Meadowbank Aerodrome
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Meadowbank Aerodrome clear sky chart from 2005-11-05 to 2017-09-22.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
44%
14544
5%
46124
4%
14532
46%
14532
12%
36503

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
53%
955
8%
3402
8%
955
56%
955
12%
2547
January16th to endNight
48%
968
10%
3318
10%
968
51%
968
15%
2402
February1st to 15thNight
62%
875
10%
2727
8%
875
64%
875
19%
1946
February16th to endNight
52%
789
9%
2183
6%
789
54%
789
17%
1662
March1st to 15thNight
61%
786
11%
2226
11%
786
63%
786
22%
1576
March16th to endNight
60%
576
13%
2040
12%
576
63%
576
20%
1373
April1st to 15thNight
49%
539
4%
1593
3%
539
50%
539
19%
1170
April16th to endNight
50%
534
0%
1272
0%
534
50%
534
17%
1028
May1st to 15thNight
41%
237
0%
957
0%
237
41%
237
11%
719
May16th to endNight
33%
187
0%
665
0%
187
33%
187
9%
521
June1st to 15thNight
40%
180
0%
414
0%
180
40%
180
19%
334
June16th to endNight
51%
180
0%
180
0%
180
51%
180
45%
180
July1st to 15thNight
60%
170
0%
477
0%
170
60%
170
26%
322
July16th to endNight
47%
188
0%
711
0%
177
48%
177
14%
496
August1st to 15thNight
56%
312
0%
1027
0%
311
56%
311
22%
662
August16th to endNight
44%
573
0%
1428
0%
573
44%
573
18%
1118
September1st to 15thNight
37%
540
3%
1662
1%
540
38%
540
12%
1330
September16th to endNight
23%
538
3%
1889
2%
538
25%
538
5%
1639
October1st to 15thNight
24%
748
3%
2090
2%
748
25%
748
6%
1893
October16th to endNight
17%
880
1%
2537
1%
880
18%
880
2%
2416
November1st to 15thNight
30%
875
3%
2841
2%
875
30%
875
5%
2568
November16th to endNight
41%
930
5%
3237
3%
930
45%
930
8%
2645
December1st to 15thNight
51%
960
5%
3474
6%
960
52%
960
8%
2856
December16th to endNight
44%
1024
4%
3774
5%
1024
44%
1024
8%
3100

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
12%11%5%9%8%46%6%6%7%20%
48865
Night
9%10%5%10%9%5%8%8%8%9%14%
46193
Cloud CoverDay
12%11%5%9%8%46%6%6%7%20%
48873
Night
9%10%5%10%9%5%8%8%9%9%13%
46198
TransparencyDay
60%7%13%15%3
48450
Night
61%7%12%14%3
46124
SeeingDay
17%316%26%24%11%
7780
Night
13%217%30%25%10%
14554

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
6%9%5%10%7%6%9%9%6%14%13%
537
16th to endDay
38%5%7%9%5%9%10%12%14%14%
906
February1st to 15thDay
1426%10%7%11%10%15%17%11%
1137
16th to endDay
26%411%10%5%7%9%12%11%18%
1289
March1st to 15thDay
5%6%49%8%47%9%11%18%14%
1736
16th to endDay
35%38%7%5%11%10%14%13%17%
2184
April1st to 15thDay
6%11%5%7%7%5%9%11%10%7%16%
2355
16th to endDay
8%10%411%13%8%10%7%5%5%13%
2686
May1st to 15thDay
12%13%7%11%13%5%6%44416%
2992
16th to endDay
10%14%10%15%10%45%34415%
3446
June1st to 15thDay
16%16%6%7%5%34446%22%
3545
16th to endDay
13%10%36%6%35%5%6%7%31%
3780
July1st to 15thDay
13%5%35%7%36%6%7%8%31%
3453
16th to endDay
14%7%37%6%36%5%5%7%30%
3403
August1st to 15thDay
15%6%25%6%34447%39%
2926
16th to endDay
22%9%36%7%35%45%5%25%
2772
September1st to 15thDay
20%16%47%6%34346%21%
2298
16th to endDay
22%21%8%9%6%3422315%
1872
October1st to 15thDay
18%18%9%15%9%5%5%3239%
1540
16th to endDay
21%23%7%12%11%46%4223
1334
November1st to 15thDay
11%21%9%14%9%45%7%5%35%
1017
16th to endDay
410%6%10%11%5%10%10%12%6%9%
721
December1st to 15thDay
36%6%12%11%9%11%9%9%11%6%
486
16th to endDay
412%8%10%11%7%9%10%8%8%6%
450
January1st to 15thNight
5%7%5%9%9%6%9%9%12%12%11%
3401
16th to endNight
45%49%8%5%9%11%10%16%12%
3318
February1st to 15thNight
2436%8%7%12%11%14%17%11%
2723
16th to endNight
15%6%11%11%6%9%9%9%15%13%
2183
March1st to 15thNight
5%7%36%7%5%9%9%11%16%16%
2213
16th to endNight
25%48%8%48%12%11%12%20%
2040
April1st to 15thNight
7%8%48%9%5%6%8%8%9%23%
1593
16th to endNight
6%10%49%10%7%10%6%46%22%
1272
May1st to 15thNight
10%13%6%10%7%5%6%35%5%25%
957
16th to endNight
12%12%7%16%8%34435%21%
665
June1st to 15thNight
14%17%9%44325%35%27%
414
16th to endNight
14%10%235%15%7%7%8%33%
180
July1st to 15thNight
11%7%26%5%345%5%6%41%
507
16th to endNight
14%7%37%6%3445%9%31%
763
August1st to 15thNight
13%6%15%4245%6%8%40%
1032
16th to endNight
24%8%26%6%345%47%27%
1428
September1st to 15thNight
20%14%47%6%35%45%5%23%
1662
16th to endNight
22%18%9%10%6%2334313%
1889
October1st to 15thNight
15%19%9%15%8%4443311%
2090
16th to endNight
21%21%7%13%13%5%43322
2537
November1st to 15thNight
11%18%9%13%11%5%7%7%7%35%
2841
16th to endNight
5%10%6%10%13%6%10%10%12%5%7%
3237
December1st to 15thNight
47%5%11%13%8%10%10%11%9%6%
3474
16th to endNight
6%13%7%11%9%5%9%10%10%8%7%
3774

Percentage Cloud Cover NW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
5%8%7%9%8%6%8%9%7%14%12%
537
16th to endDay
38%47%9%5%9%11%12%13%13%
906
February1st to 15thDay
1427%10%7%11%10%16%16%10%
1137
16th to endDay
26%410%10%5%7%9%12%11%18%
1289
March1st to 15thDay
46%48%9%48%9%11%18%13%
1746
16th to endDay
35%37%7%5%11%11%14%12%16%
2182
April1st to 15thDay
6%11%47%8%5%10%11%10%7%16%
2355
16th to endDay
8%10%410%14%9%10%7%5%5%13%
2686
May1st to 15thDay
12%14%7%11%13%6%6%44415%
2992
16th to endDay
10%15%10%17%9%45%345%15%
3446
June1st to 15thDay
16%17%7%7%6%34446%22%
3545
16th to endDay
13%10%46%6%35%5%6%7%30%
3780
July1st to 15thDay
13%5%35%7%37%6%7%8%31%
3453
16th to endDay
15%8%36%6%36%6%5%7%30%
3403
August1st to 15thDay
14%6%36%5%3345%6%39%
2926
16th to endDay
22%9%37%7%34445%25%
2772
September1st to 15thDay
21%16%5%7%6%34445%21%
2298
16th to endDay
22%21%8%10%6%2422314%
1872
October1st to 15thDay
17%18%8%16%10%443239%
1540
16th to endDay
20%23%8%13%11%444323
1334
November1st to 15thDay
11%21%9%15%9%47%6%5%44
1017
16th to endDay
311%6%10%12%6%11%11%11%6%8%
721
December1st to 15thDay
28%5%13%12%10%10%9%11%10%6%
486
16th to endDay
412%7%11%12%7%8%12%8%7%7%
450
January1st to 15thNight
5%7%410%10%6%9%9%12%12%10%
3402
16th to endNight
5%5%410%9%5%9%11%11%15%11%
3318
February1st to 15thNight
2436%9%7%10%12%15%17%10%
2716
16th to endNight
16%5%11%10%6%9%9%10%15%12%
2183
March1st to 15thNight
6%6%46%7%5%9%9%12%16%16%
2226
16th to endNight
25%38%8%48%13%11%12%20%
2038
April1st to 15thNight
7%7%5%8%10%5%7%8%7%9%22%
1593
16th to endNight
6%10%5%9%10%7%10%5%46%22%
1272
May1st to 15thNight
11%14%410%7%47%445%24%
957
16th to endNight
11%11%8%17%8%25%44421%
665
June1st to 15thNight
15%16%9%6%433445%27%
414
16th to endNight
12%10%345%137%7%9%32%
180
July1st to 15thNight
11%6%36%5%25%5%5%6%41%
507
16th to endNight
14%6%38%6%5%25%410%31%
763
August1st to 15thNight
13%6%25%5%35%5%5%8%40%
1032
16th to endNight
24%7%26%6%34447%27%
1428
September1st to 15thNight
19%15%5%6%6%35%45%5%22%
1662
16th to endNight
22%17%9%11%6%2434313%
1889
October1st to 15thNight
15%19%10%14%8%4443311%
2090
16th to endNight
20%22%7%13%13%45%2322
2537
November1st to 15thNight
11%18%9%13%11%6%6%7%6%35%
2841
16th to endNight
5%11%6%10%12%7%10%10%12%5%7%
3237
December1st to 15thNight
47%5%11%13%8%11%10%11%8%7%
3474
16th to endNight
5%14%6%11%9%5%9%10%11%8%7%
3774

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
57%8%16%13%3
537
16th to endDay
52%8%11%17%10%
906
February1st to 15thDay
48%8%20%18%3
1137
16th to endDay
49%8%12%19%8%
1289
March1st to 15thDay
48%7%16%19%7%
1746
16th to endDay
47%7%14%18%10%
2184
April1st to 15thDay
57%6%11%15%8%
2355
16th to endDay
70%5%8%12%2
2686
May1st to 15thDay
71%5%8%9%4
2992
16th to endDay
72%5%8%12%
3451
June1st to 15thDay
63%5%12%14%2
3545
16th to endDay
51%8%17%19%2
3780
July1st to 15thDay
47%8%15%24%3
3254
16th to endDay
51%10%16%17%3
3192
August1st to 15thDay
44%8%18%22%5%
2906
16th to endDay
60%7%15%14%1
2772
September1st to 15thDay
65%7%12%14%1
2298
16th to endDay
76%5%8%8%
1872
October1st to 15thDay
81%5%9%3
1540
16th to endDay
86%5%42
1334
November1st to 15thDay
79%6%5%6%1
1017
16th to endDay
65%7%13%9%2
721
December1st to 15thDay
63%11%12%12%
486
16th to endDay
66%7%12%11%2
450
January1st to 15thNight
56%9%16%15%2
3402
16th to endNight
52%7%12%18%8%
3318
February1st to 15thNight
46%10%17%21%3
2727
16th to endNight
54%7%10%20%6%
2183
March1st to 15thNight
46%8%16%21%6%
2226
16th to endNight
45%8%12%22%10%
2040
April1st to 15thNight
52%6%9%18%11%
1593
16th to endNight
60%5%8%18%5%
1272
May1st to 15thNight
60%6%11%13%8%
957
16th to endNight
66%47%19%1
665
June1st to 15thNight
58%6%12%19%2
414
16th to endNight
43%9%22%20%3
180
July1st to 15thNight
41%7%12%33%4
477
16th to endNight
50%8%17%21%2
711
August1st to 15thNight
40%9%19%26%4
1027
16th to endNight
55%7%18%16%2
1428
September1st to 15thNight
62%7%13%15%1
1662
16th to endNight
75%6%8%8%1
1889
October1st to 15thNight
78%6%8%6%
2090
16th to endNight
87%5%5%2
2537
November1st to 15thNight
79%6%6%7%
2841
16th to endNight
66%8%13%9%2
3237
December1st to 15thNight
65%9%12%11%
3474
16th to endNight
65%9%13%9%1
3774

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
6%16%26%33%16%
30
16th to endDay
18%36%34%25%12%
32
February1st to 15thDay
2432%30%30%
75
16th to endDay
6%14%22%38%18%
81
March1st to 15thDay
2215%16%44%18%
90
16th to endDay
7%113%33%29%14%
168
April1st to 15thDay
11%316%37%23%7%
449
16th to endDay
11%216%27%25%16%
450
May1st to 15thDay
16%216%26%23%13%
468
16th to endDay
15%218%27%24%11%
788
June1st to 15thDay
23%417%25%21%7%
855
16th to endDay
16%417%29%23%9%
855
July1st to 15thDay
14%314%24%28%14%
815
16th to endDay
18%317%29%21%9%
692
August1st to 15thDay
17%115%21%24%18%
493
16th to endDay
25%213%22%24%12%
523
September1st to 15thDay
28%416%20%20%10%
453
16th to endDay
24%121%21%24%6%
135
October1st to 15thDay
22%322%17%30%4
90
16th to endDay
30%219%22%19%6%
93
November1st to 15thDay
30%9%9%24%24%1
53
16th to endDay
23%6%43%16%10%
30
December1st to 15thDay
10%343%23%20%
30
16th to endDay
6%6%31%28%28%
32
January1st to 15thNight
6%215%29%31%14%
960
16th to endNight
6%221%32%24%11%
968
February1st to 15thNight
3315%32%28%16%
880
16th to endNight
3118%35%28%13%
789
March1st to 15thNight
8%113%35%29%12%
786
16th to endNight
3215%37%28%13%
576
April1st to 15thNight
10%319%35%22%7%
539
16th to endNight
10%313%32%31%8%
534
May1st to 15thNight
16%218%31%23%8%
237
16th to endNight
18%314%28%26%9%
187
June1st to 15thNight
21%420%28%21%3
180
16th to endNight
16%218%38%22%1
180
July1st to 15thNight
13%214%30%34%4
170
16th to endNight
14%420%30%28%1
188
August1st to 15thNight
14%116%32%27%6%
312
16th to endNight
28%312%26%25%4
573
September1st to 15thNight
28%315%29%17%5%
540
16th to endNight
32%318%26%15%3
538
October1st to 15thNight
24%221%25%21%4
748
16th to endNight
32%218%25%15%6%
880
November1st to 15thNight
18%317%28%22%9%
875
16th to endNight
9%320%28%25%13%
930
December1st to 15thNight
6%114%30%28%18%
960
16th to endNight
9%316%27%27%15%
1024
Page generated at 2017-09-23 05:43:43. Version ac04

Copyright 2017 A. Danko


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