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Is this the start of Autumn?

A change to hot and cold weather is affecting the South Island’s east coast – often a tell tale sign that we’re changing seasons.

Temperatures lately in southern and eastern parts of the South Island have been fluctuating wildly with highs up over 30 degrees one day and the mid teens the next.

Alexandra took the national high with 30 degrees on Sunday, but on Tuesday only made it to 16.

Ashburton was on 32 degrees on Monday but yesterday only reached 15.

Invercargill is also showing the tell tale signs that a change of season is beginning.  The city reached 25 on Sunday but yesterday only made it to 16 degrees.  Surrounding days were a pleasant 20 degrees.

Gore had the lowest high yesterday with 14 degrees. 

The temperature changes are usually associated with lows in the Southern Ocean firing up cold fronts.  The cold fronts are preceded by warm winds from the northerly quarter, sometimes bumping temperatures into the late 20s and 30s but are often quickly followed by a cold southerly change – a classic hallmark of Autumn and Spring.

This week we’ve seen that happen and the long range models for the next 10 days show it happening again at least two more times. 

As Autumn approaches the Southern Ocean is likely to fire up stronger westerlies over the South Island and we can expect to see more temperature fluctuations, particularly in the South Island, over the coming weeks.

However with La Nina still strong more tropical lows are expected over the coming two to three months, meaning more warm, wet and humid weather is on the way for the North Island.



Guest Peter on 24/02/2011 10:39am

I notice that the tropics over Australia and to the immediate east are becoming more monsoonally active. What’s the likelyhood of another Cyclone forming?

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