Low pressure system 18/19 July

[Razor]

Metservice going large on this with watch out for a major snowfall

[Bradley]

Yep they are going by what all the other models are saying except EC - this is their forecast for Saturday/Sunday for the plains:

A period of rain, followed by showers. Snow possibly lowering to 100 metres in the afternoon or evening, and to near sea level overnight. Winds changing strong southerly, possibly gale about Banks Peninsula.

[TonyT]

Not too different from other forecasts. Snow on the beach in Kaikoura Sunday morning perhaps?

[SnwAddct]

Issued: 2:46pm Thursday 16 Jul 2015
Valid from Saturday 18 July 2015 to Tuesday 21 July 2015

A complex low is expected to pass east over the centre of the country during Saturday and Sunday, while a strong cold southerly spreads north. This is a complex situation with snow expected about eastern parts of the South Island and the lower North Island, also areas of heavy rain about the North Island and upper South Island, with southerly gales about central areas, especially affecting Wellington. At this stage there is a degree of uncertainty as to the amounts and location of the heaviest of the rain and snow, however, there is a moderate risk of heavy snow about Fiordland, Southland, Otago and Canterbury and a Watch is now in force. In addition, there is a low risk of heavy snow about Marlborough, Wellington, Wairarapa (including the Tararua District), and the central North Island high country from late Saturday to Sunday, with a low risk of heavy rain for much of the North Island and the Marlborough Sounds, excluding Gisborne and northern Hawkes Bay. Cold southerly gales are expected to spread over the country during Saturday and Sunday, with a low risk of severe gales about Westland, Banks Peninsula, Marlborough Sounds, Wellington, Wairarapa, Kapiti/Horowhenua, Manawatu and Taranaki.

People are advised to stay up to date with the latest forecasts and warnings as we approach this event.

Southerlies and showers persist over the country during Monday, then finally ease on Tuesday with the temperatures slowly rising. However, severe frosts are likely about the South Island from early next week, with black ice possible on the roads.

[Nev]

^ Might pay to say whether the above is a Warning, Watch or Outlook?

Here's the accompanying map for that 'Severe Weather Outlook' from MS…

MetService Severe WX Outlook map Is. July 16, 2.46pm.png

[Bradley]

So much is going to change with this system in the next 48 hours - will be a very interesting one to watch unfold

[Bradley]

EC now going for a grand total of 3.7mm for the whole event for Christchurch

[NZstorm]

EC now going for a grand total of 3.7mm for the whole event for Christchurch

Are you referring to the European model Bradley?

[Bradley]

Yep sure am - http://m.yr.no/place/New_Zealand/Canter ... /long.html

[mikestormchaser]

Bsch gfs suggests coldest air moving in from 9pm tomorrow night around Canterbury with moisture levels dropping away around midnight. As the low moves away opening up a more frigid SW gate and coastal chain showers. I think best chance for snow in city will be from 10pm so my forcarst would be for rain setting in from midday with snow lowering to 300m during the afternoon. Rain easing in the evening followed by showers with snow lowering to near sea level overnight. Strong SW picking up

[Bradley]

Metservice seem to be spot on with their latest warning, they are going for 10-15cm down to the 300-400m mark for Canterbury...

[Orion]

Metservice seem to be spot on with their latest warning, they are going for 10-15cm down to the 300-400m mark for Canterbury...

What they are saying is:
"Snow is expected to start accumulating from late Saturday morning or early afternoon. In the 6 to 9 hours from 3pm Saturday, 10 to 15cm is likely to accumulate above 400 metres."

[Razor]

Glorious at cave Stream Reserve this morning

[SnwAddct]

Metservice going for a total of 80+ cm of snow up at Ruapehu from Saturday lunchtime to Sunday evening.. The bulk of that seems to fall when the freezing levels is down around 700m so could be another interesting couple of days for Central/Lower North Island..

[NZstorm]

Glorious at cave Stream Reserve this morning

Awesome photo Razor.

[Tornado Tim]

Yep sure am - http://m.yr.no/place/New_Zealand/Canter ... /long.html

YR.no is not the ECMWF (ECMWF by in large part is not free) - it only uses a bit of its model data in part. The Norwegian Meteorological Institute (yr.no) run there own models. And may or may not be attributed by model output obtained from the ECMWF.
More Info http://om.yr.no/info/fakta/

[TonyT]

Yep sure am - http://m.yr.no/place/New_Zealand/Canter ... /long.html

YR.no is not the ECMWF (ECMWF by in large part is not free) - it only uses a bit of its model data in part. The Norwegian Meteorological Institute (yr.no) run there own models. And may or may not be attributed by model output obtained from the ECMWF.
More Info http://om.yr.no/info/fakta/

And yet,
http://om.yr.no/forklaring/forsta-varslene/
when run through Google Translate says:
"Forecasts for Northern Europe are more frequently updated than the other alerts (which comes from the European meteorological center ECMWF)."

[Richard]

I see now the MS have Hanmer Springs with 59mm which would mean about 1/2 m of snow

[Bradley]

I see now the MS have Hanmer Springs with 59mm which would mean about 1/2 m of snow

With 41mm of that falling from midday Richard so you'd think at least half of that will be snow...what elevation are you mate?

[NZ Thunderstorm Soc]

Glorious at cave Stream Reserve this morning

Nice picture
I like the western side line of the Torlesse Range in that photo, with a reverse of the "The Face".

[Manukau heads obs]

the tasman low is looking impressive already on the sat image
huge moisture feed from the sub tropics developing
wind has gone NNE here already

[Richard]

With 41mm of that falling from midday Richard so you'd think at least half of that will be snow...what elevation are you mate?

We are at 243m, about the same as Oxford

[Dean.]

I'm surprised Tony hasn't mentioned a heavy snow chance in his forecast for inland areas...moisture levels seem to be up there for 6-12 hours.

[Bradley]

I'm surprised Tony hasn't mentioned a heavy snow chance in his forecast for inland areas...moisture levels seem to be up there for 6-12 hours.

He has stuck to his guns for the entire lead up to this event with 5-10cm above 200m, we will see I guess!

[Bradley]

With 41mm of that falling from midday Richard so you'd think at least half of that will be snow...what elevation are you mate?

We are at 243m, about the same as Oxford

You should do quite well out of this event Richard, prob around 15cm going by the models at the moment