped to "diffuse it"?

[Tornado Tim]

The front has seemed to turn to custard here, seems unlikely to get a storm tonight now, but I am hoping that I will be proven wrong.

[NZstorm]

The line of the storm from had lost its energy by the time it got to the airport. There were 3 distant claps of thunder, and a reasonable shower of rain, but nothing out of the ordinary. What was amazing was the sea fog was sneaking in over the hills on the south coast still as the front arrived. I wonder if the cooler air of the southerly undercutting the front helped to "diffuse it"?

Its a warm upper air set up so yes, the cooler air would have zero CAPE.

The front has seemed to turn to custard here, seems unlikely to get a storm tonight now, but I am hoping that I will be proven wrong.

The system has had a poor history at producing lightning. I am assuming a lack of divergence aloft over the upper NI is a problem.

[spwill]

Torrential shower here just now with the front just about through

[Thunder081]

Very little precip. in Wellington (only 7mm to 8pm) and a few claps of thunder, very little wind after a warm sultry day. According to the trashy tabloid reporting in Stuff, it was something else entirely.

Agreed, stuff is saying things like 'Violent storms' they must've already forgotten about the June 2013 storm or the thunderstorms on the 20th of August 2012 and 20th of September 2013 or they don't actually know what a storm is. I was at Mt Victoria at time, there was little wind, about 5 thunder claps and heavy rain for about 10 minutes.

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[Thunder]

Nice pics!

[mikestormchaser]

Awesome to see the pics!

[NZstorm]

Yesterdays Levin/Wellington storm formed a liner structure ( squall line) so perhaps a severe gust was possible. The problem for a warning system is avoiding false alarms, which is almost impossible. NZ severe thunderstorms tend to be very isolated and hard to predict.

Grey Lynn recorded 16mm yesterday. Fine looking morning.