Grasslands National Park East Block
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grasslands National Park East Block clear sky chart from 2005-11-05 to 2017-09-17.

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
35%
15771
16%
46681
9%
15733
42%
15733
23%
30093

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
27%
895
13%
2665
6%
895
33%
895
16%
1871
January16th to endNight
23%
960
15%
2688
6%
960
32%
960
16%
1922
February1st to 15thNight
33%
724
12%
2312
8%
724
39%
724
18%
1575
February16th to endNight
34%
632
14%
2007
9%
632
40%
632
17%
1434
March1st to 15thNight
32%
720
15%
2103
8%
720
41%
720
22%
1418
March16th to endNight
29%
699
13%
2043
7%
699
36%
699
17%
1470
April1st to 15thNight
34%
539
16%
1798
10%
539
43%
539
21%
1132
April16th to endNight
31%
540
17%
1595
8%
540
40%
540
21%
1050
May1st to 15thNight
41%
540
16%
1440
8%
540
45%
540
29%
892
May16th to endNight
34%
563
10%
1498
4%
561
38%
561
20%
1043
June1st to 15thNight
36%
402
7%
1302
4%
402
40%
402
25%
782
June16th to endNight
45%
360
7%
1260
7%
360
49%
360
31%
642
July1st to 15thNight
45%
340
10%
1190
6%
340
50%
340
34%
597
July16th to endNight
48%
541
19%
1393
10%
508
58%
508
47%
712
August1st to 15thNight
58%
539
19%
1456
12%
536
64%
536
44%
792
August16th to endNight
56%
573
28%
1793
19%
573
66%
573
41%
914
September1st to 15thNight
52%
540
21%
1800
18%
540
59%
540
32%
959
September16th to endNight
49%
563
27%
1817
23%
563
56%
563
36%
976
October1st to 15thNight
35%
660
23%
1980
12%
660
45%
660
28%
1193
October16th to endNight
36%
806
20%
2214
9%
806
43%
806
27%
1424
November1st to 15thNight
28%
875
18%
2428
8%
875
36%
875
24%
1606
November16th to endNight
25%
900
16%
2520
5%
900
35%
900
20%
1709
December1st to 15thNight
27%
900
10%
2520
5%
900
31%
900
14%
1939
December16th to endNight
25%
960
14%
2859
5%
960
33%
960
15%
2041

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
9%7%36%6%35%5%6%8%38%
48120
Night
7%7%36%6%35%5%6%8%39%
46839
Cloud CoverDay
9%7%36%6%35%5%6%8%38%
48121
Night
7%7%36%6%35%5%6%8%39%
46841
TransparencyDay
43%415%24%10%1
47782
Night
41%416%24%11%1
46681
SeeingDay
12%15%25%27%15%3
6152
Night
9%20%27%29%11%1
15780

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
6%11%5%11%7%5%8%46%8%24%
1271
16th to endDay
39%5%8%9%5%7%7%9%9%25%
1536
February1st to 15thDay
6%11%6%10%10%6%7%5%5%5%22%
1562
16th to endDay
5%11%7%11%10%46%6%5%7%21%
1467
March1st to 15thDay
5%8%410%8%5%6%6%7%8%28%
1854
16th to endDay
7%11%48%6%35%6%5%11%27%
2180
April1st to 15thDay
9%8%45%6%35%6%6%9%33%
2150
16th to endDay
14%9%36%5%35%45%7%33%
2364
May1st to 15thDay
13%7%35%5%25%35%8%39%
2511
16th to endDay
19%6%345%36%45%8%31%
2616
June1st to 15thDay
15%6%25%5%35%46%8%34%
2655
16th to endDay
8%424435%6%6%9%44%
2700
July1st to 15thDay
5%213435%5%6%9%52%
2700
16th to endDay
42332436%7%59%
2677
August1st to 15thDay
7%4144245%5%9%49%
2493
16th to endDay
7%31331336%7%57%
2408
September1st to 15thDay
10%5%24424446%50%
2160
16th to endDay
14%5%1322235%7%50%
1847
October1st to 15thDay
11%8%26%5%2435%7%42%
1650
16th to endDay
7%9%35%5%345%5%7%41%
1647
November1st to 15thDay
6%9%46%5%35%45%8%41%
1430
16th to endDay
5%8%5%8%7%37%5%5%8%32%
1440
December1st to 15thDay
7%10%5%12%11%5%9%5%6%5%20%
1440
16th to endDay
411%5%13%10%6%8%7%6%6%19%
1362
January1st to 15thNight
5%9%5%9%6%46%7%6%8%29%
2665
16th to endNight
38%48%9%5%7%6%7%8%30%
2688
February1st to 15thNight
6%10%5%7%7%45%5%7%8%30%
2301
16th to endNight
6%10%6%9%8%46%5%5%7%28%
2007
March1st to 15thNight
5%7%47%6%45%5%7%9%35%
2103
16th to endNight
7%9%39%7%5%7%6%6%9%27%
2040
April1st to 15thNight
9%7%35%5%35%5%5%8%40%
1798
16th to endNight
10%8%35%5%3446%8%37%
1595
May1st to 15thNight
8%7%244235%5%9%44%
1439
16th to endNight
15%5%26%6%35%5%6%8%35%
1498
June1st to 15thNight
12%5%2443347%8%42%
1302
16th to endNight
7%2143245%5%8%53%
1260
July1st to 15thNight
432442345%9%55%
1260
16th to endNight
311233346%9%59%
1488
August1st to 15thNight
422432345%8%58%
1464
16th to endNight
7%212323347%61%
1793
September1st to 15thNight
9%32442445%6%54%
1800
16th to endNight
10%31232345%7%54%
1817
October1st to 15thNight
10%6%25%43445%7%46%
1980
16th to endNight
7%8%36%5%35%5%6%8%40%
2214
November1st to 15thNight
7%8%46%6%345%5%7%40%
2428
16th to endNight
5%9%48%6%45%5%5%8%35%
2520
December1st to 15thNight
5%11%6%10%10%6%7%6%6%7%22%
2520
16th to endNight
6%10%49%8%5%5%7%6%8%27%
2859

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
6%11%5%11%7%5%7%5%6%8%24%
1271
16th to endDay
39%5%7%7%5%7%8%10%8%25%
1536
February1st to 15thDay
7%10%6%10%10%6%6%5%5%6%22%
1562
16th to endDay
5%11%7%11%8%47%6%6%7%20%
1467
March1st to 15thDay
5%8%5%11%8%6%5%5%6%9%27%
1854
16th to endDay
8%10%5%10%6%35%5%6%11%27%
2181
April1st to 15thDay
9%9%35%6%35%6%6%9%32%
2150
16th to endDay
14%9%37%5%35%5%47%33%
2364
May1st to 15thDay
14%7%36%5%25%45%8%38%
2511
16th to endDay
19%7%25%5%45%45%7%30%
2616
June1st to 15thDay
15%7%25%6%35%5%5%8%34%
2655
16th to endDay
9%5%24435%6%6%8%43%
2700
July1st to 15thDay
5%3144346%6%9%51%
2700
16th to endDay
431232346%7%59%
2677
August1st to 15thDay
8%4144345%5%8%48%
2493
16th to endDay
7%313323348%56%
2408
September1st to 15thDay
10%5%24435%446%49%
2160
16th to endDay
14%5%1232335%7%50%
1847
October1st to 15thDay
12%7%36%434346%42%
1650
16th to endDay
7%10%35%5%35%5%6%6%40%
1647
November1st to 15thDay
6%9%5%6%6%2436%7%41%
1430
16th to endDay
6%9%48%8%27%6%5%8%33%
1440
December1st to 15thDay
5%11%6%12%11%48%6%6%6%20%
1440
16th to endDay
410%5%11%11%7%7%7%7%5%19%
1362
January1st to 15thNight
6%8%5%9%5%37%7%7%8%30%
2665
16th to endNight
38%49%8%5%7%6%7%8%29%
2688
February1st to 15thNight
5%11%47%6%45%5%7%9%30%
2301
16th to endNight
6%10%6%9%9%5%5%6%6%9%26%
2007
March1st to 15thNight
5%7%47%6%37%6%8%9%33%
2103
16th to endNight
8%9%49%8%47%46%8%28%
2043
April1st to 15thNight
8%8%36%445%5%6%7%39%
1798
16th to endNight
10%8%36%5%4446%7%37%
1595
May1st to 15thNight
8%8%244235%6%7%45%
1439
16th to endNight
14%7%35%5%36%5%5%8%35%
1497
June1st to 15thNight
12%42442447%8%42%
1302
16th to endNight
7%31433445%8%53%
1260
July1st to 15thNight
5%31342345%8%55%
1260
16th to endNight
321242446%8%59%
1488
August1st to 15thNight
4313323448%58%
1464
16th to endNight
7%213214346%61%
1793
September1st to 15thNight
9%41433335%6%54%
1800
16th to endNight
10%41232345%7%54%
1817
October1st to 15thNight
10%6%25%42436%7%45%
1980
16th to endNight
6%9%35%5%345%7%8%38%
2214
November1st to 15thNight
8%8%45%6%3446%7%40%
2428
16th to endNight
5%8%5%8%6%45%5%6%8%34%
2520
December1st to 15thNight
5%11%5%10%10%5%6%7%7%6%22%
2520
16th to endNight
6%10%49%8%45%6%7%7%28%
2859

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
55%6%11%19%6%
1271
16th to endDay
48%8%18%17%5%
1536
February1st to 15thDay
60%5%12%14%6%
1562
16th to endDay
59%314%14%7%
1467
March1st to 15thDay
52%7%19%16%3
1854
16th to endDay
51%5%19%19%3
2181
April1st to 15thDay
46%5%18%20%8%
2150
16th to endDay
49%316%22%7%
2364
May1st to 15thDay
45%213%28%9%
2511
16th to endDay
51%414%20%8%
2620
June1st to 15thDay
47%317%21%9%
2655
16th to endDay
35%418%31%8%
2700
July1st to 15thDay
27%317%32%16%2
2541
16th to endDay
23%213%34%21%4
2509
August1st to 15thDay
32%215%29%14%3
2477
16th to endDay
25%212%37%19%3
2408
September1st to 15thDay
36%212%29%16%3
2160
16th to endDay
34%311%32%17%2
1847
October1st to 15thDay
42%316%27%9%
1650
16th to endDay
42%419%27%6%
1647
November1st to 15thDay
40%5%18%24%10%1
1430
16th to endDay
47%6%20%16%7%
1440
December1st to 15thDay
62%7%13%15%1
1440
16th to endDay
60%5%16%13%3
1362
January1st to 15thNight
47%7%18%21%3
2665
16th to endNight
49%6%16%20%5%1
2688
February1st to 15thNight
48%418%20%6%1
2312
16th to endNight
53%414%19%8%
2007
March1st to 15thNight
43%5%18%24%7%
2103
16th to endNight
53%316%21%4
2043
April1st to 15thNight
41%5%16%25%10%1
1798
16th to endNight
44%313%25%11%1
1595
May1st to 15thNight
35%412%33%14%
1440
16th to endNight
47%414%24%9%
1498
June1st to 15thNight
37%418%25%12%1
1302
16th to endNight
27%324%31%11%1
1260
July1st to 15thNight
26%316%30%20%3
1190
16th to endNight
20%216%33%22%4
1393
August1st to 15thNight
23%315%36%18%1
1456
16th to endNight
24%39%29%28%5%
1793
September1st to 15thNight
31%111%29%19%5%
1800
16th to endNight
28%310%30%23%2
1817
October1st to 15thNight
36%314%28%15%1
1980
16th to endNight
40%316%27%10%1
2214
November1st to 15thNight
42%317%23%10%2
2428
16th to endNight
45%420%20%8%
2520
December1st to 15thNight
58%5%15%16%3
2520
16th to endNight
50%6%16%20%6%
2859

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%6%23%30%28%4
63
16th to endDay
12%6%29%27%21%3
96
February1st to 15thDay
11%12%40%26%8%1
90
16th to endDay
12%335%32%13%2
81
March1st to 15thDay
15%15%31%27%9%
144
16th to endDay
10%20%35%21%8%3
288
April1st to 15thDay
10%28%26%26%6%1
269
16th to endDay
21%19%21%26%9%1
342
May1st to 15thDay
13%18%22%24%16%4
468
16th to endDay
19%18%19%21%14%7%
517
June1st to 15thDay
13%17%28%23%14%2
495
16th to endDay
11%18%22%30%15%1
495
July1st to 15thDay
8%12%22%33%20%2
475
16th to endDay
6%16%24%30%19%3
515
August1st to 15thDay
9%10%22%27%21%8%
466
16th to endDay
8%12%19%30%21%7%
332
September1st to 15thDay
13%10%28%30%11%5%
315
16th to endDay
19%7%23%29%15%3
178
October1st to 15thDay
23%5%31%26%10%3
90
16th to endDay
13%8%23%27%22%4
96
November1st to 15thDay
8%238%33%15%1
90
16th to endDay
10%10%43%22%13%1
90
December1st to 15thDay
46%41%25%16%5%
90
16th to endDay
16%7%43%20%8%2
67
January1st to 15thNight
8%25%30%24%10%1
900
16th to endNight
7%27%31%24%8%1
960
February1st to 15thNight
8%21%25%29%13%1
728
16th to endNight
9%19%23%31%13%2
632
March1st to 15thNight
7%22%30%27%10%2
720
16th to endNight
10%22%27%30%8%1
699
April1st to 15thNight
10%23%26%32%6%
539
16th to endNight
13%21%27%28%7%
540
May1st to 15thNight
9%22%22%29%14%1
540
16th to endNight
16%23%18%26%14%1
563
June1st to 15thNight
11%21%24%29%10%1
402
16th to endNight
8%20%23%33%14%
360
July1st to 15thNight
7%14%29%32%14%1
340
16th to endNight
319%25%38%12%
541
August1st to 15thNight
6%11%20%41%18%2
539
16th to endNight
8%12%19%37%20%1
573
September1st to 15thNight
10%11%20%39%16%1
540
16th to endNight
9%12%25%37%13%1
563
October1st to 15thNight
13%13%30%28%12%1
660
16th to endNight
9%16%31%32%10%
806
November1st to 15thNight
11%22%31%24%8%1
875
16th to endNight
7%25%34%26%5%
900
December1st to 15thNight
8%21%29%27%11%1
900
16th to endNight
10%21%29%25%10%1
960
Page generated at 2017-09-18 06:38:23. Version ac04

Copyright 2017 A. Danko


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