Saturday, December 2, 2023

Forecasters up in air on the southern dry

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Two leading weather forecasting agencies agree the eastern North Island can expect to be warmer and drier this year but the jury remains out on just how much drier the eastern South Island will be in coming months.
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Niwa released its seasonal climate outlook in late October while Weather Watch has also entered the longer-term prediction business with its first seasonal forecast extending over the summer.

Weather Watch founder Philip Duncan cautions the business of longer-term weather prediction is not a perfect science and the company hopes to build on its prediction capability and accuracy over time.

However, he predicts drier-than-average conditions extending the length of the North Island’s east coast as far inland as eastern Waikato and accompanied by warmer-than-usual temperatures. 

It is a pattern already firmly established in recent days with areas including southern Hawke’s Bay, Wairarapa and central Northland already experiencing low rainfall and well below average soil moisture. 

Taranaki and southern Wairarapa are expected to be the only areas cooler and wetter than average in the North Island this summer.

With Australia’s drought in play the upper North Island is becoming locked into the high-pressure systems from there affecting rainfall here and increasing warmer airflows over the country’s top half.

Duncan acknowledges there is something of a question mark over the eastern South Island with average to slightly above-average rainfall forecast but highly dependent on the angle of wind over coming months.

“A slight shift to a little more westerly means Canterbury may also be looking at a warmer and drier-than-normal summer.”

The West Coast is likely to be wetter than normal with Southland and Otago leaning towards an average rainfall summer.

Niwa tips a 75% chance of average to below-average rainfall for the eastern North Island. 

But the state-owned climate researcher puts rainfall odds for both the eastern and western South Island at 75% likely to be in the near to above-normal range. 

It also predicts heavy rain in the South Island and western North Island in the first half of summer with an above average risk of flooding.

In picking winners and losers from this summer’s predictions Duncan said it is concerning news for dairy farmers in the upper half of the North Island and windy weather might linger into January for some regions, particularly in the lower South Island.

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