Rural Monthly Outlook

Issued 1 December 2017

November 2017

November proved to be a month of extremes. As expected,temperatures swung from unusual heat at the start of the month, to extreme cold during the second week,and then back to extreme warmth for the remainder of the month.Western areas of both Islands saw unsettled westerlies and healthy rainfall for the first 10 days or so of the month. After that, High pressure anchored itself over the country,resulting in an extended dry run for all regions. Notably, the West Coast of the South Island has just experienced a notable run of 18 consecutive dry days.Rainfall that did occur during the last three weeks was highly localised,resulting from afternoon heat showers or thunderstorms.

It was the driest November on record for Christchurch. Christchurch Gardens recorded only 1.3 mm of rainfall, and the Airport 1.4 mm, during the month. This ranks as the 5th driest month, of any month, at the Gardens, in observations that started in 1864. It was also the driest November on record at Oamaru and Ashburton (only 6mm of rain recorded).

Other very dry places include Wellington (Kelburn recorded 17mm, 2nd driest November) and Masterton (8mm, 2nd driest November), as well as Timaru (8mm, 3rd driest November) and Napier (12mm, 3rd driest November).

The Ocean

Sea temperatures right around the New Zealand coastline are currently well above average, having been boosted by light winds and clear skies under the recent High.

A late-developing but relatively weak La Nina event was declared during November. Sea surface temperatures are now below average along the equatorial Pacific, and most models forecast further cooling in the next two months. The most likely outcome is a short-lived La Nina event which maintains through the first quarter of 2018.

The December Outlook

Temperatures in December are expected to run well above average, right across the country.

December is likely to start drier than usual for most regions, but around mid-month, we should see a change to more reliable rainfall in the north and east of the North Island, as well as in Nelson. Highs are expected to continue to favour southern and central New Zealand.

Below average December rainfall is forecast across most of the South Island, as well as for regions in the west and south of the North Island. Near normal rainfall is signalled in the north and east of the North Island, and also Nelson,due to frequent northeasterly wind flows.

Bottom line

Unusually warm. Drier than normal for most regions, except for the north and east North Island and Nelson, where closer to normal December rainfall is forecast.