Gatineau Gliding Club
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gatineau Gliding Club 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
37%
14660
13%
46902
10%
14629
42%
14629
18%
33477

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
22%
720
7%
2506
5%
716
25%
716
8%
2021
January16th to endNight
28%
768
10%
2667
8%
768
33%
768
12%
2008
February1st to 15thNight
26%
703
10%
2287
7%
701
31%
701
12%
1775
February16th to endNight
32%
631
14%
1929
10%
631
39%
631
16%
1446
March1st to 15thNight
29%
720
13%
2127
10%
720
34%
720
16%
1606
March16th to endNight
38%
768
21%
2016
11%
768
45%
768
26%
1403
April1st to 15thNight
32%
718
15%
1796
7%
718
35%
718
22%
1325
April16th to endNight
33%
645
17%
1725
8%
645
39%
645
24%
1217
May1st to 15thNight
37%
360
17%
1440
16%
360
44%
360
17%
948
May16th to endNight
44%
375
13%
1497
13%
374
52%
374
19%
958
June1st to 15thNight
41%
360
9%
1440
10%
360
47%
360
16%
996
June16th to endNight
47%
360
9%
1440
14%
360
50%
360
19%
910
July1st to 15thNight
61%
340
13%
1360
21%
340
64%
340
26%
758
July16th to endNight
62%
376
13%
1418
19%
354
64%
354
24%
821
August1st to 15thNight
59%
410
14%
1481
15%
408
62%
408
23%
928
August16th to endNight
59%
729
19%
1875
12%
729
62%
729
36%
1180
September1st to 15thNight
55%
720
15%
1800
9%
720
56%
720
30%
1247
September16th to endNight
55%
685
22%
1859
15%
685
58%
685
32%
1191
October1st to 15thNight
39%
660
18%
1980
13%
660
46%
660
22%
1368
October16th to endNight
33%
704
11%
2221
8%
704
38%
704
15%
1670
November1st to 15thNight
36%
700
17%
2310
15%
700
42%
700
18%
1634
November16th to endNight
28%
720
11%
2520
9%
720
32%
720
11%
1917
December1st to 15thNight
24%
720
7%
2520
5%
720
28%
720
9%
1988
December16th to endNight
19%
768
9%
2688
5%
768
24%
768
8%
2162

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
18%8%36%5%3445%6%33%
47989
Night
18%9%36%5%34445%33%
47071
Cloud CoverDay
18%8%36%5%3445%6%33%
47998
Night
18%9%36%5%34445%32%
47077
TransparencyDay
50%5%12%19%9%1
47676
Night
52%5%11%19%9%1
46902
SeeingDay
22%5%22%27%16%5%
5528
Night
23%5%24%33%12%
14661

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
23%14%5%9%6%2433421%
1432
16th to endDay
14%14%5%9%6%345%46%24%
1554
February1st to 15thDay
14%12%5%11%7%36%445%24%
1575
16th to endDay
19%10%5%9%7%35%345%26%
1543
March1st to 15thDay
18%10%48%7%36%43427%
1823
16th to endDay
18%6%345%24345%40%
2208
April1st to 15thDay
22%9%35%423435%34%
2152
16th to endDay
20%7%36%5%33336%35%
2243
May1st to 15thDay
20%7%35%6%33446%33%
2511
16th to endDay
19%6%245%3445%7%35%
2618
June1st to 15thDay
22%6%25%5%35%46%6%30%
2520
16th to endDay
18%6%26%335%6%6%8%31%
2520
July1st to 15thDay
13%425%5%35%5%7%8%37%
2520
16th to endDay
11%5%35%5%35%6%7%9%35%
2654
August1st to 15thDay
12%5%26%6%35%5%6%8%37%
2466
16th to endDay
9%4245%35%5%5%8%45%
2315
September1st to 15thDay
17%4234245%5%6%42%
2160
16th to endDay
16%5%14323446%47%
1911
October1st to 15thDay
19%9%35%424346%35%
1650
16th to endDay
25%9%37%6%44435%25%
1650
November1st to 15thDay
16%8%36%5%35%45%7%33%
1548
16th to endDay
24%12%47%6%23336%26%
1440
December1st to 15thDay
23%14%5%7%6%35%445%18%
1440
16th to endDay
24%15%5%8%6%2442420%
1536
January1st to 15thNight
20%14%6%10%5%3433420%
2506
16th to endNight
15%15%5%7%6%35%445%26%
2667
February1st to 15thNight
13%12%7%11%8%36%5%45%23%
2285
16th to endNight
17%11%5%7%5%345%4428%
1929
March1st to 15thNight
20%10%48%7%3433429%
2114
16th to endNight
15%9%35%42334441%
2016
April1st to 15thNight
25%8%24423345%34%
1796
16th to endNight
19%8%26%424336%38%
1725
May1st to 15thNight
22%8%25%423445%36%
1440
16th to endNight
17%7%2443445%6%38%
1495
June1st to 15thNight
19%6%36%4245%6%8%30%
1440
16th to endNight
17%5%145%25%5%7%7%37%
1440
July1st to 15thNight
10%324435%47%7%46%
1440
16th to endNight
9%5%24435%5%5%8%44%
1514
August1st to 15thNight
10%5%35%6%345%7%9%39%
1491
16th to endNight
10%42442445%7%49%
1875
September1st to 15thNight
14%6%15%6%345%5%6%41%
1800
16th to endNight
16%313423346%49%
1859
October1st to 15thNight
19%8%25%334447%36%
1980
16th to endNight
24%9%36%6%3445%5%28%
2221
November1st to 15thNight
20%8%36%5%34345%33%
2310
16th to endNight
22%10%47%6%35%445%25%
2520
December1st to 15thNight
22%14%5%7%5%3444422%
2520
16th to endNight
25%16%5%7%6%2344420%
2688

Percentage Cloud Cover SE (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
23%14%6%9%6%24345%21%
1432
16th to endDay
14%15%5%8%6%35%45%6%24%
1554
February1st to 15thDay
14%12%411%7%35%445%25%
1575
16th to endDay
18%12%5%6%7%44446%25%
1543
March1st to 15thDay
18%10%5%7%7%35%44427%
1833
16th to endDay
18%6%35%5%23345%40%
2207
April1st to 15thDay
23%9%35%423335%34%
2152
16th to endDay
20%7%46%5%23346%35%
2243
May1st to 15thDay
21%6%35%6%35%446%34%
2511
16th to endDay
20%6%25%5%3445%6%35%
2618
June1st to 15thDay
22%6%25%5%345%5%7%30%
2520
16th to endDay
19%425%5%36%6%7%7%31%
2520
July1st to 15thDay
13%5%246%35%5%7%8%37%
2520
16th to endDay
11%5%35%5%35%6%7%8%36%
2654
August1st to 15thDay
13%5%25%6%35%5%6%8%37%
2466
16th to endDay
10%5%245%35%5%6%7%45%
2315
September1st to 15thDay
16%42433346%7%42%
2160
16th to endDay
16%5%24323346%47%
1911
October1st to 15thDay
20%7%34424346%35%
1650
16th to endDay
25%9%37%6%34445%25%
1650
November1st to 15thDay
16%7%46%5%35%46%6%33%
1548
16th to endDay
23%12%47%5%24345%27%
1440
December1st to 15thDay
24%14%48%6%36%5%45%18%
1440
16th to endDay
24%15%5%7%7%2333420%
1536
January1st to 15thNight
20%15%5%10%6%3444420%
2506
16th to endNight
15%15%5%8%6%35%345%26%
2667
February1st to 15thNight
14%12%6%11%8%35%5%4422%
2278
16th to endNight
17%11%47%5%35%44428%
1929
March1st to 15thNight
20%11%5%7%6%3433429%
2127
16th to endNight
16%8%35%43334442%
2016
April1st to 15thNight
26%8%24424345%34%
1796
16th to endNight
20%7%25%5%23335%39%
1725
May1st to 15thNight
23%7%25%42345%436%
1440
16th to endNight
17%7%25%335%35%6%38%
1495
June1st to 15thNight
20%6%35%5%3446%8%30%
1440
16th to endNight
17%5%245%145%7%9%36%
1440
July1st to 15thNight
10%323425%5%7%9%45%
1440
16th to endNight
10%425%435%5%6%8%44%
1514
August1st to 15thNight
10%426%5%346%7%9%38%
1491
16th to endNight
10%42442446%7%48%
1875
September1st to 15thNight
14%6%15%6%35%447%40%
1800
16th to endNight
16%314423345%48%
1859
October1st to 15thNight
19%7%35%42445%6%36%
1980
16th to endNight
24%8%36%6%34445%28%
2221
November1st to 15thNight
20%9%36%5%34345%33%
2310
16th to endNight
22%11%48%5%35%445%26%
2520
December1st to 15thNight
22%15%5%7%6%24435%21%
2520
16th to endNight
25%16%5%6%5%2444420%
2688

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
66%47%14%5%
1433
16th to endDay
60%412%14%7%
1554
February1st to 15thDay
60%5%12%17%3
1577
16th to endDay
60%410%13%9%1
1543
March1st to 15thDay
59%411%14%8%1
1833
16th to endDay
45%5%9%18%16%5%
2208
April1st to 15thDay
53%37%20%12%2
2152
16th to endDay
50%38%18%14%4
2243
May1st to 15thDay
51%5%7%19%13%1
2511
16th to endDay
47%7%12%19%11%1
2622
June1st to 15thDay
52%5%11%20%9%
2520
16th to endDay
47%8%13%19%10%
2520
July1st to 15thDay
39%7%16%24%11%
2371
16th to endDay
41%8%17%21%9%
2487
August1st to 15thDay
43%9%16%22%9%
2452
16th to endDay
35%7%17%28%10%
2315
September1st to 15thDay
39%6%14%26%12%
2160
16th to endDay
38%5%13%32%10%
1911
October1st to 15thDay
49%412%21%10%
1650
16th to endDay
61%5%12%14%5%
1650
November1st to 15thDay
49%6%15%18%8%
1548
16th to endDay
59%413%15%6%
1440
December1st to 15thDay
66%6%13%11%2
1440
16th to endDay
68%49%10%5%
1536
January1st to 15thNight
67%5%9%11%4
2506
16th to endNight
60%411%15%7%
2667
February1st to 15thNight
62%5%10%17%4
2287
16th to endNight
57%5%8%18%10%
1929
March1st to 15thNight
58%39%18%8%1
2127
16th to endNight
46%49%19%16%4
2016
April1st to 15thNight
52%47%18%15%1
1796
16th to endNight
48%48%18%17%3
1725
May1st to 15thNight
50%47%17%14%5%
1440
16th to endNight
45%5%12%19%14%2
1497
June1st to 15thNight
50%6%13%19%9%
1440
16th to endNight
42%7%13%19%15%
1440
July1st to 15thNight
32%8%14%29%14%
1360
16th to endNight
36%7%15%25%15%
1418
August1st to 15thNight
38%9%18%22%10%
1481
16th to endNight
33%6%17%31%11%
1875
September1st to 15thNight
42%5%12%26%12%
1800
16th to endNight
37%5%12%33%11%
1859
October1st to 15thNight
48%5%11%23%11%
1980
16th to endNight
57%5%13%17%6%
2221
November1st to 15thNight
52%413%17%9%1
2310
16th to endNight
60%6%11%16%4
2520
December1st to 15thNight
65%5%12%13%2
2520
16th to endNight
67%5%9%11%5%
2688

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
30%10%21%25%10%3
60
16th to endDay
29%5%26%31%22
67
February1st to 15thDay
31%6%40%21%1
90
16th to endDay
31%5%26%31%4
202
March1st to 15thDay
24%9%28%27%10%
270
16th to endDay
22%5%26%29%11%5%
288
April1st to 15thDay
29%8%28%18%13%1
270
16th to endDay
19%10%26%22%17%4
270
May1st to 15thDay
28%422%28%10%5%
288
16th to endDay
22%6%29%23%15%3
331
June1st to 15thDay
23%6%23%29%12%5%
315
16th to endDay
19%5%20%31%20%3
315
July1st to 15thDay
14%320%31%21%9%
305
16th to endDay
15%215%33%27%6%
326
August1st to 15thDay
15%311%34%26%8%
313
16th to endDay
12%413%31%23%14%
332
September1st to 15thDay
18%417%18%22%19%
315
16th to endDay
19%5%15%19%23%16%
278
October1st to 15thDay
24%422%25%20%3
255
16th to endDay
31%8%21%26%12%
252
November1st to 15thDay
19%6%21%31%18%2
202
16th to endDay
30%8%21%26%13%
60
December1st to 15thDay
25%338%25%8%
60
16th to endDay
37%10%34%17%
64
January1st to 15thNight
28%7%26%31%5%
720
16th to endNight
22%7%26%33%8%
768
February1st to 15thNight
19%6%34%31%8%
704
16th to endNight
25%429%32%7%
631
March1st to 15thNight
25%8%27%32%5%
720
16th to endNight
20%5%28%34%11%
768
April1st to 15thNight
28%6%27%31%6%
718
16th to endNight
24%6%28%30%9%
645
May1st to 15thNight
28%323%32%10%1
360
16th to endNight
20%426%33%14%
375
June1st to 15thNight
21%323%41%9%
360
16th to endNight
17%123%38%16%1
360
July1st to 15thNight
10%220%46%20%
340
16th to endNight
11%116%46%23%1
376
August1st to 15thNight
15%211%41%26%2
410
16th to endNight
12%217%40%25%2
729
September1st to 15thNight
18%415%38%21%1
720
16th to endNight
18%416%32%25%2
685
October1st to 15thNight
23%5%24%32%14%
660
16th to endNight
28%6%24%30%9%
704
November1st to 15thNight
24%5%25%30%13%
700
16th to endNight
26%9%27%24%11%
720
December1st to 15thNight
31%7%26%27%6%
720
16th to endNight
34%7%29%22%5%1
768
Page generated at 2017-09-23 06:43:46. Version ac04

Copyright 2017 A. Danko


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