Low pressure system 18/19 July

Razor · Unread post by **Razor** » Wed 15/07/2015 09:52

Have separated out to new thread as we are getting close enough to this event looking like being of note

Hmmm, a fairly vigorous looking system on Saturday- one to watch now its getting closer.

Bradley · Unread post by **Bradley** » Wed 15/07/2015 10:37

I;m seeing the precipitation numbers increasing day by day for this one Razor - do you agree?

Razor · Unread post by **Razor** » Wed 15/07/2015 11:20

Bradley wrote:I;m seeing the precipitation numbers increasing day by day for this one Razor - do you agree?

Going by GFS its getting more significant as we get closer- a little volatile these types of systems though as to where they cross the country. I'm heading for a long weekend at Lake Brunner this weekend, could be in the firing line

matttbs · Unread post by **matttbs** » Wed 15/07/2015 12:26

Is it me or am I currently seeing a repeat of the june event ie warm advective? Metvuw has the low crossing the South Island and the southerly collides with it right over Canterbury. Definitely one to watch

Razor · Unread post by **Razor** » Wed 15/07/2015 12:37

For later reference...

matttbs · Unread post by **matttbs** » Wed 15/07/2015 13:27

Metservice already onto it with their rural and town forecasts, sleety showers and low level snow for sat/sun. Be interesting to see what their outlook says.

Bradley · Unread post by **Bradley** » Wed 15/07/2015 13:39

North Canterbury is right in the firing line with this one, I see towns like Hanmer Springs getting a quite substantial dump with this system...

RichyDunedin · Unread post by **RichyDunedin** » Wed 15/07/2015 17:50

I'm going to be up in Tekapo over the weekend, hoping to go up the Hooker Lake track at Mt Cook Saturday arvo without getting stuck there.

Bradley · Unread post by **Bradley** » Wed 15/07/2015 17:59

For once WeatherWatch may actually be onto something from an early stage:

http://www.weatherwatch.co.nz/content/w ... ake-note-0

SnwAddct · Unread post by **SnwAddct** » Wed 15/07/2015 18:14

Bradley wrote:For once WeatherWatch may actually be onto something from an early stage:

http://www.weatherwatch.co.nz/content/w ... ake-note-0

I was just going to say they've put out bout 4 articles today regarding this weekend. Maybe in an attempt to make up for their lack of forecasting on the last couple systems..

Bradley · Unread post by **Bradley** » Wed 15/07/2015 18:30

SnwAddct wrote:
Bradley wrote:For once WeatherWatch may actually be onto something from an early stage:

http://www.weatherwatch.co.nz/content/w ... ake-note-0
I was just going to say they've put out bout 4 articles today regarding this weekend. Maybe in an attempt to make up for their lack of forecasting on the last couple systems..

Yes I still laugh when I remember their 'not a significant event' forecast for last weeks system lol

Razor · Unread post by **Razor** » Wed 15/07/2015 20:09

Bradley wrote:For once WeatherWatch may actually be onto something from an early stage:

http://www.weatherwatch.co.nz/content/w ... ake-note-0

To be fair they are somewhat Auckland based, in comparison to CWU for eg... but yes lets keep this on topic, this could be a significant event if it holds to current patterns. School holidays could finish with quite a bang for some.

Bradley · Unread post by **Bradley** » Wed 15/07/2015 20:18

EC's latest model run still wants nothing to do with this, it doesn't even forecast anymore then 20mm for places like Waiouru on the desert road which should get anywhere from 50-100mm out of the system. EC performed very poorly 3-5days out from last weeks system and it seems to be doing it again with this system...

TonyT · Unread post by **TonyT** » Wed 15/07/2015 20:51

Bradley wrote: EC performed very poorly 3-5days out from last weeks system

I disagree. It was poor 7-8 days out, but so was the GFS. By 3-5 days out the EC was very close to the final outcome.

Bradley wrote: and it seems to be doing it again with this system...

How can you possibly know?

petem8nz · Unread post by **petem8nz** » Wed 15/07/2015 20:54

I have found weatherwatch to be quite reliable when it comes to warm advection events.

NZstorm · Unread post by **NZstorm** » Wed 15/07/2015 21:07

This system will be a strong one so some places will feel the effects.

Mid to north Canterbury looking the sweet spot for snow on the current GFS.

Bradley · Unread post by **Bradley** » Wed 15/07/2015 21:34

Bradley wrote: EC performed very poorly 3-5days out from last weeks system

[/quote]

TonyT wrote:I disagree. It was poor 7-8 days out, but so was the GFS. By 3-5 days out the EC was very close to the final outcome.

I hate to prove the expert wrong but you can clearly see from the below output by GFS 7 days before the event it got the precipitation amount right to within a few mm and further runs leading up to the event were also consistent with this - same could not be said for EC which wildly exaggerated moisture levels 5 days out which is why I'm guessing you put your Snow Watch out at the time but later changed it

Storm Struck · Unread post by **Storm Struck** » Thu 16/07/2015 00:11

Do we know if the polar vortex is still lingering? I don't really know much about it or how long it can potentially stick around for but it did bring very low level snow to NSW the other day.
This could increase chances of a decent event at all levels, but those two systems are colliding in the right spot at the moment.
Its very hard to forecast advective snow as not many models pick it up, I do like the low 850 temps in conjunction with the set up of this event however there's so much more to come right than just one model.
It would be good to go back on data from June 12th 2006 to see what we can match.
Im not getting too excited just yet but it does look like a humdinger system

NZstorm · Unread post by **NZstorm** » Thu 16/07/2015 06:43

Jetstream pattern for Saturday. This is looking like a text book warm advective snow scenario for Otago/Canterbury, with eastern Tasman low pressure development occuring between a polar jet over the South Island and subtropical jet in north Tasman.

Bradley · Unread post by **Bradley** » Thu 16/07/2015 07:08

Storm Struck wrote:Do we know if the polar vortex is still lingering? I don't really know much about it or how long it can potentially stick around for but it did bring very low level snow to NSW the other day.
This could increase chances of a decent event at all levels, but those two systems are colliding in the right spot at the moment.
Its very hard to forecast advective snow as not many models pick it up, I do like the low 850 temps in conjunction with the set up of this event however there's so much more to come right than just one model.
It would be good to go back on data from June 12th 2006 to see what we can match.
Im not getting too excited just yet but it does look like a humdinger system

Here is the GFS output from the day before 12th June 2006 event mate

Bradley · Unread post by **Bradley** » Thu 16/07/2015 07:16

TonyT wrote:
Bradley wrote: EC performed very poorly 3-5days out from last weeks system
I disagree. It was poor 7-8 days out, but so was the GFS. By 3-5 days out the EC was very close to the final outcome.

Bradley wrote: and it seems to be doing it again with this system...
How can you possibly know?

You honestly think Christchurch will only get 5mm out of this event like EC is forecasting?

jamie · Unread post by **jamie** » Thu 16/07/2015 07:17

How do people think the north Island will go?

NZstorm · Unread post by **NZstorm** » Thu 16/07/2015 07:22

This system is progged to move through quickly which will at least reduce its impact.

Central North Island will catch some snow showers in the colder air as the low moves away.

Richard · Unread post by **Richard** » Thu 16/07/2015 07:28

Three snowfalls in one winter hasn't happened here in the last 15 years and there's still another two months in which more falls could happen

hozza95 · Unread post by **hozza95** » Thu 16/07/2015 08:43

We are already at 6 snows here this year here which would be the most already in atleast 10 years, even in gore which is 50m they have already had 4 which is more then their average of 2-3. Crazy thing is we are only just now entering the months where probably 80% of our snowfalls happen each year , so 10+ snows this year for us isn't out of the question

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