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Forecaster performance - July 2019 heatwave

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Posted (edited)

Between 17th and 24th July, I logged the max temperatures being forecast for Chelmsford by the main weather websites, for the period of 22nd to 25th July (i.e. the heatwave period). I thought this was worthwhile as there was uncertainty over the peak day of heat and what the temperatures would be.

I developed a crude scoring mechanism which I weighted so the more a forecast was out the closer it got to the date, the higher the score. Therefore, the lower a score, the better. I then took averages which produced the following ranking:

1. WeatherPro/BBC* 7.7
2. WeatherOnline 10.1
3. Google (weather.com) 10.2
4. Accuweather 11.8

5. MetOffice 13.7
6. NetWeather 14.6
7. MetCheck 20.3
* Grouped together as they're both MeteoGroup and their forecasts are almost identical.

This is far from scientific, but I wasn't surprised to see WeatherPro come top, Metcheck come bottom and the MetO not do very well. I always thought WeatherOnline over-did temperatures but they did well here.

The graphs below show how each site did with its forecasts, versus the actual recorded max (at Writtle, MetO's Chelmsford station). Some are missing where the site didn't offer a forecast beyond five days. The 'top 2' and 'bottom 2' are based on the scoring which is calculated as described above. Therefore a forecast which was accurate in the end would score less overall if it was way out a few days before.

Mon 22/7

Top 2: Accuweather and WeatherPro/BBC
Bottom 2: Netweather and Metcheck

Tue 23/7

Top 2: Google and WeatherPro/BBC
Bottom 2: Netweather and Metcheck


Wed 24/7

Top 2: Weather Online and WeatherPro/BBC
Bottom 2: MetOffice and Metcheck


Thu 25/7

Top 2: WeatherPro and Weather Online
Bottom 2: Netweather and Metcheck


Edited by h2005__uk__

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