Southwesters keep rainfall high in January

January 2021 will be remembered by many as the month of umbrellas.

Niwa’s January weather review showed mean sea level pressure was lower than normal over and just east of New Zealand, resulting in more southwesterly winds than normal.

This kept temperatures nearer average and rainfall unusually high for much of the South Island.

Niwa meteorologist Seth Carrier said moderate La Nina conditions continued in the tropical Pacific, but the impacts on weather patterns over New Zealand were not those typically expected.

Oamaru had its wettest January since records began in 1941, recording 133mm for the month (305% of normal).

Clyde recorded its wettest January since 1978, with 147mm for the month (282% of normal) — 35% of its normal annual rainfall total.

Ranfurly and Lauder recorded their second-wettest January and Waimate and Cromwell their third-wettest.

Mr Carrier said the monthly totals were significantly driven by a major rain event early in January, when an area of low pressure passed directly over New Zealand and led to widespread flooding.

"On January 2, between 150 and 200 holiday-makers had to be evacuated when the Otematata River burst its banks.

"Another 200 people attending the Whare Flat Folk Festival near Dunedin were stranded due to rising water levels on the Silverstream.

"In Central Otago, the water supply for Patearoa was shut down due to the flooding, and a water tanker was brought in for affected residents.

"In Middlemarch, residents were advised not to flush their toilets and avoid drinking water from bores as it was likely to be contaminated.

"In Earnscleugh, near Clyde, the Fraser River breached its banks, causing extensive damage and significant crop losses to orchards and vineyards in the area."

He said between 9am January 1 and 9am January 3, Alexandra recorded 120.4mm of rain, which was equivalent to 33% of the town’s normal annual rainfall.

Many roads in the lower South Island were closed due to flooding and slips, including a stretch of State Highway 1 between Maheno and Reidston, and State Highway 6 between Kingston and Queenstown.

State Highway 87, from Kyeburn to Outram, was closed due to the washout of the Kokonga Bridge, and SH83 from Otematata to Aviemore was also closed due to flooding.

However, the month was not all cold and wet weather, he said.

From January 25-28, a very warm air mass originating from Australia, combined with westerly foehn winds, caused the mercury to soar, resulting in near-record temperatures across the southern region.

Dunedin (Musselburgh) recorded 33.4degC on January 26 — its third-hottest January temperature since 1947; and Nugget Point recorded 30.2degC on the same day — also its third-hottest since 1970.

john.lewis@odt.co.nz

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