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Education: The most accurate ways to read a rain forecast & get fewer false alarms

It’s always interesting when we get a complaint about a rain forecast, just how often that person hasn’t looked at the ‘big picture’ or read the ‘fine print’.

While forecasts are increasingly becoming localised, the terrain across our regions is so varied that the rain totals do often differ quite a bit from farm to farm, orchard to orchard.

What many people may not realise is that they’re not reading the fine print in the rain forecasts – and when you do that, the forecast comes to life in a far more accurate way.

If you follow all these steps, you’ll have FAR FEWER FALSE ALARMS!

  • Step 1: Look at the Weather icons. You can see when the RAIN SYMBOL shows up.
  • Step 2: Check the Text Forecast. Here you can see what sort of ‘precipitation’ (wet stuff that falls from the sky) is coming: Ie, Rain, showers or snow.

This is where most people stop. They’ve seen the rain icon, they’ve seen “Rain developing” in the forecast. Surely that’s enough?

Not even close.

  • Step 3: What is the % of rain? If it’s below 60% that doesn’t bode well for being a wet day (unless it’s a random thunderstorm).
  • Step 4: What is the rainfall total for that day. If less than 20mm, that’s usually a “low” amount of rain. 20 to 40mm would be more moderate to high and 40mm is high rainfall.
  • Step 5: Now you know how much rain is coming – how is it spread? In one hour? Or many hours across the day? Daytime or nighttime? At RuralWeather.co.nz you can visually see the rain in graph form, hour by hour, for 10 days out. It’s a great way to get a ‘snap shot’ of when the rain starts, peaks and ends.
  • Step 6: It’s all very well knowing what is forecast in your area – but what about the area next to you? It’s important to see the RAIN MAPS to get your head around where the peak rain will be across NZ and to see if you’re in the ‘thick of it’ or just on the fringes (being on the fringes means a higher chance of missing out on the forecast rain).
  • Step 7: Watch our daily weather videos, to get full context.

All of these resources can be found at www.RuralWeather.co.nz and will better help you plan ahead. Forecasters do get it wrong from time to time, but you can significantly increase the accuracy of your local forecasts if you follow the steps above.

If rain matters than much to you then the couple extra minutes to take the extra few steps above will make a big difference.

Here you can visually see how the rain peaks and which days are dry at a glance.
Now break down that day with rain in it and really drill down deeper. In this example, the chance of rain is only moderate at 50% and the rainfall total is just 5.2mm. In other words – even if the forecast says “Rain” it’s not likely to be an overly wet day. You could possibly even still dry the laundry in this set up!
The big picture – Compare your rainfall with regions nearby and work out if you’re in the thick of it all or just on the fringes.
Seeing this will make your local rain forecast make much more sense.

Comments

Obai Tashkandi on 11/02/2021 6:28am

Hi WW, what an awesome article! I love it and I learnt from it! Thank you so much! Although I have a question, when can the rainy days be locked in? Of course, 10 days are way too far, but when are you sure that it will rain, how far?

WW Forecast Team on 11/02/2021 6:18pm

Hey Obai, thanks for the thanks! Highest confidence is within 48 hours, but sometimes even a long range rain event can be pretty much locked in (more so in winter when things move with a bit more speed). If the chance of rain is over 60% more than 5 days out that’s a fairly high chance of rain (but rarely locked in that far out).
– WW

Derek Butcher on 11/02/2021 12:00am

An excellent article and I learned a lot from it. My general weather knowledge has increased a lot since I started visiting this site a few years ago.

Thanks to WW.
Derek

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