T-storms risk - Sat 22 Nov

[Razor]

Actually not entirely true spwill while it has been southerly for a couple of hours it seems the action lies to the south still and out to sea

[MoorfNZ]

All change here nr Sheffield... cold wind arrived, strengthening, temp dropped..

[Orion]

Raining here at present.

[NZstorm]

Actually not entirely true spwill while it has been southerly for a couple of hours it seems the action lies to the south still and out to sea

Its all elevated convection though, no surface based storms today. The elevated storms don't produce severe weather.

[MoorfNZ]

Has started to spit in Sheffield.

[Powermad]

MS just lifted their severe thunderstorm warning..

[Tornado Tim]

MS just lifted their severe thunderstorm warning..

The Watch you mean....

[spwill]

Actually not entirely true spwill while it has been southerly for a couple of hours it seems the action lies to the south still and out to sea

But the Metservice severe watch was with the southerly wind change and they still have the severe thunderstorm watch up for Christchurch.
Edit watch lifted now

[MoorfNZ]

MS just lifted their severe thunderstorm warning..

Can't find it on their site - got a link?

EDIT: Got it

[Powermad]

Nope.. coz its gone!

[MoorfNZ]

Nope.. coz its gone!

http://www.metservice.com/warnings/seve ... m-warnings

[MoorfNZ]

WEIRD... it's changed again - above link said no ts action for, basically, all radar areas... now it's changed again

[Nev]

As Tim said, it was never a 'Warning', just a 'Watch'.
Below is an copy of their last update (first issued at 08:40am), then cancelled at 4:25pm this arvo...

MetService - Severe Thunderstorm Watch

Valid to: 5:30pm Saturday 22 Nov 2014
Issued at: 1:02pm Saturday 22 Nov 2014

MetService Severe T-storm Watch Chart- Is. Nov 22, 1.02pm.png

SEVERE THUNDERSTORM WATCH

Issued by MetService at 01:02 pm Saturday 22 November 2014
Valid until 05:30 pm Saturday 22 November 2014
This watch affects people in the following weather forecast districts:
Christchurch
Canterbury Plains
Canterbury High Country

A very strong and active southerly change moves northwards through Mid and North Canterbury this afternoon, bringing squally showers and possible thunderstorms from about Ashburton northwards. There is a moderate risk of a few SEVERE THUNDERSTORMS with this southerly change across the Canterbury coast and Plains, and about the foothills. These storms may produce large hail in excess of 20mm, damaging wind gusts in excess of 110km/h, and the chance of a small tornado inland. Behind the southerly change, thunderstorm activity will quickly ease. Wind gusts of this strength can cause some structural damage, including trees and power lines, and may make driving hazardous. Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, as well as make driving conditions hazardous. 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.

Issued by: gullery

This watch will be updated by: 05:00 pm Saturday 22 November 2014

[NZ Thunderstorm Soc]

Well it's all over now guys.
Don't forget it's called a Thunderstorm RISK" not a Thunderstorm Actual, so no matter how high the risk is, it doesn't mean it would actually happen anyway, but never mind.
In situations like this and considering the EL Nino spring we are having, one has to be cautious and it is better to be safe than sorry.

[Chris Raine]

Found a thunderstorm just north of Geraldine about 2pm ,Heavy rain hail and a flash and clap of thunder three seconds after, almost on top of me as I drove south on the inland road. Yes the southerly change about 25kms ahead of the storm

[NZ Thunderstorm Soc]

The NE or ENE is quite feisty today. Shame it didn't kick in yesterday

[NZstorm]

I did a study of Saturdays set up and the level of free convection was very high at 2000m. It would have been very hard for southerly convergence to push a parcel that high, especially with the surface moisture starting to mix out by early afternoon.

Is there a past case where thunderstorms developed in a westerly over Canterbury? (excluding elevated)

[cantygal]

Well it's all over now guys.
Don't forget it's called a Thunderstorm RISK" not a Thunderstorm Actual, so no matter how high the risk is, it doesn't mean it would actually happen anyway, but never mind.
In situations like this and considering the EL Nino spring we are having, one has to be cautious and it is better to be safe than sorry.

I heard on the forecast though that it was more than a risk. It was basically a definite with 110km/hr gusts from the south with thunder and hail. A big fail in my books but not unhappy it didn't eventuate

[Nev]

I heard on the forecast though that it was more than a risk. It was basically a definite with 110km/hr gusts from the south with thunder and hail. A big fail in my books but not unhappy it didn't eventuate

MetService did have a Warning out for gusts up to 110 km/h in some areas, but it never included thunderstorms and hail. The latter was only mentioned in their Watches and Outlooks.

[cantygal]

MetService did have a Warning out for gusts up to 110 km/h in some areas, but it never included thunderstorms and hail. The latter was only mentioned in their Watches and Outlooks.

Sadly I heard it on 3 different radio stations with the MetService forecast mentioned each time. Thunderstorms and hail were the main elements as was the southerly of 110km/hr.

These weren't read as watches or warnings but their usual hourly city/regional forecasts.

I was also surprised by their lack of accuracy but hey nobody is perfect!

[Dale]

These weren't read as watches or warnings but their usual hourly city/regional forecasts.

There is the problem. One word, beginning with "M".. and no, not metservice

[melja]

I often here on Radio live them reading out watches and warnings and the thing that strikes me as odd is when there is a heavy rain warning for the Canterbury head waters they say its also for the plains and Chch city.

[Nev]

That's the media for ya!

MS's Severe Thunderstorm Watch above uses words like 'possible', 'may', 'chance', 'moderate risk', etc. (note that their earlier T-storm Watch included more southern areas - north of about Timaru, as per the morning Outlook posted at the start of this thread).

Btw, I found their Severe Weather Warning and Severe Weather Watch issued on Saturday morning, which is way too long to post here, but below are the relevant bits…

MetService - Severe Weather Warnings

SEVERE WEATHER WARNING.

ISSUED BY MetService AT 9:10 am 22-Nov-2014

Further heavy rain for the the west of the South Island, the Alps and lower North Island. Northwest gales for central New Zealand.

A front over Fiordland and Southland is moving northwards during Saturday.

This front is preceded heavy rain in the west of the South Island, and also brings a burst of heavy rain to the lower North Island today (Saturday). Heavy falls are still expected in Fiordland till around midday, and in Westland, Buller and about the Main Divide into the afternoon. This includes spillover into the Canterbury headwaters. Streams and rivers are likely to remain in flood, and surface flooding and slips are also possible.

Additionally, strong northwesterlies ahead of the front will affect areas between Canterbury and Hawkes Bay, with severe gales expected in some places. The strongest winds are likely to affect Wairarapa, the hills of Wellington (including the Rimutaka Hill Road) and the Marlborough Sounds. In these areas, gusts of 120km/h or more are possible, which may damage trees, powerlines and can make driving difficult.
...

MetService - Severe Weather Watch

Valid to 9:33am Sunday 23 Nov 2014

SEVERE WEATHER WATCH FOR SOUTHLAND, OTAGO, CANTERBURY, MARLBOROUGH, NELSON, WELLINGTON, HAWKES BAY, TARANAKI

ISSUED BY METSERVICE AT 0933hrs 22-Nov-2014

NORTHWEST GALES FOR CENTRAL AND EASTERN AREAS INTO SATURDAY. HEAVY RAIN FOR OTAGO HEADWATERS, ALSO SOUTHLAND AND MT TARANAKI ON SATURDAY.

A slow moving front near southern Fiordland is forecast to move northwards on Saturday, bringing heavy rain and northwest gales to some areas. Behind the front, a low is expected to deepen just east of Canterbury, resulting in a risk of severe southwest gales about Banks Peninsula, while a rainband moves over the lower South Island.

Warnings remain in force for a number of regions today. This Watch covers a threat of severe weather in other districts as follows:
…

STRONG WIND

CANTERBURY: Northwest gales have eased about the High Country and inland areas north of the Rakaia River, but there is a risk of severe southwest gales about Banks Peninsula Saturday afternoon and early evening.

P.S. Having said that, MS would appear to have been overly optimistic with that T-Storm Outlook and Watch. I think NZstorm, not surprisingly, was more on the money right from the outset…

[melja]

Haha yes i often go by what he is saying and i would think hes well on the money most of the time.

[cantygal]

A friend of mine is in the media and she just gave me the forecast they received from MetService on Saturday at her workplace.

Forecast for Christchurch City-11.08am Sat Nov 22

Strong southerlies, gusting 110km/hr developing this afternoon with hail and thunderstorms also developing. A high of 27.Conditions easing this evening. Low 3.

I don't blame the hosts for reading what they are given when it's worded like that.

She mentioned she did have a watch to read as well.