Green River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Green River clear sky chart from 2005-11-05 to 2017-10-06.

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
69%
15852
27%
47226
24%
15815
72%
15815
41%
25980

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
74%
716
21%
2327
22%
716
76%
716
36%
1310
January16th to endNight
67%
768
24%
2496
25%
768
69%
768
30%
1513
February1st to 15thNight
66%
699
16%
2288
17%
699
68%
699
30%
1381
February16th to endNight
60%
632
26%
1923
23%
632
66%
632
33%
1150
March1st to 15thNight
65%
720
29%
1980
25%
720
70%
720
42%
1143
March16th to endNight
59%
768
28%
2112
18%
768
66%
768
42%
1210
April1st to 15thNight
54%
606
23%
1865
17%
606
60%
606
35%
1056
April16th to endNight
55%
540
32%
1689
23%
540
66%
540
39%
898
May1st to 15thNight
56%
540
25%
1619
19%
539
60%
539
35%
915
May16th to endNight
61%
561
25%
1685
20%
561
66%
561
42%
886
June1st to 15thNight
69%
540
28%
1449
24%
540
72%
540
52%
762
June16th to endNight
75%
540
32%
1495
30%
540
77%
540
59%
719
July1st to 15thNight
80%
510
18%
1530
18%
510
81%
510
40%
842
July16th to endNight
82%
564
25%
1593
22%
531
82%
531
42%
861
August1st to 15thNight
77%
539
24%
1611
22%
536
78%
536
41%
881
August16th to endNight
81%
573
33%
1800
32%
573
83%
573
46%
913
September1st to 15thNight
78%
612
32%
1872
30%
612
81%
612
47%
939
September16th to endNight
76%
716
41%
1980
32%
716
81%
716
58%
973
October1st to 15thNight
72%
684
34%
2034
28%
684
75%
684
52%
1001
October16th to endNight
74%
704
36%
2112
30%
704
78%
704
52%
1028
November1st to 15thNight
77%
700
34%
2178
32%
700
80%
700
47%
1095
November16th to endNight
71%
838
32%
2458
29%
838
74%
838
48%
1259
December1st to 15thNight
70%
900
20%
2520
18%
900
73%
900
42%
1435
December16th to endNight
57%
882
14%
2610
12%
882
59%
882
22%
1810

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
331342445%8%56%
47951
Night
442442445%8%55%
47421
TransparencyDay
25%410%22%21%15%
47646
Night
27%410%22%21%13%
47227
SeeingDay
6%6%16%30%29%10%
5578
Night
6%213%41%30%4
15863

By Month

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
4328%8%6%7%6%7%9%36%
1611
16th to endDay
5%4247%5%6%7%7%10%38%
1728
February1st to 15thDay
2415%8%46%6%8%12%38%
1575
16th to endDay
7%5%25%5%2446%8%46%
1546
March1st to 15thDay
34235%2445%8%56%
1980
16th to endDay
441442446%8%53%
2112
April1st to 15thDay
442342445%6%58%
2081
16th to endDay
331342345%6%60%
2269
May1st to 15thDay
4313325%5%5%9%54%
2331
16th to endDay
321342345%8%59%
2429
June1st to 15thDay
3312222346%67%
2505
16th to endDay
111212335%77%
2459
July1st to 15thDay
33134345%7%9%53%
2340
16th to endDay
32144346%8%11%48%
2467
August1st to 15thDay
33134345%6%10%52%
2340
16th to endDay
221222346%8%61%
2402
September1st to 15thDay
421222445%6%62%
2085
16th to endDay
421212236%72%
1980
October1st to 15thDay
5%313213336%66%
1723
16th to endDay
2213213346%67%
1760
November1st to 15thDay
3322313236%66%
1678
16th to endDay
3323312337%65%
1488
December1st to 15thDay
5%6%145%35%47%9%45%
1440
16th to endDay
7%7%37%7%5%6%5%8%10%29%
1622
January1st to 15thNight
5%5%24425%5%6%10%46%
2327
16th to endNight
7%5%16%5%35%45%10%43%
2496
February1st to 15thNight
3426%8%46%45%8%44%
2277
16th to endNight
35%37%6%35%5%5%8%45%
1923
March1st to 15thNight
45%134245%5%8%54%
1980
16th to endNight
45%3432345%7%56%
2112
April1st to 15thNight
6%6%24335%446%53%
1865
16th to endNight
442432345%6%59%
1689
May1st to 15thNight
44345%35%445%54%
1619
16th to endNight
431242445%7%58%
1684
June1st to 15thNight
421231445%7%62%
1449
16th to endNight
2112213346%69%
1495
July1st to 15thNight
3313446%6%8%10%48%
1620
16th to endNight
2214436%7%8%11%47%
1701
August1st to 15thNight
33144446%5%8%52%
1620
16th to endNight
2213425%47%9%56%
1800
September1st to 15thNight
42123235%5%8%61%
1872
16th to endNight
321321222373%
1980
October1st to 15thNight
5%212222346%65%
2034
16th to endNight
441221225%6%66%
2112
November1st to 15thNight
3313324336%64%
2178
16th to endNight
5%312323336%64%
2458
December1st to 15thNight
5%5%2341346%8%53%
2520
16th to endNight
7%7%37%8%45%6%6%10%34%
2610

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
41%9%22%21%5%
1612
16th to endDay
39%6%20%24%8%
1728
February1st to 15thDay
34%9%22%21%10%1
1575
16th to endDay
33%5%10%31%15%2
1546
March1st to 15thDay
26%310%33%19%5%
1980
16th to endDay
27%49%32%21%5%
2112
April1st to 15thDay
27%36%24%28%10%
2081
16th to endDay
23%35%25%28%12%
2269
May1st to 15thDay
25%46%18%30%13%
2331
16th to endDay
21%47%21%29%15%
2432
June1st to 15thDay
17%2314%27%34%
2505
16th to endDay
10%218%22%54%
2459
July1st to 15thDay
23%48%16%16%30%
2201
16th to endDay
25%5%9%19%17%21%
2312
August1st to 15thDay
25%5%9%19%16%23%
2325
16th to endDay
19%47%19%26%22%
2402
September1st to 15thDay
20%38%14%26%26%
2085
16th to endDay
15%26%20%33%21%
1980
October1st to 15thDay
20%26%27%32%9%
1723
16th to endDay
19%310%32%31%3
1760
November1st to 15thDay
20%312%32%27%3
1678
16th to endDay
22%316%39%16%1
1488
December1st to 15thDay
33%8%26%24%7%
1440
16th to endDay
47%10%19%16%5%
1622
January1st to 15thNight
30%5%22%32%8%
2327
16th to endNight
36%5%16%27%11%1
2496
February1st to 15thNight
36%5%18%24%13%2
2288
16th to endNight
35%49%28%19%2
1923
March1st to 15thNight
28%47%30%22%7%
1980
16th to endNight
28%47%27%26%6%
2112
April1st to 15thNight
32%36%18%25%14%
1865
16th to endNight
25%5%423%28%13%
1689
May1st to 15thNight
31%46%13%29%14%
1620
16th to endNight
23%5%6%19%32%13%
1685
June1st to 15thNight
21%3310%25%34%
1449
16th to endNight
15%326%14%57%
1495
July1st to 15thNight
26%6%8%14%13%30%
1530
16th to endNight
24%6%9%20%18%20%
1593
August1st to 15thNight
26%5%11%17%17%21%
1611
16th to endNight
22%5%7%16%24%25%
1800
September1st to 15thNight
21%47%15%16%33%
1872
16th to endNight
17%2317%28%29%
1980
October1st to 15thNight
20%26%22%30%17%
2034
16th to endNight
20%26%20%39%9%
2112
November1st to 15thNight
23%37%27%30%8%
2178
16th to endNight
23%28%31%29%4
2458
December1st to 15thNight
28%420%32%14%
2520
16th to endNight
44%8%20%20%4
2610

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
23%212%31%23%7%
90
16th to endDay
9%28%28%40%11%
96
February1st to 15thDay
12%41%34%12%
90
16th to endDay
11%9%18%32%22%6%
177
March1st to 15thDay
6%12%14%30%28%7%
270
16th to endDay
7%13%22%32%20%2
288
April1st to 15thDay
9%17%25%21%17%7%
269
16th to endDay
11%17%27%25%15%3
270
May1st to 15thDay
8%12%26%29%15%7%
288
16th to endDay
411%19%30%22%11%
330
June1st to 15thDay
5%7%17%31%28%8%
480
16th to endDay
2217%31%33%11%
434
July1st to 15thDay
3117%29%33%14%
305
16th to endDay
319%27%43%13%
327
August1st to 15thDay
4310%33%37%12%
315
16th to endDay
418%25%43%16%
332
September1st to 15thDay
2317%27%34%15%
315
16th to endDay
7%5%14%21%33%17%
315
October1st to 15thDay
412%28%31%22%
125
16th to endDay
6%48%37%33%10%
96
November1st to 15thDay
2115%24%38%17%
90
16th to endDay
6%8%11%54%14%4
90
December1st to 15thDay
10%26%58%20%2
90
16th to endDay
15%413%33%28%5%
96
January1st to 15thNight
8%17%49%26%6%
720
16th to endNight
10%19%43%27%6%
768
February1st to 15thNight
5%111%53%24%4
704
16th to endNight
4318%53%17%2
632
March1st to 15thNight
6%316%46%25%1
720
16th to endNight
6%322%44%20%1
768
April1st to 15thNight
10%7%23%40%16%1
606
16th to endNight
6%8%26%33%22%2
540
May1st to 15thNight
6%5%22%41%21%2
540
16th to endNight
6%5%20%36%28%3
563
June1st to 15thNight
5%318%42%28%2
540
16th to endNight
3113%45%33%2
540
July1st to 15thNight
36%35%51%3
510
16th to endNight
2326%59%6%
564
August1st to 15thNight
5%15%36%46%3
539
16th to endNight
37%31%48%9%
573
September1st to 15thNight
5%8%34%42%7%
612
16th to endNight
5%111%26%43%10%
716
October1st to 15thNight
7%113%42%28%5%
684
16th to endNight
8%111%36%37%4
704
November1st to 15thNight
5%210%44%33%5%
700
16th to endNight
7%312%42%29%5%
838
December1st to 15thNight
9%111%54%21%2
900
16th to endNight
12%212%44%24%3
882
Page generated at 2017-10-07 12:07:52. Version ac04

Copyright 2017 A. Danko


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