Rocky Harbour
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rocky Harbour clear sky chart from 2005-11-05 to 2017-12-01.

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
19%
15443
4%
47778
3%
15401
21%
15401
7%
41356

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
6%
747
2%
2536
1%
746
7%
746
1%
2423
January16th to endNight
10%
800
3%
2688
2%
800
10%
800
2%
2517
February1st to 15thNight
9%
724
1%
2411
1%
722
9%
722
2%
2282
February16th to endNight
16%
631
1%
1922
0%
631
16%
631
4%
1724
March1st to 15thNight
16%
717
5%
2148
2%
716
18%
716
6%
1887
March16th to endNight
17%
618
6%
2007
4%
618
21%
618
6%
1739
April1st to 15thNight
19%
539
5%
1796
4%
539
20%
539
6%
1532
April16th to endNight
25%
540
9%
1595
7%
540
27%
540
11%
1287
May1st to 15thNight
34%
540
8%
1440
4%
540
35%
540
17%
1100
May16th to endNight
27%
561
5%
1411
2%
560
29%
560
13%
1149
June1st to 15thNight
33%
540
3%
1260
2%
540
34%
540
14%
1051
June16th to endNight
30%
540
2%
1260
1%
540
31%
540
18%
1008
July1st to 15thNight
34%
510
2%
1254
2%
510
34%
510
17%
977
July16th to endNight
35%
565
5%
1419
3%
532
37%
532
15%
1129
August1st to 15thNight
35%
539
5%
1429
2%
535
37%
535
15%
1137
August16th to endNight
34%
573
7%
1780
6%
573
36%
573
14%
1357
September1st to 15thNight
25%
540
6%
1800
4%
540
28%
540
10%
1428
September16th to endNight
18%
538
7%
1980
5%
538
22%
538
8%
1570
October1st to 15thNight
17%
681
7%
2138
3%
681
20%
681
7%
1786
October16th to endNight
17%
816
6%
2496
3%
816
19%
816
7%
2139
November1st to 15thNight
15%
805
5%
2537
2%
805
17%
805
5%
2270
November16th to endNight
10%
825
3%
2880
2%
825
12%
825
3%
2615
December1st to 15thNight
7%
754
2%
2711
0%
754
9%
754
2%
2536
December16th to endNight
10%
800
2%
2880
2%
800
10%
800
2%
2713

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%13%5%8%7%34345%20%
48644
Night
23%16%6%10%8%3333415%
47958
TransparencyDay
69%5%9%10%3
48329
Night
74%5%8%8%2
47792
SeeingDay
32%14%24%18%7%2
8273
Night
31%16%23%19%7%1
15450

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
15%21%14%19%11%422223
1399
16th to endDay
11%20%11%17%18%6%5%1113
1536
February1st to 15thDay
13%15%9%18%17%6%5%2224
1448
16th to endDay
13%20%9%14%12%45%22211%
1551
March1st to 15thDay
15%17%7%11%11%5%5%32315%
1790
16th to endDay
17%18%7%10%9%4343415%
2215
April1st to 15thDay
22%16%6%7%7%34335%17%
2153
16th to endDay
18%11%5%7%5%23346%29%
2364
May1st to 15thDay
24%9%35%5%24346%29%
2512
16th to endDay
29%10%36%434445%23%
2699
June1st to 15thDay
26%7%36%6%3445%7%23%
2700
16th to endDay
27%8%36%5%25%345%27%
2700
July1st to 15thDay
26%7%2442345%6%30%
2628
16th to endDay
29%7%35%5%34446%25%
2653
August1st to 15thDay
22%8%36%5%35%35%7%29%
2520
16th to endDay
31%6%24323448%27%
2420
September1st to 15thDay
30%8%35%423445%26%
2160
16th to endDay
32%9%25%5%2345%7%22%
1980
October1st to 15thDay
31%11%36%424335%23%
1821
16th to endDay
35%20%36%5%2332313%
1728
November1st to 15thDay
28%26%5%6%42332412%
1650
16th to endDay
23%27%9%11%32222311%
1410
December1st to 15thDay
18%23%11%18%9%212135%
1263
16th to endDay
18%23%10%14%13%421226%
1344
January1st to 15thNight
15%24%11%16%12%332124
2536
16th to endNight
13%17%9%18%16%7%42225%
2688
February1st to 15thNight
14%16%8%17%19%7%42224
2411
16th to endNight
12%17%8%20%10%3433312%
1922
March1st to 15thNight
17%13%7%14%10%6%432314%
2147
16th to endNight
16%21%8%10%8%33235%15%
2007
April1st to 15thNight
22%20%7%10%5%23335%15%
1796
16th to endNight
17%12%5%8%6%35%347%25%
1595
May1st to 15thNight
23%10%35%6%23346%31%
1440
16th to endNight
30%8%35%5%33445%24%
1410
June1st to 15thNight
24%8%46%5%36%5%5%7%22%
1260
16th to endNight
28%8%35%5%23447%26%
1260
July1st to 15thNight
30%6%35%423346%28%
1329
16th to endNight
30%6%25%5%25%45%6%23%
1515
August1st to 15thNight
26%7%36%5%3345%6%26%
1440
16th to endNight
29%6%25%43345%7%28%
1780
September1st to 15thNight
35%7%26%5%2433423%
1800
16th to endNight
34%8%35%424445%21%
1980
October1st to 15thNight
31%13%47%5%3344418%
2138
16th to endNight
33%20%46%42223415%
2496
November1st to 15thNight
28%24%6%6%43322413%
2537
16th to endNight
25%27%11%8%4222238%
2880
December1st to 15thNight
22%23%10%16%9%221127%
2711
16th to endNight
17%22%13%14%10%322226%
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
88%432
1400
16th to endDay
90%3221
1536
February1st to 15thDay
86%35%31
1451
16th to endDay
81%436%3
1551
March1st to 15thDay
73%5%7%8%4
1800
16th to endDay
76%5%6%6%5%
2215
April1st to 15thDay
73%47%10%3
2153
16th to endDay
61%6%9%14%8%
2364
May1st to 15thDay
58%7%10%16%7%
2512
16th to endDay
65%5%12%12%4
2703
June1st to 15thDay
64%8%12%11%2
2700
16th to endDay
61%6%12%14%5%
2700
July1st to 15thDay
54%7%15%18%3
2476
16th to endDay
61%6%12%15%3
2486
August1st to 15thDay
57%7%17%15%2
2506
16th to endDay
59%6%15%14%3
2420
September1st to 15thDay
62%5%13%14%3
2160
16th to endDay
63%6%13%12%4
1980
October1st to 15thDay
66%49%13%5%
1821
16th to endDay
78%46%7%2
1728
November1st to 15thDay
80%47%6%
1650
16th to endDay
82%45%5%1
1410
December1st to 15thDay
88%441
1263
16th to endDay
87%3331
1344
January1st to 15thNight
88%5%32
2536
16th to endNight
86%3332
2688
February1st to 15thNight
88%433
2412
16th to endNight
78%7%6%5%3
1922
March1st to 15thNight
74%6%6%9%2
2160
16th to endNight
75%5%7%8%3
2007
April1st to 15thNight
74%5%7%10%2
1796
16th to endNight
63%7%9%11%8%
1595
May1st to 15thNight
56%5%13%15%8%1
1440
16th to endNight
63%6%10%14%5%
1412
June1st to 15thNight
61%9%9%15%3
1260
16th to endNight
56%8%15%14%5%
1260
July1st to 15thNight
56%7%15%17%3
1254
16th to endNight
59%7%13%16%2
1419
August1st to 15thNight
58%8%17%13%2
1429
16th to endNight
58%7%16%14%4
1780
September1st to 15thNight
64%5%11%15%2
1800
16th to endNight
66%5%12%11%3
1980
October1st to 15thNight
70%6%7%10%5%
2138
16th to endNight
74%49%9%2
2496
November1st to 15thNight
79%45%7%1
2537
16th to endNight
82%45%5%1
2880
December1st to 15thNight
86%45%3
2711
16th to endNight
87%4321
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
20%35%27%12%3
240
16th to endDay
24%25%29%14%41
256
February1st to 15thDay
23%26%29%13%41
236
16th to endDay
23%22%27%13%10%2
212
March1st to 15thDay
25%25%26%12%7%3
240
16th to endDay
28%22%25%17%5%1
281
April1st to 15thDay
34%19%23%15%5%1
270
16th to endDay
26%17%24%19%10%1
438
May1st to 15thDay
30%9%21%24%11%3
468
16th to endDay
34%10%23%19%10%2
519
June1st to 15thDay
32%6%23%25%9%2
495
16th to endDay
34%10%26%18%7%2
495
July1st to 15thDay
32%9%20%23%11%3
475
16th to endDay
35%6%20%23%12%2
514
August1st to 15thDay
29%6%27%22%11%2
493
16th to endDay
34%6%21%23%10%3
437
September1st to 15thDay
44%6%28%15%4
315
16th to endDay
42%14%24%15%21
269
October1st to 15thDay
41%12%22%14%5%2
270
16th to endDay
47%14%16%11%9%1
288
November1st to 15thDay
40%16%22%15%41
280
16th to endDay
32%21%24%15%4
285
December1st to 15thDay
31%25%26%13%3
241
16th to endDay
30%27%23%10%5%2
256
January1st to 15thNight
25%30%27%13%2
750
16th to endNight
24%25%29%15%4
800
February1st to 15thNight
23%27%27%16%5%
725
16th to endNight
22%18%30%18%7%2
631
March1st to 15thNight
22%23%28%19%5%1
720
16th to endNight
24%18%30%19%7%
618
April1st to 15thNight
29%16%23%22%7%1
539
16th to endNight
26%13%26%22%10%1
540
May1st to 15thNight
28%10%19%26%12%2
540
16th to endNight
34%9%22%22%8%1
561
June1st to 15thNight
27%7%22%29%11%
540
16th to endNight
29%7%24%27%9%1
540
July1st to 15thNight
34%6%19%24%14%1
510
16th to endNight
33%8%15%28%12%
565
August1st to 15thNight
30%6%20%27%14%
539
16th to endNight
32%6%21%23%14%1
573
September1st to 15thNight
40%8%20%23%5%
540
16th to endNight
39%11%25%18%4
538
October1st to 15thNight
42%15%20%13%6%1
681
16th to endNight
44%14%18%16%6%
816
November1st to 15thNight
40%17%19%16%6%
805
16th to endNight
38%20%22%13%3
825
December1st to 15thNight
33%23%25%14%2
754
16th to endNight
28%24%25%15%41
800
Page generated at 2017-12-02 10:44:16. Version ac04

Copyright 2017 A. Danko


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