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Stormy weather coming

A traditional spring storm is approaching – and it may arrive as soon as Labour Day predicts

Head weather analyst Philip Duncan says it’s a classic set up. “We have a high in the north, a deep low in the south and the two air pressure zones will battle it out over the South Island and lower North Island”.

Mr Duncan says the Southern Alps will play their part too, trapping the heavy rain on the West Coast and helping create gale force nor’westers.

“For those flying on smaller turbo-prop aircrafts over the South Island later on Monday and Tuesday just be aware that delays are possible if those winds crank up”. 

Mr Duncan says passengers should check with their airline or airport’s website on the day of departure.

As predicted last week severe gales (also known as ‘hurricane force’) will be most likely near the Southern Alps and the hills of Otago.  Gale to severe gale force winds are also expected through Cook Strait although swells aren’t predicted to be too big for holidaymakers returning home.

“If the winds make it as far east as Christchurch then it could pose some safety hazards to quake damaged buildings” says Mr Duncan.

Heavy rain is also expected to prompt rain warnings on the West Coast.

The government forecaster, Metservice, says there is a high chance of severe gale and heavy rain warnings being issued across a large portion of the South Island on Monday and Tuesday and a moderate risk of severe gales on Tuesday about Wellington and Wairarapa.



sw on 23/10/2011 1:24am

Means a couple of days of warmer and cloud free weather in Auckland.

weather-nut on 22/10/2011 8:29pm

Disagree about ‘Hurricane Force’ winds’ being the same ‘Severe Gales’. On the commonly used ‘Beaufort Wind Scale’, ‘Severe Gale’ means 10-minute average wind speeds of 41-47 knots (76-87 km/h), whereas ‘Hurricane Force’ means average winds of 64 knots (118 km/h) or more.


WW Forecast Team on 22/10/2011 8:48pm

There’s certainly a grey area here because other forecasters frequently say gusting to severe gale force of 120km/h… but usually we don’t consider a gale to be anything less than 10 minutes.  In America gales and hurricane force winds can be judged in 1 minute parcels rather than 10 minutes.  Because has adopted some American-used terms (because so many NZers are exposed to the American terms, especially with hurricane coverage in the mainstream media) we frequently refer to any wind of 120km/h as hurricane force.   Severe gale can be used for the speeds you’ve indicated above – but also for 120km/h sustained, whereas we prefer to describe that as hurricane force.  

– WeatherWatch Weekends 

weather-nut on 23/10/2011 1:13am

Not sure that I’d entirely agree with the above explanation either.

Yes, the American ‘Saffir–Simpson Scale’ uses a 1 (or 2) minute averaging time as the standard to indicate the peak sustained winds of hurricanes in their jurisdiction of Atlantic and NE Pacific. However, in most of the rest of the world, weather agencies use the definition for ‘sustained winds’ recommended by the World Meteorological Organisation (WMO), which specifies measuring winds (at a height of 10 metres) for 10 minutes, and then taking the average. A simple ratio to convert 10-minute sustained winds to 1-minute sustained winds, is to add about 12-15% to the latter (not a significant difference, but enough to be problematic when comparing hurricanes with tropical cyclones in other parts of the world).

There has also been some debate among enthusiasts as to whether the use of more subjective terms, such as ‘severe-gale, gusting to hurricane-force’, could be somewhat confusing or misleading. Depending on topography etc, gusts are generally anything between 20% to 50% higher than sustained winds. So, a ‘severe-gale with gusts to hurricane-force’ would imply, a ‘severe-gale accompanied by 3-second gusts equivalent to that of average hurricane-force winds’, not a ‘severe-gale with sustained winds to hurricane-force’.

WW Forecast Team on 23/10/2011 1:37am

You make some good points – it’s a shame the entire world doesn’t use one system (certainly very confusing with tropical storms in various parts of the planet).  The fact that the US continue to use a seperate system does seem to cause some confusion – and it’s the US system that tends to make a lot of headlines here, which is why we adopt their terms more so than the British.  Some food for thought for us though – and eventually we’ll have a key on our website to explain all the various terms we use.  We aren’t part of the WMO and have no plans to ever try to be as we like to be independent – but we certainly try to adhere to most, but not all, of their descriptions.

– WW

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