MetService News Release
08 Jan 2018

Rural Monthly Outlook

December 2017
High pressure dominated the weather map during December, and was particularly intense during the first half of the month. Annual dry spell records were smashed at Christchurch and Whanganui, and Westport and Hokitika experienced their longest summer dry spell. However, during the second half of the month, fronts started to move up the country, bringing some welcome showers or rain.

Most of these fronts weakened as they moved north, so many North Island centres still recorded below average December rainfall. After a record dry November, Christchurch and Timaru recorded 37.8mm and 61mm of rain respectively, near average rainfall for December.

It was the warmest December at Auckland Airport since records began in 1962, also Dunedin (since 1962), Queenstown (1968) and Oamaru (1967), while it was the second warmest December on record at Invercargill ( since 1948), Christchurch (1953), Hamilton (1970) and Wellington (1927).

The combination of dryness and warmth meant that soil moisture had hit severe deficit levels (more than 130mm of deficit) by mid-month in many regions of the country. And on the 23rd December drought was declared a medium scale adverse event in Taranaki, Manawatu- Whanganui and Wellington.

The Ocean
Sea temperatures around New Zealand are currently above average, especially about the South Island and west coast of the North Island.

A relatively weak La Nina event persists in the tropical Pacific. Sea surface temperatures are now below average along the equatorial Pacific. Most models predict a weak La Nina event to persist for the remainder of Summer, before transitioning to ENSO neutral during Autumn.

The January Outlook
The first week was dominated by a rapidly developing low pressure system, which brought heavy rain to many North Island locations, as well as the north and east of the South Island. However, high pressure is expected to dominate over the North Island this week, while westerlies will start firing up over the South Island, resulting in a forecast for above average rainfall for the west of the South Island. Near normal rainfall is forecast for the remainder of the South Island. For the remainder of January, the west of the North Island is forecast to receive about average rainfall, while the east of the North Island is expected to run slightly drier than usual.

Temperatures are forecast to track slightly warmer than average in the South Island this week, before tending more towards average for the remainder of the month. In the North Island, temperatures are forecast to be average to slightly above average.

Bottom line:
Above average rainfall in the west and north of both Islands, with about average rainfall elsewhere. Temperatures at or slightly above average.

Official Severe Weather Watches and Warnings are reviewed and re-issued by MetService at least every twelve hours, and more often if necessary. To get the most up to date information on severe weather around the country, or any other forecasts, see metservice.com or on mobile devices at m.metservice.com. You can also follow our updates on MetService TV, at MetService New Zealand on Facebook, @metservice and @MetServiceWARN on Twitter and at blog.metservice.com

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