Severe winter ahead
FRIDAY APRIL 19, 2013
This coming winter may pose problems for skifield operators because access roads to snowfields could be blocked for extended periods, making it a busy season for road gangs. Most cold snaps in winter occur around southern declinations (moon furthest south for the month). Perigee (moon closest to earth for month) exaggerates the effects of the southern declination if they occur together, which this winter they will. The closer the moon is to the earth, the more extreme is the weather, and this year’s closest perigee occurs in late June, which will set us up for a very cold July. Consequently mid-winter to spring should prove to be the coldest part of this year, due to closer lunar perigees from end of May to the third week in August. Very cold temperatures may break records at or near both mid July and mid August. September and October extreme cold spells will bring lamb losses.
After a May of mild temperatures, the cold winter downturn will be rather sudden. The first decent snows of the season come in the last week of May, just after the 26 May southern declination. This turns Central Plateau white, and SI snowfields may get a pre-season dusting. A large depression crosses the entire country around 10-12 June bringing freezing temperatures resulting in snow to low and high levels around 13 -14 June and an icy blast to central NI and Canterbury. The Desert Road and Cheviot to Kaikoura may be threatened with closure. Chains may be needed on most inland state highways, and rural north Canterbury schools may have to close. By 15 June snow could be covering eastern ranges of the NI, also the Southern Alps and central inland areas of the SI. From 20 June, snow comes to within 200 metres in Canterbury and Otago, with more threats of road and school closures. The southern declination 23 June moon is also the closest perigee for the whole year. Snow is expected around 20-24 June for Central Plateau, Methven and Mt Cook Village. The Otira Gorge may be closed and chains may be needed over LewisPass and Tekapo to Fairlie. Further snow dumps arrive around 27-30 June for the Central Plateau, Southland and Otago.
July will be a spectacular month for snow, with reports of road and school closures the subject of daily front page newspaper stories. The sun is furthest from earth in the first week of July, called aphelion, which itself is sufficient to cause a temperature drop. July’s first week brings snow over the south of the NI to about 400 meters, and again to low levels in the east of the SI. In July's second week, the new moon in apogee creates a barometric plunge to the 990s and extreme colder nights bring more snow that threatens power outages and the closure of major roads. Strong coastal winds may bring damage to poorly moored sea-craft, Cook Strait may be rough around 11 July and snow may arrive in Queenstown and Dunedin’s hill suburbs. Early to mid-July may bring snow to 100 metres in the south of the SI. Skiers on Ruapehu around 11 July may find perfect skiing conditions. The third week in July brings cold polar southwesterlies leading up to the next southern declination of 20 July, causing snow and ice to again affect inland country passes and SI roads including Arthurs Pass. Southland roads may also be closed. Following the powerful perigeal full moon of 22 July, snow and ice may force closure of the Desert Road over the whole last ten days of July and may bring snow to sea-level in Southland and Otago
Although more snowfalls are anticipated for early and mid-August, overall August brings below average precipitation for most regions. Significant dry spells, particularly in the SI, see snow events start to lessen. Snowfalls continue in coastal areas through the first week and until around 9 August, but drier periods appear for both islands in the second and fourth weeks. The moon’s next southern declination is on 17 August. The 12-19 August could bring more snow to Central Plateau and to low levels east and south of the SI. Icy conditions may again attempt to close Arthurs Pass. But the next snowfalls are not likely to be until the dying days of August.
The first week of September brings more snow to Mt Ruapehu and SI inland and southern districts, and biting southerlies may bring snow to low levels around Gisborne. In September’s second week, due to southern declination on 13th, a cold southerly blast takes the snow again to Otago and Southland. The most severe time for September may be just after the middle of the month, with the perigeal full moon responsible for snow to low levels in the SI and central NI, affecting inland south Canterbury, Otago and north and west Southland, and again calling out road crews. Unfortunately many lambs may be lost in this period. But from about 19 September, much of the country goes mainly dry for the rest of the month, with the exceptions of a precipitation band that crosses west from Taranaki to Gis/HB as deep as Taranaki to Manawatu, and also the west and south of the SI. There may be perfect skiing conditions on Ruapehu on 21 September. In the fourth week of September, the Manawatu Gorge may receive snow.
The first week of October brings further cold southerlies and heavy snow in the far south, also Otago and south Canterbury, and with the possibility of more lamb losses. Snow may be particularly heavy around Te Anau. Following full moon at the start of the fourth week of October, last gasp snows come to southern and inland areas of the SI, but the warmer temperatures of spring will now release winter’s grip.
For more in-depth reports of daily conditions at NZ's main snowfields please visit our snowfield packages. Each contains 13 documents, comprising
Daily entry spreadsheet showing precipitation, sunshine hours, temperatures max min and dewpoint, wind force, relative humidity, and daily snow expectation for the whole season.
Graphs of all of the above for the whole period.
Tables of days when there will be most precipitation for the season, most sunshine etc
Snow diary covering both islands.
Maps of precpitation distribution for the whole country for months April to December
Chateau for 2013:
Ohakune for 2013:
Mt Hutt for 2013
Craigieburn for 2013
Wanaka for 2013
Queenstown for 2013
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