Storms NE SI & Eastern NI 12/12/2016

[Richard]

Valid to: Midnight Monday 12 Dec 2016

Issued at: 9:11am Monday 12 Dec 2016

A trough is crossing the north of the North Island this morning. A front over northern Canterbury is expected to move onto the southern North Island around midday and reach Gisborne this evening.

There is a low risk of thunderstorms over Northland and northern Auckland this morning associated with the trough.

There is a moderate risk of thunderstorms associated with the front for northern Canterbury and the Kaikoura Coast this morning, Wellington, Kapiti, eastern Manawatu, Wairarapa and coastal Central Hawkes Bay this afternoon. These thunderstorms may bring localised heavy rain with intensities of 10 to 25mm per hour and hail of 5 to 20mm diameter. For the Kaikoura Coast and Wellington there is also the possibility of strong wind gusts of around 90 km/h. About the Canterbury Foothills and Kaikoura the moderate risk of thunderstorms continues into the afternoon. About northern Wairarapa there is also a low risk that one or two thunderstorms could be SEVERE with downpours of 25 to 35mm per hour and large hail.

About Gisborne, northern Hawkes Bay and inland Central Hawkes Bay sea breezes and afternoon heating are likely to create convection before the front arrives. There is a moderate risk of thunderstorms in these areas during the afternoon and evening. These thunderstorms could have localised heavy rain with intensities of 10 to 25mm per hour and hail of 5 to 20mm in diameter.

Cold air aloft is expected to move over the north of the South Island during the afternoon and for much of Marlborough away from the Kaikoura Coast and eastern Nelson there is a high risk of thunderstorms and a moderate risk that some may be SEVERE. The thunderstorms are likely to be accompanied by localised heavy rain and hail, with downpours of 25 to 35mm per hour and large hail in SEVERE thunderstorms.

Outside these moderate and high risk areas there is a low risk of thunderstorms as shown on the chart.

[Richard]

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[TonyT]

When the change came through here about 7.45am there were a few hailstones and some interesting twisted cloud forms. I thought at the time, if this had been 5pm in the evening then we would have had some thunder and heavy hail with it.

[mikestormchaser]

Still though with daytime heating we could get a few heavy showers/ hail develop about. Given 500mb temp -28 and 700mb -9 and time of year it is.there is a wee bit of surface moisture on the models throughout today

[Bradley]

57mm here in the last 24 hours, setup now for the next 2-3 weeks even with no further rain in that time

[Richard]

57mm here in the last 24 hours, setup now for the next 2-3 weeks even with no further rain in that time

Good amount 0.6mm here, nothing this morning......so far

[Bradley]

57mm here in the last 24 hours, setup now for the next 2-3 weeks even with no further rain in that time

Good amount 0.6mm here, nothing this morning......so far

Hope you get something out of this system Richard, even 5-10mm would be most welcome I'm assuming

[Orion]

A peal of thunder heard here a few moments ago

[Richard]

Good amount 0.6mm here, nothing this morning......so far

Hope you get something out of this system Richard, even 5-10mm would be most welcome I'm assuming

Would be handy.

A line of heavy showers have developed inland from Ashburton.

[Richard]

Just had a heavy shower, bit of hail with three claps of thunder, round two not far off.

[NZ Thunderstorm Soc]

We had a thunderstorm here in West Melton @ 7am this morning, with 3 elongated peals of thunder and very heavy rain.
A bit of a surprise. 44.5mm of rain all up so far, yesterday and today.

[Thunder081]

Guys when the southerly front moved over Wellington harbor there was rotation on the water in this video. Do you guys think this is a waterspout forming or a large whirlwind: https://vimeo.com/195244448

[melja]

80mm here in the first 12 days of the month so bloody astonishing for December.

Sent from my Lenovo K50a40 using Tapatalk

[mikestormchaser]

Guys when the southerly front moved over Wellington harbor there was rotation on the water in this video. Do you guys think this is a waterspout forming or a large whirlwind: https://vimeo.com/195244448

That's really interesting!! Looks of some type of rotation anyway!!

[NZ Thunderstorm Soc]

Guys when the southerly front moved over Wellington harbour there was rotation on the water in this video. Do you guys think this is a waterspout forming or a large whirlwind: https://vimeo.com/195244448

I had a thunder potential for this out last week and this seems to been fruitful even though I had my doubts yesterday. I think the potential for thunderstorm dwindled away from the severe thunderstorm activity that Met Service forecasted to what we had today.
I get excited at the forecast of a 'Disturbed SW flow " at this time of year because I know something may happen. Nice coverage of the rotation in the water which could of lead to a waterspout but obviously the atmosphere above didn't deliver.

[mikestormchaser]

Lots of polar troughs hinting at us in the models John. All of a sudden Thursday sticks out now. I won't believe it until couple days out!

[Thunder081]

Cheers guys, after looking at my timelapse footage this was not the start of a waterspout but a big whirlwind caused by what looks like to be winds from the front coming from Oriential and Evans Bay and then clashing at Point Jerningham at the right angle.

Here's the timelapse: https://vimeo.com/195292284

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