Storms Southern and eastern central NZ 4/1/2017

[Richard]

Thunderstorm Outlook issued by the Met Service

Valid to: Midnight Wednesday 4 Jan 2017

Issued at: 10:52am Tuesday 3 Jan 2017

The active front and associated southerly wind change is forecast to cross North Canterbury, Marlborough, eastern Nelson, Wellington and Wairarapa during the afternoon, bringing a period of heavy showers and a moderate risk of thunderstorms. Any thunderstorms that eventuate are likely to produce localised heavy rain up to 15mm per hour, hail of 5 to 15mm in diameter and strong wind gusts around 100 km/h. There is a broader low risk of thunderstorms extending further west and north during the afternoon and evening, as indicated on the chart.

The deep cold air over the lower South Island moves away to the east in the evening. Further heavy, squally showers with small hail are expected about southern Fiordland, Southland, Otago and Canterbury until early evening, with a broad low risk of one or two thunderstorms. This risk of thunderstorms is considered nearer moderate about coastal parts of Southland and Otago during the afternoon. Any thunderstorms that eventuate are likely to produce localised heavy rain, small hail and strong wind gusts of 90 to 110 km/h.

[Tornado Tim]

This sort of polar type troughing is rather unusual this far into the Summer Season, esp with the upper level temps forecast down to -35°C. Will deffo be some Thunder tomorrow with the southerly change going through.
May be a slight chance of storms turning quite squally/severe with isolated gusts perhaps exceeding 110km/hr in exposed places.
Hail is also a good chance with the storms due to the unduly cold upper level temps.

[Richard]

Updated chart

Issued at: 8:56pm Tuesday 3 Jan 2017

Updated at 8:50pm Tuesday - Moderate risk area about southern South Island pushed further north, but northern moderate risk area confined to North Canterbury and the Kaikoura area.

[Richard]

Thanks Tim for you thoughts on tomorrows prospects, at this time of year i much prefer the slow moving heat buildup summer storms, but i wont say no to a fast moving polar tough set up

[NZstorm]

The SW change mid to late morning over the Canterbury plains could develop into a storm although instability is low topped. Need the heating this morning.

Very cold air over the South Island this afternoon looks more like a July polar blast with 700mb temperatures -14C progged for Southland/Otago.

[Richard]

Blue skies here this morning so heating wont be a problem. Before the sun came up there were small pockets of low cloud which was moving up from the south, this has now changed and are heading back south. Conditions are looking favorable.

[Richard]

This mornings update now includes all of eastern Canterbury, coastal Kaikoura and south eastern Wairarapa in the moderate risk area.

Valid to: Midnight Wednesday 4 Jan 2017



Issued at: 8:28am Wednesday 4 Jan 2017

A cold front over the lower South Island this morning is forecast to cross central New Zealand this afternoon and early evening followed by a strong unstable south to southwest flow.

Scattered heavy showers with hail and isolated thunderstorms are expected to spread onto southern and eastern parts of the South Island this morning and afternoon onto the lower North Island late this afternoon and early evening.

There is a moderate risk of isolated thunderstorms about much of Southland, Otago and South Canterbury late this morning and afternoon, and also about Mid and North Canterbury, the Kaikoura area and Wairarapa this afternoon and early evening. A broad low risk covers other parts of the lower North Island, Marlborough, Canterbury, eastern Nelson down to southern Fiordland during the afternoon and evening, as indicated on the chart. These thunderstorms will be accompanied by brief heavy rain, strong squally wind gusts of 90 to 110 km/h and hail of 5 to 15mm diameter.

No thunderstorms or significant convection expected elsewhere.

[mikestormchaser]

Not much I can do today as am up in Nelson until Thursday. I'm not overly convinced on today looking at models anyway just because of the timing of it all but there is some really cold air though!! Hints of cold unstable clouds early up this way this morning.

[Bradley]

Metservice going all out on that latest Thunderstorm outlook that Richard mentioned before, looking more and more promising here with bright sunshine, if we can get up to 17-18C before the change rips through we could be in for a goodie

[03Stormchaser]

Metservice going all out on that latest Thunderstorm outlook that Richard mentioned before, looking more and more promising here with bright sunshine, if we can get up to 17-18C before the change rips through we could be in for a goodie

A mod risk is going all out?? Very cold air coming, southerly buster type scenario.

[Orion]

Southerly and rain in Ashburton for the past thirty minutes.

[Richard]

The first leading edge of cold air closing in, a mild NW wind currently, but thats about to change.

[Orion]

A mere 9deg.C here now

[tich]

Was fine earlier in morning, but cold and wet now in Akaroa, with a fresh southerly.

[Richard]

Thunder heard to the SE

[NZstorm]

Invercargill observed thickness today 528, 700mb -14.3C and 500mb -32.9C. I might look back to see when the last time such cold numbers were recorded in January.

I see the temp in Queenstown at 3pm 10C.

[Richard]

Certainly got cold alright, rain has set quite steadily and the wind has nearly died out

[Chris W]

I see a clearance in the sky, after a grizzly grey afternoon! A short shot at some heating perhaps?

[tich]

Cleared up now in Akaroa, but southerly is now strong and gusty. I see cold change has now hit Wellington, with temps on Metservice obs page about 9-10C about the city and a wintry 5C at summit of Rimutaka Hill. (still above 20C further north in NI where change hasn't yet hit)

[Richard]

Strange weather, winds a light N to NW, should be a southerly

[Richard]

The storm we heard over Waipara way ive heard delivered large hail which may not be good news for the grapes, possibly the saving grace could be that the grapes are still small.

[Nev]

Pic of the hail in Waipara yesterday…

Hail in Waipara by Sandy Paterson ℅ Stuff.jpg

Also moderate hail reported in Dunedin and Queenstown, more than 25 lightning strikes (IC's?) reported in Rangiora and gusts up to 117 km/h recorded at Le Bons Bay…

'Hail pelts Waipara, bypasses Christchurch' - The Press
'Cool change rips through region' - ODT

[Richard]

Spoke to one person last night that said that there willow tree were stripped, so must have been large hail to do that.

[Bradley]

Metservice going all out on that latest Thunderstorm outlook that Richard mentioned before, looking more and more promising here with bright sunshine, if we can get up to 17-18C before the change rips through we could be in for a goodie

A mod risk is going all out?? Very cold air coming, southerly buster type scenario.

Am I allowed to say 'going all out' going by tonorrow's thunderstorm forecast?

[Chris W]

I think so Bradley! Was surprised to see the lightning symbol in the forecast just now and read that outlook, hadn't really looked at tomorrow for storms.