March to August Temperature Forecast Evaluation

     It is time to look back and see how my Winnipeg forecast, issued daily in the 'Winnipeg Forecast' tab, has faired. I have only evaluated the temperature forecast due to the fact that precipitation and wind forecasts are a little trickier to compare with other forecasts. Different weather agencies have different methods of giving out precipitation and wind forecasts. Some will give you a range, others will give more precise values. This makes it difficult to compare their forecasts with mine. Temperatures are not a problem because all forecasts will give just one specific value as their forecast.

     The evaluation period goes from March 1, 2014 to August 23, 2014. To evaluate how my temperature forecasts have faired, I have compared them to forecasts by various sources: Environment Canada, The Weather Network, Intellicast, Accuweather, A Weather Moment and CBC Manitoba. I will not give the specific results of these sources, because I feel I should not do so if I do not have their permission. Instead, I will compare the results of my forecast with the average result across all sources.

     First, the following table shows what percentage of temperature forecasts were PERFECT. For example, a forecast high of 33°C would be considered a perfect forecast if the actual high was between 32.5°C and 33.9°C.

Table 1: Percentage of temperature forecasts that were perfect (from March 1, 2014 to August 23, 2014)

	My forecasts	Average of all sources	Range of all sources
Day 1 high	51%	41%	31-51%
Day 2 AM low	36%	34%	27-42%
Day 2 high	41%	35%	29-41%
Day 3 AM low	32%	28%	22-36%
Day 3 high	20%	23%	11-35%
Overall	36%	32%	26-36%

     I am happy with the results. My forecasts had the highest percentage of perfect forecasts for both the day 1 and day 2 highs. May and July were the best months for the day 1 forecast with percentages of 58% ad 62% respectively. May was an exceptional month considering the average across all sources was just 32%. Interestingly, day 2 forecasts in July faired better than the day 1 forecasts. 66% of day 2 forecasts were perfect that month. Day 3 high forecasts continue to be my downfall, averaging slightly below average.

    Overall, considering all the temperature forecasts from day 1 to day 3, July was the best month (47%) and March the worst (27%). This is to be expected because temperatures tend to be less predictable in the colder months versus the warmer months.

     The last table below shows the percentage of forecasts that were WITHIN 1°C of the actual value. For example, a forecast high of 33°C would be considered within 1°C of actual if the actual high was between 31.5°C and 34.9°C.

Table 2: Percentage of temperature forecasts that were within 1°C of actual (from March 1, 2014 to August 23, 2014)

	My forecasts	Average of all sources	Range of all sources
Day 1 high	81%	75%	64-81%
Day 2 AM low	66%	63%	56-67%
Day 2 high	67%	66%	57-70%
Day 3 AM low	59%	57%	49-62%
Day 3 high	55%	54%	40-69%
Overall	66%	63%	54-67%

     Again, day 1 high forecasts continue to be my strength. July was the best month with 97% of day 1 forecasts being within 1°C of actual. March was the worst at 68%. Overall, all forecasts from day 1 day 3 were within 1°C of actual 66% of the time, above the average of 63% across all sources. July was my best month at 83% and May the worst at 53%.

     I will continue to compare my forecasts with other forecasts for the foreseeable future. It has become a goal of mine to continue to remain above average and provide the best day 1 to day 3 temperature forecasts for Winnipeg. Unless interest is high, I don't plan to give another evaluation post like this one until next spring. Thanks for reading :)