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It’s funny, I often get called a politician by Announcers when they hear my answer to “so what’s the forecast Phil?”. 
“Well Andrew Dickens, from Auckland’s Classic Hits, most likely it will be dry today, but there is a chance there could be some afternoon showers”
“So it’s fine but going to be wet?  You should work at the Beehive”
“yes, maybe”
“Well I’m 50% sure it will rain”
“50%?!  So I could toss a coin?”
“Yes…I guess…but that’s not scientific”
“But 50/50 is?”
Ok, so a hypothetical conversation based on past interviews with Mr Dickens!  But it brings me to an interesting topic.  “Percentage of Precipitation” or “POP”.  This is used widely around the world, including by one of weather partners  Eg: Here you’ll see down the middle a “Precip Chance” column.  There are many scientific ways to read this, but I have a good rule of thumb.  Think of it like this:  If there is a 70% chance of rain across the city of Wellington, then there’s a good chance it will rain.  Being 70% indicates it perhaps won’t be all day…whereas 90% would probably be intense rain.  Drop that POP down to 60%…and it indicates either patchy rain (affecting most of the city, or maybe a heavier period for 60% of the day)…50% and things are getting a little less predictable.  But 50% doesn’t mean it may or may not rain.  In fact it means that there’s a “moderate” chance of rain.  So it’s likely but probably will only be a brief period of rain…or some patchy off and on stuff.  Drop that to 30% and that indicates a few showers might pop up, covering 30% of the city.  10% means just one shower might happen in the afternoon…or some morning or evening drizzle.
POP is something not currently used in New Zealand but TRN’s Weather Watch Centre is introducing it from time to time especially in our forecasts on radio stations Easy Mix and Flava, especially when we’re not confident of rainfall.  To me it’s a more accurate way of portraying the likelihood of rain, rather than saying “Fine with showers” which doesn’t make sense…we prefer “Fine, with a 30% chance of an afternoon shower”…that gives you good confidence to get out there and mow the lawns, but means you’ll keep a wary eye on the sky!
Just another reason to keep in tune with the Radio Network’s Weather Watch Centre, as we introduce great new weather features never before used in New Zealand.



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