Possible T-storms Otago/Canterbury - Nov 3-5

[mikestormchaser]

Thought it might be an idea to start a thread for this. Some cold upper air moving over the south Island today, with a S change should trigger storms in parts of otago and canterbury. Only killer today could be a NW wind flow.

[Nev]

This morn's update from MS...

MetService - Thunderstorm Outlook

Valid to: Midnight Monday 3 Nov 2014
Issued at: 8:20am Monday 3 Nov 2014

An unstable westerly flow covering central and southern New Zealand today will turn southwest over the South Island during the afternoon and evening as temperatures cool aloft.

Thunderstorms are expected about the South Island west coast through much of the day, especially on the ranges. These thunderstorms should clear from Fiordland towards midday, and from Westland this evening. Localised heavy rain and small hail will accompany the thunderstorms.

In the east of the South Island, a southwest wind change should move north through Otago and South Canterbury this afternoon and reach Mid/North Canterbury in the evening. Isolated thunderstorms are expected to develop on the wind change and possibly in the cold air behind it. Brief heavy rain and hail up to about 15mm diameter can be expected with these thunderstorms.

A broad low risk of thunderstorms covers other parts of the South Island from western Nelson and Kaikoura southwards later today as indicated on the chart.

In the North Island, a cold front moving eastwards across northern and central parts may bring a few thunderstorms about the ranges of eastern Bay of Plenty this afternoon, but this risk of storms is considered low.

No other thunderstorms or significant conveciton expected over New Zealand today.

MetService T-storm Outlook Map - Oct 3.png

[NZstorm]

Day 1 of a 4 day event as the cold upper level system moves across NZ. Low severe hail probs each day.

[Nev]

And tomorrow afternoon's Outlook…

MetService - Thunderstorm Outlook

Valid to: Midnight Tuesday 4 Nov 2014
Issued at: 10:18am Monday 3 Nov 2014

The South Island is expected to be very unstable on Tuesday afternoon and evening due to a combination of light surface winds and very cold temperatures aloft.

Daytime cloud buildups will therefore produce scattered heavy showers and thunderstorms during the afternoon and evening, especially inland.

As indicated on the chart there is a moderate to high risk of thunderstorms extending from Marlborough and Nelson, through inland Westland and Canterbury to northern parts of Fiordland and Otago.

A lower risk covers almost all the remaining South Island (except near the south coast) in the afternoon and evening, and also Wellington, Wairarapa and Central/Southern Hawkes Bay from evening.

These thunderstorms will be slow-moving producing localised heavy rain, hail,and snow about the higher ground. The hail is likely to be significant, with hailstones mostly in the 10-20mm diameter range, but larger hailstones are possible in one or two inland South Island areas. Snow can be expected down to 500-600 metres about inland Canterbury, Westland and Otago.

No other thunderstorms or significant convection expected over New Zealand on Tuesday afternoon and evening.

MetService T-storm Outlook Map - Oct 4, pm.png

[03Stormchaser]

Metty going with a massive high risk area for tomorrow, don't think it will be that widespread. Storm Chasers will be chasing both days.

[jamie]

I'm down in Cromwell from tomorrow thru to Friday and then Queenstown Friday to Wednesday. Hopefully things develop that far south.

[Razor]

very strong NW here still, I would say killing any chance of action today

[03Stormchaser]

Change isn't expected till after 7pm, I expect it to have died off by then

[03Stormchaser]

A couple strikes picked up around oamaru at present

[mikestormchaser]

man thats quickly blowen up!! check out the radar all of a sudden. started offshore and now its onshore and coming up the coast fast!

[Orion]

Wind-change just coming through here now.

[matttbs]

Possible TS in that thin band moving inland toward chch according to the radar. It's quite odd as it's moving in a different direction than the main band even though they are nearly touching on the radar

[Razor]

Looks a fizzer to me

[03Stormchaser]

Followed a weak gust front from about Chertsey to Leeston. No lightning or hail observed.

[NZstorm]

Nice structure photo O3Stormchaser. The 500mb temperature on the line was -29C, goes to show the stabilising effect of that NW.

[03Stormchaser]

Should be improving conditions today. Although at my last look it seems it will be further south, maybe even in the Mackenzie country. Pity BSCH is down at present.

[Nev]

Not too much change to this morn's update for today…

MetService - Thunderstorm Outlook

Valid to: Midnight Tuesday 4 Nov 2014
Issued at: 8:37am Tuesday 4 Nov 2014

Conditions are expected to be very unstable over the South Island today in the presence of a signigicant cold pool aloft. Daytime heating and light winds will combine to produce scattered heavy showers inland this afternoon, with thunderstorms likely over the hills and ranges from Marlborough to Otago,including the Main Divide. Any thunderstorms that develop are forecast to be slow moving producing localised heavy rain and hail. The hail is likely to be significant and may reach 20mm in diameter, with a low risk of severe storms producing larger hail and heavier rain - especially about northern Canterbury and Marlborough.

Over the North Island, a southerly change in Cook Strait this morning is accompanied by heavy showers and the odd thunderstorm which may affect the south coast of Wairarapa this morning. This afternoon however, heavy showers are likely to build throughout inland Wairarapa as winds turn onshore, with a moderate risk of one or two thunderstorms bringing locally heavy rain and hail.

Outside these areas, there is a lower risk of isolated thunderstorms this afternoon and evening from inland Wanganui and Central Hawkes Bay down to Fiordland and eastern Otago.

For the central and upper North Island, convective showers are also likely this afternoon, especially inland from Coromandel through Bay of Plenty to Hawkes Bay.In these areas, a few showers may be heavy with small hail, but thunderstorms are considered unlikely.

MetService T-storm Outlook Map - Oct 4.png

[mikestormchaser]

Low risk severe now hmm.. well I can knock off early today if needed to chase

[jamie]

Awesome! Ill be flying over top of it all. Leaving Auckland at 2.15pm and arrive in Queenstown 4pm.

[Razor]

Some promising bubble ups getting underway already

[Richard]

Havent got a computer at the moment,so posting this form the library on the way back from CHCH,certainly looking good this nearly in the day

[matttbs]

Does anyone know how often we get tornadoes in Canterbury?

[03Stormchaser]

I've seen three in last 18 months, but around 1 a year would be an average I guess.

[Nev]

Havent got a computer at the moment,so posting this form the library on the way back from CHCH,certainly looking good this nearly in the day

Not so much for your garden - you're in the largest hail risk area.

[petem8nz]

Some promising bubble ups getting underway already

Been Watching them all morning and the odd anvil in the distance from time to time out west.