Bowen Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bowen Island 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
42%
14498
9%
46776
8%
14470
44%
14470
15%
34988

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
30%
750
9%
2686
8%
746
33%
746
8%
2211
January16th to endNight
33%
783
7%
2757
7%
783
34%
783
9%
2230
February1st to 15thNight
32%
699
6%
2288
4%
699
34%
699
9%
1886
February16th to endNight
36%
632
10%
2053
9%
632
39%
632
14%
1549
March1st to 15thNight
24%
720
4%
2049
3%
720
25%
720
8%
1767
March16th to endNight
29%
768
6%
2082
3%
768
30%
768
10%
1778
April1st to 15thNight
41%
701
8%
1781
5%
701
42%
701
15%
1422
April16th to endNight
43%
513
9%
1593
8%
513
44%
513
13%
1213
May1st to 15thNight
56%
359
11%
1439
18%
359
57%
359
19%
914
May16th to endNight
57%
374
6%
1436
10%
374
58%
374
15%
993
June1st to 15thNight
53%
360
2%
1260
2%
360
54%
360
18%
866
June16th to endNight
57%
360
5%
1260
2%
360
57%
360
18%
859
July1st to 15thNight
73%
340
9%
1190
8%
340
74%
340
36%
633
July16th to endNight
79%
376
14%
1307
21%
354
81%
354
38%
642
August1st to 15thNight
80%
440
15%
1513
20%
438
80%
438
39%
757
August16th to endNight
70%
600
19%
1746
17%
600
71%
600
36%
1010
September1st to 15thNight
75%
720
21%
1800
14%
720
76%
720
44%
1073
September16th to endNight
48%
683
16%
1885
12%
683
49%
683
22%
1346
October1st to 15thNight
49%
660
11%
1980
11%
660
50%
660
21%
1376
October16th to endNight
34%
704
5%
2205
4%
704
36%
704
11%
1758
November1st to 15thNight
24%
700
5%
2450
5%
700
26%
700
6%
2077
November16th to endNight
26%
720
5%
2520
3%
720
30%
720
8%
2044
December1st to 15thNight
29%
736
6%
2616
5%
736
31%
736
8%
2169
December16th to endNight
21%
800
6%
2880
4%
800
24%
800
7%
2415

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
24%6%25%42445%6%33%
48131
Night
28%7%25%423345%30%
46928
Cloud CoverDay
23%7%25%42445%6%32%
48131
Night
28%7%35%423345%30%
46931
TransparencyDay
52%9%15%15%5%1
47786
Night
56%6%13%15%6%1
46777
SeeingDay
22%214%29%25%5%
6214
Night
31%214%24%20%5%
14505

By Month

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
43%9%345%2334316%
1253
16th to endDay
36%9%26%5%24346%18%
1462
February1st to 15thDay
35%9%36%4345%5%418%
1576
16th to endDay
25%8%35%5%25%45%6%25%
1421
March1st to 15thDay
40%9%35%6%2433414%
1910
16th to endDay
32%9%37%6%3424422%
2142
April1st to 15thDay
25%7%37%5%35%5%6%5%22%
2164
16th to endDay
25%7%35%435%45%5%28%
2367
May1st to 15thDay
17%6%247%2445%7%36%
2511
16th to endDay
18%6%36%5%35%5%5%8%30%
2672
June1st to 15thDay
19%6%26%5%25%46%6%33%
2700
16th to endDay
18%6%245%25%45%6%35%
2700
July1st to 15thDay
9%32342335%6%54%
2700
16th to endDay
10%312313346%59%
2771
August1st to 15thDay
9%314313346%58%
2437
16th to endDay
10%31442436%8%49%
2456
September1st to 15thDay
10%32442445%5%53%
2160
16th to endDay
27%413433446%35%
1883
October1st to 15thDay
30%5%24433445%30%
1650
16th to endDay
36%7%25%423346%22%
1663
November1st to 15thDay
46%8%2431333317%
1408
16th to endDay
39%7%35%33334420%
1440
December1st to 15thDay
32%11%46%33433321%
1341
16th to endDay
45%8%3442322416%
1344
January1st to 15thNight
40%9%25%42333421%
2686
16th to endNight
35%8%35%5%2335%6%20%
2757
February1st to 15thNight
36%9%34423445%20%
2276
16th to endNight
26%9%35%5%23345%29%
2053
March1st to 15thNight
40%8%45%5%2334417%
2049
16th to endNight
34%8%36%6%3444419%
2078
April1st to 15thNight
24%9%35%6%35%46%6%24%
1781
16th to endNight
23%9%35%6%35%35%5%27%
1593
May1st to 15thNight
17%3246%3447%7%38%
1439
16th to endNight
16%7%36%5%35%45%8%34%
1436
June1st to 15thNight
19%6%36%434345%37%
1260
16th to endNight
15%6%36%6%35%5%45%36%
1260
July1st to 15thNight
8%323423346%58%
1260
16th to endNight
7%213213445%61%
1397
August1st to 15thNight
6%21322335%6%60%
1521
16th to endNight
9%32442245%7%52%
1746
September1st to 15thNight
8%21332335%5%61%
1800
16th to endNight
24%6%25%323346%37%
1885
October1st to 15thNight
24%5%1442335%6%38%
1980
16th to endNight
38%6%24424345%24%
2205
November1st to 15thNight
43%8%25%5%3323417%
2450
16th to endNight
37%7%25%6%2433323%
2520
December1st to 15thNight
35%11%36%42343420%
2616
16th to endNight
42%10%25%42222320%
2880

Percentage Cloud Cover SW (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
43%8%35%42434416%
1253
16th to endDay
35%9%26%5%25%44419%
1462
February1st to 15thDay
34%10%26%43445%5%18%
1576
16th to endDay
24%10%35%43447%6%24%
1421
March1st to 15thDay
39%11%35%6%2443415%
1910
16th to endDay
31%9%37%6%3434420%
2142
April1st to 15thDay
24%9%37%5%35%5%7%6%21%
2164
16th to endDay
25%7%45%435%45%6%27%
2367
May1st to 15thDay
17%5%35%6%3445%7%35%
2511
16th to endDay
17%7%37%5%35%5%6%8%29%
2672
June1st to 15thDay
18%6%37%42446%7%32%
2700
16th to endDay
18%6%25%5%3446%7%34%
2700
July1st to 15thDay
9%41332345%6%54%
2700
16th to endDay
9%31321335%6%58%
2771
August1st to 15thDay
8%31431335%5%57%
2437
16th to endDay
9%42442336%8%50%
2456
September1st to 15thDay
9%42442345%6%51%
2160
16th to endDay
27%5%1343435%6%34%
1883
October1st to 15thDay
30%6%25%43345%5%29%
1650
16th to endDay
35%7%36%42335%6%21%
1663
November1st to 15thDay
46%7%35%413335%16%
1408
16th to endDay
39%7%45%42344420%
1440
December1st to 15thDay
32%12%5%5%32343321%
1341
16th to endDay
44%10%25%41323415%
1344
January1st to 15thNight
39%10%3432334421%
2685
16th to endNight
34%9%35%42345%5%21%
2757
February1st to 15thNight
36%8%45%424435%20%
2276
16th to endNight
26%9%45%423345%29%
2053
March1st to 15thNight
40%9%45%5%2333416%
2049
16th to endNight
34%9%37%6%2444419%
2082
April1st to 15thNight
24%10%36%5%345%5%7%23%
1781
16th to endNight
23%9%36%5%36%45%5%26%
1593
May1st to 15thNight
17%4245%345%5%7%38%
1439
16th to endNight
15%8%36%5%35%5%6%7%33%
1436
June1st to 15thNight
19%7%35%434436%37%
1260
16th to endNight
15%7%35%6%35%5%5%5%36%
1260
July1st to 15thNight
8%314322346%59%
1260
16th to endNight
6%213313446%62%
1397
August1st to 15thNight
6%31232345%7%60%
1521
16th to endNight
8%42432335%8%51%
1746
September1st to 15thNight
7%222323345%61%
1800
16th to endNight
24%6%25%423346%37%
1885
October1st to 15thNight
24%5%2431435%5%39%
1980
16th to endNight
37%6%25%323445%23%
2205
November1st to 15thNight
43%8%35%5%2332317%
2450
16th to endNight
36%9%26%5%2423422%
2520
December1st to 15thNight
35%12%35%5%2433420%
2616
16th to endNight
41%10%35%41332318%
2880

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
71%7%6%8%5%
1253
16th to endDay
68%8%9%9%11
1462
February1st to 15thDay
68%7%10%6%32
1576
16th to endDay
58%10%13%11%5%
1421
March1st to 15thDay
73%7%10%6%1
1910
16th to endDay
67%7%12%10%1
2142
April1st to 15thDay
61%11%14%11%2
2164
16th to endDay
57%9%15%12%4
2367
May1st to 15thDay
47%10%17%18%6%
2511
16th to endDay
51%12%17%15%2
2676
June1st to 15thDay
48%11%20%13%41
2700
16th to endDay
47%12%19%14%5%
2700
July1st to 15thDay
29%10%19%24%12%2
2541
16th to endDay
25%11%22%28%11%1
2598
August1st to 15thDay
29%10%19%28%10%2
2420
16th to endDay
32%10%22%26%6%1
2456
September1st to 15thDay
33%10%15%22%15%2
2160
16th to endDay
52%9%14%15%6%1
1883
October1st to 15thDay
55%10%15%12%6%
1650
16th to endDay
65%9%13%8%2
1663
November1st to 15thDay
70%7%11%6%11
1408
16th to endDay
69%6%9%9%5%
1440
December1st to 15thDay
68%6%7%9%6%1
1341
16th to endDay
75%38%8%21
1344
January1st to 15thNight
67%7%7%11%5%
2686
16th to endNight
65%7%9%11%31
2757
February1st to 15thNight
66%8%10%9%32
2288
16th to endNight
57%6%13%15%5%
2053
March1st to 15thNight
71%6%10%9%2
2049
16th to endNight
69%6%10%12%1
2082
April1st to 15thNight
60%6%13%15%3
1781
16th to endNight
59%6%13%14%5%
1593
May1st to 15thNight
44%7%19%18%9%
1440
16th to endNight
49%8%19%17%4
1436
June1st to 15thNight
49%6%20%16%5%1
1260
16th to endNight
48%7%18%18%5%1
1260
July1st to 15thNight
28%5%17%30%14%3
1190
16th to endNight
22%7%20%31%14%2
1307
August1st to 15thNight
23%7%23%28%14%3
1513
16th to endNight
29%6%22%27%10%2
1746
September1st to 15thNight
24%8%17%26%19%4
1800
16th to endNight
48%6%14%21%7%2
1885
October1st to 15thNight
48%5%17%18%9%
1980
16th to endNight
62%7%15%10%3
2205
November1st to 15thNight
72%6%10%6%21
2450
16th to endNight
67%6%10%9%6%
2520
December1st to 15thNight
69%6%8%9%4
2616
16th to endNight
71%5%8%8%4
2880

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
18%5%10%23%31%11%
60
16th to endDay
52%211%24%7%1
85
February1st to 15thDay
43%212%23%18%
236
16th to endDay
30%323%20%17%4
211
March1st to 15thDay
44%422%19%7%1
270
16th to endDay
37%322%22%11%1
288
April1st to 15thDay
29%323%21%20%2
269
16th to endDay
25%219%35%12%3
270
May1st to 15thDay
19%221%29%23%2
288
16th to endDay
15%312%29%30%8%
387
June1st to 15thDay
15%213%38%26%4
495
16th to endDay
18%14%35%26%5%
495
July1st to 15thDay
9%27%33%40%6%
475
16th to endDay
6%9%32%43%7%
440
August1st to 15thDay
9%7%27%39%14%
315
16th to endDay
9%11%34%34%9%
332
September1st to 15thDay
13%115%33%25%10%
315
16th to endDay
25%116%27%20%8%
280
October1st to 15thDay
36%16%25%16%3
255
16th to endDay
38%315%23%15%3
204
November1st to 15thDay
51%11%18%13%5%
60
16th to endDay
48%10%11%16%13%
60
December1st to 15thDay
53%116%16%10%1
60
16th to endDay
39%417%26%9%3
64
January1st to 15thNight
45%215%18%15%2
750
16th to endNight
39%217%23%16%1
783
February1st to 15thNight
39%314%26%14%1
704
16th to endNight
31%320%26%14%3
632
March1st to 15thNight
43%318%20%11%2
720
16th to endNight
39%218%23%12%4
768
April1st to 15thNight
30%215%30%16%4
701
16th to endNight
30%314%30%17%4
513
May1st to 15thNight
19%114%30%26%8%
360
16th to endNight
17%310%29%34%5%
375
June1st to 15thNight
20%112%27%29%7%
360
16th to endNight
19%28%34%30%5%
360
July1st to 15thNight
10%7%27%41%12%
340
16th to endNight
7%6%21%47%15%
376
August1st to 15thNight
9%219%46%20%
440
16th to endNight
12%18%21%43%12%
600
September1st to 15thNight
9%17%26%37%17%
720
16th to endNight
28%112%23%23%9%
683
October1st to 15thNight
27%215%27%21%5%
660
16th to endNight
40%314%22%15%3
704
November1st to 15thNight
48%317%25%6%
700
16th to endNight
41%319%20%11%4
720
December1st to 15thNight
41%416%25%10%
736
16th to endNight
47%420%20%6%
800
Page generated at 2017-09-23 03:43:45. Version ac04

Copyright 2017 A. Danko


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