Weather Forecast Accuracy

[PaulMy]

The weather forecasters often get critical comment when the actual weather doesn't pan out the way it was forecast. However I am amazed how often their longer term forecast is pretty well on the mark. We've had 21 days of "no rain". For over a week now the forecast has been for rain on the weekend, and looks like they will be right (but still waiting).

I have a little script that shows the WU 5 day forecast for my station location and I enter that in a Facebook template that keeps those daily forecasts and I also add the actual weather information from my weather station on that day, so 5 days of forecasts to actual comparison:

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The 5-day Forecast for London/Middlesex, Ontario, Canada
Made on Sunday for: 	Thursday - Mix of sun and clouds. Highs 20 to 22C and lows 8 to 10C.
Made on Monday for: 	Thursday - More clouds than sun. Highs 19 to 21C and lows 8 to 10C.
Made on Tuesday for: 	Thursday - Considerable cloudiness. Highs 18 to 20C and lows 7 to 9C.
Made on Wednesday for: 	Thursday - More clouds than sun. Highs 17 to 19C and lows 7 to 9C.
Made on Thursday for: 	Thursday - Showers possible in the afternoon. Highs 18 to 20C and lows 6 to 8C.
Actual... 		Thursday - Partly sunny, 4.7 hrs sunshine.  High 21.3°C and Low 10.2°C.  Mostly calm, wind gust 32.1 km/h, and 73.2 km wind run.

The 5-day Forecast for London/Middlesex, Ontario, Canada
Made on Sunday for: 	Friday - Partly cloudy. Highs 23 to 25C and lows 10 to 12C.
Made on Monday for: 	Friday - Times of sun and clouds. Highs 21 to 23C and lows 9 to 11C.
Made on Tuesday for: 	Friday - Times of sun and clouds. Highs 21 to 23C and lows 8 to 10C.
Made on Wednesday for: 	Friday - Partly cloudy. Highs 21 to 23C and lows 9 to 11C.
Made on Thursday for: 	Friday - Times of sun and clouds. Highs 21 to 23C and lows 8 to 10C.
Made on Friday for: 	Friday - Cloudy. Highs 21 to 23C and lows 8 to 10C.
Actual... 		Friday - Mostly sunny, 11.6 hrs sunshine.  High 23.9°C and Low 9.0°C.  Wind gust 32.1 km/h, and 95.9 km wind run.

The 5-day Forecast for London/Middlesex, Ontario, Canada
Made on Monday for:	Saturday - Mix of sun and clouds. Highs 24 to 26C and lows 12 to 14C.
Made on Tuesday for:	Saturday - Considerable cloudiness. Highs 23 to 25C and lows 12 to 14C.
Made on Wednesday for:	Saturday - Mix of sun and clouds. Highs 26 to 28C and lows 12 to 14C.
Made on Thursday for:	Saturday - Mix of sun and clouds. Highs 25 to 27C and lows 13 to 15C.
Made on Friday for:	Saturday - Partly cloudy. Highs 25 to 27C and lows 13 to 15C.
Made on Saturday for:	Saturday - Morning clouds followed by afternoon sun. Highs 25 to 27C and lows 13 to 15C.
Actual...		Saturday - Mix of sun and clouds, 6.8 hrs sunshine.  High 28.1°C and Low 7.8°C.  Mostly calm, 27.8 km/h high wind gust, and 69.9 km wind run.

Made on Tuesday for:	Sunday - Chance of showers. Highs 21 to 23C and lows 11 to 13C.
Made on Wednesday for:	Sunday - Showers possible. Highs 24 to 26C and lows 13 to 15C.
Made on Thursday for:	Sunday - Chance of afternoon showers. Highs 24 to 26C and lows 13 to 15C.
Made on Friday for:	Sunday - Showers. Highs 22 to 24C and lows 12 to 14C.
Made on Saturday for:	Sunday - Mainly cloudy and rainy. Highs 20 to 22C and lows 10 to 12C.
Made on Sunday for:	Sunday - Light rain. Highs 22 to 24C and lows 13 to 15C.

Made on Wednesday for:	Monday - Showers possible. Highs 20 to 22C and lows 11 to 13C.
Made on Thursday for:	Monday - Showers. Highs 20 to 22C and lows 10 to 12C.
Made on Friday for:	Monday - Showers possible. Highs 18 to 20C and lows 9 to 11C.
Made on Saturday for:	Monday - Morning light rain. Highs 15 to 17C and lows 9 to 11C.
Made on Sunday for:	Monday - Light rain early. Highs 16 to 18C and lows 7 to 9C.

While I have seen major difference in actual weather conditions compared to the forecast made 3, 4, or 5 days ago, generally it is quite accurate.

Enjoy,
Paul