Wednesday, April 24, 2024

Why Captain Comedown makes for better accuracy

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We aim to forecast the weather most likely to happen, not to forecast the weather most people want says Phil Duncan.
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By Phil Duncan, WeatherWatch

There has been some rain relief in our driest regions over the past week or so and while many regions remain drier than usual for this time of year, the rain and showers that recently fell will be helpful. Northland, Auckland, Waikato, East Cape, coastal Bay of Plenty, dry parts of the lower North Island and parts of Marlborough and Canterbury all had relief. The nature of the fractured fronts means it was hit and miss even within regions. 

As we said recently in our March ClimateWatch update, this month is likely to be dominated by high pressure. Having two highly commercial government forecasters these days competing against each other drives weather narratives that don’t always come true. This can be frustrating for those who need rain and see news stories about possible tropical cyclones that may come down our way and bring relief. has always had one strict philosophy – to forecast the weather most likely to happen, not to forecast the weather most people want. It can be hard to tell everyone you’re not going to get what you want. 

Those who love thunderstorms know all too well we’re quite often “Captain Comedown”, telling people “sorry, we don’t expected any thunder activity today”. Same goes in winter when many people (perhaps not so many farmers!) love the low-level snow. 

Other forecasters and news outlets might hype the excitement value, but with our roots firmly in the same reality you in the rural sector are in, it would be unprofessional of us to hype 1cm of snow that may or may not fall.

We encourage people who see big dramatic weather headlines from other outlets to double-check that forecast with Get that second opinion. 

There is a tropical system north of NZ this week that wants to pull down towards us – but it can only do so if high pressure in NZ clears out of the way. This is the case for ALL tropical lows and cyclones. 

The high-pressure belt that moves from west to east across us is like the main highway, and the tropics is like a small road wanting to pull out and across this busy main highway. In this analogy it means big northern rainmakers can be frustratingly close but may not bring relief. 

For heavy rain in the tropics to reach New Zealand, we first need high pressure around NZ to move out of the way.

Other forecasters and news outlets may not be so interested in that small difference and talk of a major rain event on the way, but we don’t want to give you false hope. Sometimes being honest can be a bit depressing – but in the long run, to be a reliable weather forecaster it pays to park any excitement for what you personally may want and instead always focus on what is most likely to happen.

Highlights this week:

• More high pressure

• Weak cold front(s) will move up the country but won’t deliver much

• A tropical low wants to reach NZ, but high pressure over NZ is the controlling factor. It’s complicated – worth monitoring late week/weekend.

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