Persistent polar activity keeps the cold weather coming

Upper atmosphere temperatures remain influenced by colder polar air masses, shown in blue.  Image based on GFS data.

Upper atmosphere temperatures remain influenced by colder polar air masses, shown in blue.  Image based on GFS data.

If you live on the west coast of New Zealand and feel that the 2016-17 summer has been worse than average you'd be right.

"Since winter 2016, New Zealand has been subjected to persistent polar activity," states Tim Gunn, MetOcean Solutions' weather ambassador. "This results in south-westerly fronts hitting our coastlines, one after the other, bringing with them rain and colder than average temperatures.”

The westerly winds result in upwelling along north-facing coastlines.

The westerly winds result in upwelling along north-facing coastlines.

Polar troughing, which results in westerly wind patterns, is typically replaced by mid latitude synoptic weather systems by mid to late November. These normally bring with them warmer, sunnier and more stable weather. However, this year the change hasn't occurred yet.  

The ocean has been affected too. 

Colder than average temperatures are not stopping enthusiastic bathers in Taranaki.

Colder than average temperatures are not stopping enthusiastic bathers in Taranaki.

"The sea is colder than normal for this time of year in some locations," says Dr Rafael Soutelino, MetOcean Solutions' forecast manager. "On the west coast, the strong pattern of westerly winds which is unusual for this time of year has enhanced upwelling of cooler waters along predominantly north-facing coastlines such as North Taranaki and Bay of Plenty. As a result, those places are experiencing colder than average sea surface temperatures," he explains.