Rural Monthly Outlook for June 2017:

A drier than normal June likely for the South Island

Issued 31 May 2017

May 2017

During May, intense Highs frequented the New Zealand region, in between some very deep Lows spawned out of the north Tasman Sea. The Highs favoured southern New Zealand, overall, resulting in a drier than usual May over the lower half of the South Island. The Lows produced several heavy rain events for the North Island and upper South Island. The most notable occurred on 11-12 May, (the remnants of Cyclone Donna), and 16-18 May. The first week of May was extremely cold, and temperatures lingered on 'fairly ordinary' after that. A significant cold outbreak on 19/20 May produced the first decent snowfall of the year.

The Ocean

Sea temperatures around the New Zealand coastline remain above average, but generally to a lesser degree than seen over recent months. Waters in Cook Strait and vicinity continue colder than usual. Tropical seas to the north of New Zealand continue warmer than normal, but do not exceed El Nino thresholds.

Looking ahead, there is roughly a 50-50 split between the climate models.Around half reach El Nino levels later in the year, while the other half continue neutral. The tendency of the model runs to back off the likelihood of, and strength of, any future El Nino event speaks volumes. Here in New Zealand, what unfolds with the persistent southern High is far more important to our June weather patterns.

The June Outlook

The persistent High over southern New Zealand looks likely to prevail during the first half of the month, give or take. The weather map will still have fronts and troughs on it during that time, but typically the rain makers won't yield well over the South Island. In contrast, sporadic wet easterlies are likely to continue to affect the North Island for the first third, possibly half,of the month. Once we hit mid-June, all indications are that we see a major shift in weather regime. Highs are predicted to change location, favouring a position over the Tasman Sea for the back half of the month. This is forecast to produce a more traditional, mobile westerly pattern over the country.

A drier than normal June is forecast for the South Island. Near normal rainfall is expected for the north and east North Island, with things running a touch drier for the southwest of the North Island.

For the North Island, the first half of the month is forecast to run colder than usual, while the second half of June should run about average. For Nelson,Marlborough, Canterbury and Otago, expect large temperature swings during June,with the month ending up about average, overall. For the south and west South Island, a warmer than usual June is signalled.

Bottom line

Below normal June totals for the South Island, and a touch drier than usual for the southwest North Island. Close to normal totals for the north and east North Island. A cold first half of June for the North Island. A relatively warm June for the southwest South Island; large temperature swings elsewhere.