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How Accurate is the Weather Forecast in Japan?

Japan Meteorological Agency publishes the result of their weather forecasts. It is the percentage of right forecasting cases. 

The below is the average percentage of the right forecasts which predicted a chance of rain (data in 1992 - 2013). If a forecast says that there is a chance of rain, we will have rain with a probability of 83%.

Table : Percentage of right forecasting cases by region (%)

Annual average Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa

Nationwide

Average

Tomorrow's forecast 78 84 85 84 84 78 83
2 days after 74 80 81 80 81 75 79
3 days after 70 75 76 75 75 71 74
4 days after 67 73 73 73 73 69 71
5 days after 66 71 71 70 71 67 69
6 days after 64 70 69 69 69 66 68
7 days after 62 69 68 67 68 65 66
3 - 7 days after, average 66 72 72 71 71 67 70

 

January Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 71 90 85 83 81 78 82
2 days after 68 87 83 80 77 75 80
3 days after 68 84 81 80 75 69 77
4 days after 66 83 79 76 72 68 75
5 days after 64 80 76 73 70 66 73
6 days after 64 80 75 72 68 64 71
7 days after 63 79 74 70 68 62 70
3 - 7 days after, average 65 81 77 74 71 66 73

 

February Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 73 88 86 84 84 80 83
2 days after 70 85 82 81 82 78 80
3 days after 66 81 79 77 77 73 76
4 days after 65 79 77 73 74 70 73
5 days after 64 79 75 71 71 68 72
6 days after 63 77 74 70 69 66 70
7 days after 62 76 72 68 68 64 68
3 - 7 days after, average 64 78 75 72 72 68 72

 

March Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 75 86 86 84 86 81 83
2 days after 71 81 83 81 83 78 79
3 days after 67 77 79 77 79 72 75
4 days after 66 75 76 74 73 70 72
5 days after 64 72 71 69 70 68 69
6 days after 63 71 69 69 69 66 67
7 days after 61 68 67 64 68 64 65
3 - 7 days after average 64 73 73 70 72 68 69

 

April Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 79 85 88 87 88 78 85
2 days after 76 83 84 83 84 74 81
3 days after 71 76 78 76 79 71 75
4 days after 69 74 74 74 75 67 72
5 days after 67 72 73 73 73 67 71
6 days after 65 69 69 70 70 66 68
7 days after 63 67 66 67 67 65 65
3 - 7 days after, average 67 72 72 72 73 67 70

 

May Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 82 85 87 87 88 79 85
2 days after 78 80 83 83 84 75 81
3 days after 72 75 78 77 78 69 76
4 days after 70 72 74 73 75 66 72
5 days after 68 69 72 72 74 65 70
6 days after 66 66 69 70 71 61 68
7 days after 65 65 68 69 70 60 66
3 - 7 days after, average 68 69 72 72 74 64 71

 

June Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 83 79 82 83 83 79 82
2 days after 79 72 77 77 76 75 76
3 days after 73 66 68 68 69 73 69
4 days after 71 62 66 66 66 71 66
5 days after 70 59 61 60 61 71 63
6 days after 68 56 59 59 60 72 61
7 days after 67 56 55 55 58 72 59
3 - 7 days after, average 70 60 62 61 63 72 64

 

July Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 80 77 80 80 81 78 79
2 days after 75 72 76 76 77 74 75
3 days after 68 65 68 69 69 72 68
4 days after 65 63 65 68 68 70 66
5 days after 65 61 64 68 67 69 65
6 days after 63 61 65 68 66 68 64
7 days after 63 61 63 67 66 67 64
3 - 7 days after, average 65 62 65 68 67 69 66

 

August Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 80 78 79 80 79 74 79
2 days after 76 74 76 76 74 70 75
3 days after 69 68 70 71 68 66 69
4 days after 67 67 68 69 66 65 67
5 days after 65 65 67 68 66 65 65
6 days after 63 65 66 67 64 64 64
7 days after 62 64 65 66 62 63 63
3 - 7 days after, average 65 66 67 68 65 65 66

 

September Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 81 82 83 82 84 76 81
2 days after 76 78 79 77 80 73 77
3 days after 70 70 71 71 75 68 71
4 days after 66 66 68 68 73 65 67
5 days after 63 65 65 67 71 64 66
6 days after 62 63 64 66 71 64 64
7 days after 60 61 62 65 71 64 63
3 - 7 days after, average 64 65 66 67 72 65 66

 

October Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 80 85 87 87 87 77 84
2 days after 77 80 83 83 84 74 81
3 days after 71 77 78 78 82 70 76
4 days after 69 75 76 77 81 69 74
5 days after 65 73 75 74 78 68 72
6 days after 63 72 74 73 78 68 71
7 days after 60 71 72 71 76 67 69
3 - 7 days after, average 66 73 75 75 79 68 72

 

November Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 78 88 88 86 86 80 84
2 days after 74 84 85 83 85 75 81
3 days after 71 81 81 79 78 71 77
4 days after 70 78 79 76 75 68 74
5 days after 67 77 76 74 72 67 72
6 days after 65 75 75 73 72 66 71
7 days after 62 74 74 71 70 64 69
3 - 7 days after, average 67 77 77 75 73 67 73

  

December Sapporo Tokyo Nagoya Osaka Fukuoka Okinawa Average
Tomorrow 75 89 86 84 84 81 83
2 days after 71 87 83 80 80 78 80
3 days after 70 84 81 78 77 73 77
4 days after 67 84 79 76 75 72 76
5 days after 65 82 77 73 74 69 73
6 days after 64 82 75 72 73 68 73
7 days after 62 82 76 72 74 66 72
3 - 7 days after, average 65 83 78 74 74 69 74

Source is Japan Meteorological Agency. 降水の有無の適中率の例年値

www.data.jma.go.jp/fcd/yoho/kensho/reinen.html

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