Weather Forecast Links and General Information

Weather and Avalanche Sites for New Zealand

Latest Avalanche Information courtesy of the New Zealand Mountain Safety Council, can be found here: www.avalanche.net.nz

The best weather sites for New Zealand are:

Department of Conservation (Metservice forcasts broken into mountain and national park regions useful for outdoor types):
http://www.doc.govt.nz/templates/page.aspx?id=44798

Metservice (the full metservice site with weather maps, slightly more geared towards thoses in cities and therfore harder to use):
http://www.metservice.co.nz/default/index.php

MetVUW Site:
http://www.metvuw.com/

Mean Monthly Temperatures Around NZ
http://www.niwa.co.nz/edu/resources/climate/meanairtemp

Search and Rescue

National Body: New Zealand Land Search and Rescue Inc (LandSAR)

Search and Rescue Co-ordinators: New Zealand Police

Queenstown area: Wakatipu Search and Rescue

Climbing Seasons

Because New Zealand is surrounded by sea its weather is temperate, some sort of climbing activity can be done all year round. Some climbers claim that winter produces as many fine climbing days in the alpine regions as summer. but no documentary evidence can be found to support this claim.

Activities like rockclimbing and tramping can he done throughout the whole year, but the summer period proves to be the most popular. The North Island receives most of its rainfall during the winter months which can interrupt some of these activities. In winter additional clothing will be required.

Most alpine climbing is carried out during January when many Kiwis take their annual vacation. The better weather is usually obtained during the February-March period. March is usually best for the Darrans.

The most preferred winter months are August- September. But climbing is not restricted to these periods only. Stable fine weather can often be obtained outside the above four months. For instance the West Coast often has an extended dry period during June and July.

During the February-March period the weather patterns are more stable, and daylight hours are adequate, plus the heavy winter snows have disappeared. Unfortunately, as the summer progresses access, many alpine climbs become more difficult as crevasses are exposed on the glaciers. The status of crevasses is of significance because the majority of New Zealand mountaineering is carried out on snow and ice rather than rock.

General Weather Information

New Zealand straddles the 40 degree south latitude, which the sailors refer to as the "Roaring Fourties'. This name comes about because of the strong westerly winds which were very helpful for pushing the sailing ships. Therefore New Zealand's weather is dominated by these westerly winds which flow across the Tasman sea collecting moisture. The airflow is forced to rise and cool as it passes over the country's alpine backbone. The winds then release their load of water on the western slopes of the alps in the form of rain or snow. The air, now drier, then descends to the east, warming as it goes and creating a warm, dry wind over the eastern plains.

This weather pattern follows approximately a 6-10 day cycle. The westerly airflow is caused by depressions (bringing cold fronts) that pass to the south of the country. Between these cold fronts, ridges of high pressure (anti-cyclones) bring light winds and generally fine weather. Sometimes a depression will travel directly over New Zealand, bringing large amounts of rain, but if a slow moving anticyclone passes over the country, long periods of fine weather can be experienced.

The only thing certain about New Zealand weather is its uncertainty. Long storms are quite possible, like one experienced by two climbers in November 1982 when they where trapped on the summit ridge of Mt Cook for 14 days, but as a rule a storm will only last for two to three days, and is often followed by a couple of days of fine weather.

The South Island's free air freezing level is usually about 1650 metres in winter and 3200m in summer, but within the Alpine regions it is usually lower.

During the winter period it can get cold in the Alpine regions. Mt Cook village average winter temperature is 2 degrees Celsius while in summer it will average 14 degrees Celsius. As a general rule the temperatures declines by approximately 6.5 degrees Celsius every 1000 metres altitude gained. In Christchurch temperatures climbing into the 30's are not uncommon during the summer months.

In the North Island the weather patterns are not so pronounced, and the temperatures are generally a few degrees warmer than in the South Island.

Common Weather Patterns

Nor'westerly

Northwesterly airflow over the South Island will bring rain to the West Coast, high winds in the mountains with rain sneaking over to the main divide for a few kilometres. The further east of the divide, the drier and less clouded the skies become. While the winds will increase in intensity until the Nor'west gets to the east coast, where it is very warm and dry. From the eastern plains you will see dark grey clouds obliterating the Southern Alps, while ridges of tightly formed arches will be found above the inland eastern plains, clear skys will be found on the eastern coast. Advice: head to the east coast crags, take your sunblock and swimming gear.

Southerly

The country's snow storms come from the southerly quarter. A southerly storm progresses up the east coast, bringing a big drop in termperatures and a cool rain (summer), or a snow storm (winter). If the storm comes from the southeast during winter the low country to the east will get a heavy dumping of snow and many of the country's high roads and passes are closed. During winter it is rare for a southerly to last longer than three days while during the summer a southerly does not last very long, ranging from hours to a couple of days. Southerlies also bring good news for climbers. Advice: If in a hut, find a good book, if not in the mountains, make preparations for a trip and start walking in to a high hut during the tail end of the bad weather.

Southerly Clearing

After the southerly front has passed through, climbers will start to see increasing patches of blue skies on the southern horizon. This is very good news. The clouds will be moved away by the cool southerly airflow and a period of fine weather will follow. The initial period will be cool but unbelievably fine while as the fine spell progresses air temperatures will rise as the air flows moves into the westerly quarter. Advice: Climb. Pick an ice climb, save the rock climbs for the warmer westerly.

Westerly

A light warm westerly airflow does bring some cloud cover on the western side of the divide. This is often referred to as "West Coast Crud' by climbers. Early morning the West Coast is often clear of cloud. As the day develops, white fluffv cloud starts forming over the rainforests at about 1200m. As the morning progresses the "Crud" intensifies, and rises up the valley systems onto the snowfields. At about midday anybody east of the divide will see the "crud" flowing over the divide at its low points. Anything flowing over the divide will quickly disperse within a few kilometres of the divide. The "Crud" will start to disperse during the evening leaving a clear night. Advice: Climb. On the western side of the divide you may be engulfed by cloud, but don't panic, just make sure you can navigate yourself back to the hut in no visibility.

Westerly Deterioration

As the westerly portion of the weather cycle progresses, the "west coast crud' becomes more intense and will not retreat during the evening. High cloud can be seen moving eastward above the "westcoast crud" layer. As the sky greys this high cloud intensifies and the air temperatures will rise. The increase in night temperatures is particularly noticeable. At this time, the wind velocity increases and arched shaped lenticular clouds are seen in the sky, or sitting over major summits. These lenticular clouds, known as 'Hogs Backs', indicate high winds at altitude and are the forewarners of a nor'westerly. Advice: abandon high camps, and head for reliable shelter while you can still move. Last minute ascents can often be sneaked in on the more easterly mountains like the Malte Brun Range at Mt Cook, or Cloudy Peak, or the Arrowsmiths.

Two other weather phases that do not occur very often are worthy of mention.

Easterly

This often brings light warm rain with very little wind to the east coast, and sometimes as far inland as the Alpine regions. Fine weather is experienced on the Westcoast. Most east coast farmers are overjoyed with this rain. Advice: Climb on the West Coast. Avoid the east coast rock.

Northeasterly

Perhaps one of the rarer weather occurances. This brings an extremely heavy downpour of rain (and flooding) to the east coast region, in particular to East Cape (North Island). Advice: go to Fiordland, and the Darrans. It will most likely have stopped raining there.

Blue Skies and Sunburn

Most northern hemisphere climbers will find the skies over New Zealand extremely blue. This is primarily because of the relatively low level of pollutants in the air. This means sunburn can be a major problem. During the summer period weather forecasts often include a "Burn Factor'. This represents the number of minutes before unprotected skin suffers sunburn. Periods may be as short as 12 minutes during the summer months, and shorter times should be expected when at altitude or on a glacier.

Sources of Weather Information

An accuracy rate of over 80% is being claimed for forecasts for the following day, while the forecasters are claiming over 70% accuracy two days in advance. One point to remember when looking at weather maps in New Zealand; Anticyclones (High pressure areas) rotate in an anticlockwise direction, and lows rotate clockwise, the opposite to the northern hemisphere.

Up to date weather forecasts can be obtained at the local Department of Conservation (DoC) field centres, or:

Online
Brief area forecasts, including mountain forecasts (Metservice)
Australia/New Zealand situation maps
Victoria University has satelite and radar images, upper air data and forecast charts
Bill Atkinson Mountain Guides at www.sunrockice.co.nz has a good selection of links, including animated six-day forecasts showing precipitation and pressure
Telephone
(a small charge is incurred)
Mountain Forecast General: 0900 99966
Tongario Region (Central North Island): 0900 99915
Canterbury high Country: 0900 99926
Southern Lakes: 0900 99981
Television
Teletex Page 465
Radio
Radio New Zealand National Programme:
Mountain forecast: after 4.00pm News
Five-day forecast: 12:30pm
TV and Newspapers
The television forecasts are generaly too brief to be of use for climbers, but have the advantage of quickly showing you a "Situation Map'. All local and national daily newspapers carry a detailed forecast with a situation map. These can be very helpful.

Sunrise/Sunset Times

The times listed below are sunrise and sunset at Christchurch. Times given are New Zealand Standard Time (NZST). Add one hour to obtain New Zealand Daylight Time (NZDT).

Month Sunrise Sunset
20 January 0513 2007
19 February 0554 1932
21 March 0632 1841
20 April 0708 1749
20 May 0741 1711
19 June 0802 1659
19 July 0756 1716
18 August 0721 1747
17 September 0629 1820
17 October 0536 1855
16 November 0455 1934
16 December 0443 2007

Auckland has 40 minutes less daylight during summer than Christchurch, while during winter the opposite applies. Sunrise and sunset times can be obtained from the Carter Observatory in Wellington, ph (04) 472 8167.