Cold Snap Next Week?

ScottyD · Unread post by **ScottyD** » Wed 11/06/2003 13:43

Does it look like next week will be our first real cold snap of the winter? Here's hoping it will bring lots of moisture with it. I've got my season pass for Ruapehu and i'm waiting for the cold to arrive. Heading off on holiday to South Island on 30th June. Hopefully there will be clear weather and lots of snow.

Michael · Unread post by **Michael** » Wed 11/06/2003 14:42

As long as it gives us Southeasterlies in the city-it can rain/snow/sleet in the South Island (They seem to want inclement weather a lot)

Dean. · Unread post by **Dean.** » Wed 11/06/2003 17:36

Mt Hutt was due to open on June 7th,they only have a 5cm base which fell on Monday night plus the snowmaking last night.My season pass might be gathering dust a bit longer yet,northerly conditions are forecast for the weekend

.

Andy · Unread post by **Andy** » Wed 11/06/2003 18:50

Mt Hutt was due to open on June 7th,they only have a 5cm base which fell on Monday night plus the snowmaking last night.My season pass might be gathering dust a bit longer yet,northerly conditions are forecast for the weekend

Never fear Deano winter will arrive next week week, and hopefully the snow as well

NZstorm · Unread post by **NZstorm** » Wed 11/06/2003 20:00

For cold snaps, no model is particularly reliable. But i have alot of respect for the European prog and it does suggest a colder unsettled change for NZ next week.

http://www.ecmwf.int/products/forecasts ... ots!latest!/

tich · Unread post by **tich** » Thu 12/06/2003 21:12

MetService long-range forecast out to Monday mentions colder and showery weather for much of the South Island (except for the northeast), but no mention of snow yet. Afraid to say this Micheal, but a strong southwesterly pattern looks like becoming established over NZ by early next week. GASP models seem to be predicting 520 thickness level over the east of the South Island on Tuesday I think. Seems like this June won't end up the warmest on record.

Ben
Christchurch (heading for another frost tonight)

Manukau heads obs · Fri 13/06/2003 07:26

yup, the next high looks to be staying over australia, directing a (not as cold) SW airstream over NZ...
a light frost here this morning too ...

NZ Thunderstorm Soc · Fri 13/06/2003 17:15

Yes, ( Aaron) the prognosis looks as though there could be thundery weather for Canterbury, if it was spring or summer????

Johngaul
NZTS

NZstorm · Unread post by **NZstorm** » Fri 13/06/2003 18:17

Yes, air will turn very unstable across NZ next week with thunder/hail in western areas and hopefully the north as well. Snow to low levels in Southland, Fiordland/Westland. Heavy snow falls on the way for Coronet Peak ski area as well as Mt Ruapehu. Likely to be a colder change up the east coast toward the end of week too.

Thunder · Unread post by **Thunder** » Fri 13/06/2003 19:31

Thanks for the good news John! Lets hope things go in our favour.

Cheers
Aaron Wilkinson

tich · Unread post by **tich** » Fri 13/06/2003 20:54

Snow to low levels in Westland/Fiordland? If that happens it'd be for the 3rd year in a row (but this time in June, not May).

Michael · Unread post by **Michael** » Sat 14/06/2003 15:55

Well at least today albeit overcast its not too bad-no wind to speak of and not too cold but we all know about it when the front passes with the windy SW change and the dreadful showers that go along with those

Tomorrow looks more a period of rain followed by occasional showers with westerlies and the SW a day or so when that high gets in the tasman.

NZstorm · Unread post by **NZstorm** » Sun 15/06/2003 08:14

Tasman sea is looking very unstable and showery this morning.
Some large cb's moving into Westland this morning.....perhaps these will be visible from Christchurch. Freezing level over the SI around 1800m but this should lower to 1000m by tonight, i'm picking.

Ski fields should have a good week with plenty of snow fall over the western ranges and MT Ruapehu.

TonyT · Unread post by **TonyT** » Sun 15/06/2003 10:42

Yes, they're visible

Freezing levels usually seem to be lower on the West Coast than in Canterbury in these type of situations. The change on Monday afternoon/evening for Canterbury looks interesting - definitely a chance of thunder in there.

Michael · Unread post by **Michael** » Sun 15/06/2003 10:51

It will probably be the "same ole same old pattern" SW with showers in the North and west of both Islands and far south with a few spreading to Otago and dry elsewhere-probably the best day for TS will be these 2 fronts coming through when the current Northerly pattern turns westerly.
If there is a temp change back to WNW there maybe more.

Chris Raine · Unread post by **Chris Raine** » Sun 15/06/2003 11:45

Cb Tops over western ranges of Southland this morning with Ac and Ci Castellanus too. Quite cool after this morning's rain 4mm

Gene Anton · Unread post by **Gene Anton** » Sun 15/06/2003 13:09

ScottieDavies
Did you see this (today's posting on Snowalert)?
Snow Alert: Whakapapa (1962 m altitude)
3 Day Forecast Issued: 05 am Sun 15 Jun local time
"A heavy fall of snow, heaviest during Sun night
ciao
Gene

Manukau heads obs · Sun 15/06/2003 13:32

Why dont you use your real name Ken?
No one will mind.

ScottyD · Unread post by **ScottyD** » Sun 15/06/2003 17:17

Yip, looks like freezing level will be low enough. Going down south for holiday, so it doesn't have to snow on Ruapehu yet, but for when i get back. Lovely to see some snow on those South Island fields though. Just in time for my Holiday.

Just off Topic, I'm trying to learn more about the weather, but what is the thickness that gets talked about, what is the significance of this?

Scott

g. anton · Unread post by **g. anton** » Sun 15/06/2003 20:36

Snow has fallen in Tasmania, Mt Buller(in Victoria, Aus), also cold
snap in Perth and Melbourne. So what with snow expected in the alps and
central north island over next couple days looks like general cold snap down this whole part of the world. A good omen
ciao
Gene

TonyT · Unread post by **TonyT** » Sun 15/06/2003 21:44

Thickness is a surrogate for temperature.

More specifically, if a weather balloon goes up above a place it records the height and pressure as it goes. If the surface pressure is say 1020Hpa, then at about 200m the pressure will be about 1000Hpa, and at about 5500m the pressure will be 500Hpa (this is about half way up through the atmosphere, at least by weight). The difference between these two heights is called the thickness, because it is a measure of, well, the thickness of the atmosphere (in this case, 5500m-200m=5300m). Actually this is the 1000-500 thickness, you can do a similar calculation for any pair of heights, eg 1000Hpa and 850Hpa.

Now because of the first law of thermodynamics, warm air is less dense than cold air, so it takes up more room. In other words a thicker layer of it is needed to give the same weight or pressure. And conversely, cold air is less dense and is "thinner" for the same weight. So, the thickness between two pressures is a measure of the mean temperature of the layer of air between them.

If we plot thickness values on a map, we can see where areas of cold and warm air are. Note however that it is a mean layer value. For example, a thickness of 5300m (or 530 deca metres, as it is usually referred to) is quite cold and could under some circumstances bring low level snow to Southland or Otago. However, the exact level the snow will fall to is more dependant on the temperature of the lowest layers, not the mean layer temperature. So, some airmasses with a thickness of 530dm will bring snow to Southland and some will not. Thickness is a useful measure, but not a complete one.

No doubt your next question is what range of thickness values to look for. We generally find snow to near sea level is not possible unless thickness values are below about 528dm, and are quite likely when thickness is below 524dm. Typical winter thicknesses over NZ will be in the 540s, while in summer 550s to 560s are more common. Thicknesses over about 570dm are quite warm, even in summer. Snow is unlikely on the main ranges unless the thickness values fall to around 535dm or less.

Michael · Unread post by **Michael** » Sun 15/06/2003 23:01

The map shows an upper air trough over NZ (looks like not lots of isobars in the upper level)and I say it will be westerly in the morning then a strong SW change till Wednesday with snow mostly confined to the west&south then back to WNW by Wednesday evening.

ScottyD · Unread post by **ScottyD** » Mon 16/06/2003 08:45

Tony,

Thanks for explaining that. I'm understanding that much easier now. I'll be on the lookout for some of those lower numbers.

Scott

jeffsweather · Unread post by **jeffsweather** » Mon 16/06/2003 20:07

I see metservice are predicting an overnight low of -5 for Christchurch tomorrow (Tuesday) night. Be a good frost if it gets that cold.
So far this year my coldest temp has been -1 on the 5th May.

tich · Unread post by **tich** » Mon 16/06/2003 21:56

Clear skies and little wind now - the right ingredients for a big frost. But will it stay that way? - MetService is still predicting isolated showers for Canterbury. My parents were travelling from Christchurch to Akaroa this afternoon and noticed a spectacular dark cloud formation out over the peninsula - by the time they got to Hilltop (450 metres asl) it was sleeting and only 2C. Christchurch just got some cloud and a short period of gusty southwesterlies/southerlies about this time.

I hear the Lewis Pass is now closed and its also snowing further west on the saddle towards Reefton. 6PM temps were only about 4C for both Greymouth and Haast with high humidities, so snow could easily have falllen to quite low levels over there.