Next Four Days: High Winds, Heavy Rain and Temperatures in the 20’s.

An active Southern Ocean Is set to bring a series of fronts from the southwest over the South Island throughout the week. Strong winds, potentially severe, will deliver rain heavy rain with significant accumulations over the Southern Alps and Westland Ranges. Simultaneously the nor’ wester returns for Canterbury and Otago rising the temperatures 5-7 degrees above the September average especial for the plains and coastal areas of both region.

Model guidance has indicated that some areas could see temperatures into the early 20’s with the hottest day likely to be Wednesday. Below are the temperature anomaly for Monday until Thursday. Anomaly in climatology describes the ‘normal’ or ‘average’ in this case temperatures. Positive number above 0 indicate above normal temperatures while negative numbers represent below the average temperatures expected for September.

Heavy rain is also on the cards, with the heaviest falls falling in Fiordland, South and Central Westland, Canterbury and Otago about the main divide on Wednesday. Accumulations are expected to be around 100-200mm mark in a 24 hour period. Rivers and streams on both sides of the main divide could rise rapidly. Lesser amounts are expected for Northern Westland and Buller.

Severe gales are forecasted over Canterbury High Country especially on Wednesday. While strong gusts could blow onto the plains and across Otago, we aren’t expecting them to become severe.

The extreme weather index (EW Index) maps below indicate the severity of the predicted speeds of the wind gusts in relation to what is normal or expected for the location at this time of the year. The stronger or darker the colours the more severe the index is predicting.

As we head into the week our Significant Weather Outlook will have all the latest up to date details.