Green Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Green Lake clear sky chart from 2005-11-05 to 2017-09-24.

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
40%
14795
10%
46787
8%
14769
43%
14769
17%
33241

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%
748
6%
2686
5%
746
29%
746
8%
2178
January16th to endNight
36%
782
8%
2772
6%
782
39%
782
12%
2077
February1st to 15thNight
35%
696
9%
2369
7%
696
39%
696
13%
1785
February16th to endNight
45%
632
14%
2020
12%
632
50%
632
22%
1345
March1st to 15thNight
33%
720
11%
2122
7%
720
38%
720
17%
1529
March16th to endNight
36%
768
13%
2030
7%
768
39%
768
20%
1473
April1st to 15thNight
41%
719
11%
1799
5%
719
43%
719
20%
1320
April16th to endNight
37%
447
12%
1527
10%
447
41%
447
15%
1095
May1st to 15thNight
37%
359
10%
1440
12%
359
42%
359
15%
977
May16th to endNight
42%
374
5%
1412
3%
374
44%
374
13%
1001
June1st to 15thNight
40%
360
1%
1080
0%
360
40%
360
15%
798
June16th to endNight
41%
360
0%
1080
0%
360
41%
360
20%
770
July1st to 15thNight
56%
340
2%
1141
0%
340
56%
340
27%
687
July16th to endNight
55%
376
8%
1313
9%
354
58%
354
27%
758
August1st to 15thNight
68%
360
16%
1432
24%
358
71%
358
30%
745
August16th to endNight
59%
598
19%
1744
17%
598
61%
598
33%
1035
September1st to 15thNight
58%
720
19%
1800
11%
720
60%
720
38%
1113
September16th to endNight
47%
692
19%
1888
12%
692
51%
692
29%
1235
October1st to 15thNight
46%
660
14%
1980
13%
660
49%
660
22%
1314
October16th to endNight
37%
704
11%
2254
7%
704
42%
704
18%
1583
November1st to 15thNight
31%
700
11%
2450
8%
700
36%
700
13%
1769
November16th to endNight
32%
780
8%
2580
6%
780
35%
780
12%
2000
December1st to 15thNight
33%
917
9%
2805
6%
917
37%
917
11%
2207
December16th to endNight
29%
983
7%
3063
4%
983
33%
983
10%
2447

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%10%48%7%46%5%6%7%29%
48169
Night
8%11%5%9%7%46%5%6%7%28%
46939
TransparencyDay
51%314%20%8%
47824
Night
53%415%19%6%
46788
SeeingDay
16%11%23%25%16%5%
6481
Night
15%9%20%32%18%2
14807

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
9%13%6%14%8%47%6%6%6%15%
1253
16th to endDay
8%12%7%12%9%45%46%5%22%
1452
February1st to 15thDay
8%15%7%10%7%45%5%5%6%23%
1495
16th to endDay
5%12%5%8%8%46%6%6%6%27%
1454
March1st to 15thDay
5%13%6%11%9%48%5%7%8%20%
1836
16th to endDay
5%11%6%10%8%46%6%6%7%24%
2193
April1st to 15thDay
8%15%5%9%8%5%6%5%6%7%20%
2149
16th to endDay
8%12%411%10%5%7%6%6%6%19%
2432
May1st to 15thDay
10%11%5%8%6%46%5%5%7%28%
2511
16th to endDay
15%10%48%9%45%5%6%7%22%
2693
June1st to 15thDay
16%9%48%7%36%5%5%6%24%
2880
16th to endDay
12%8%38%7%46%6%7%7%26%
2880
July1st to 15thDay
7%6%26%5%35%5%7%7%41%
2746
16th to endDay
9%4245%35%5%6%6%45%
2766
August1st to 15thDay
5%5%25%5%35%5%6%8%46%
2520
16th to endDay
8%5%26%6%45%6%6%8%40%
2457
September1st to 15thDay
10%5%15%42345%6%49%
2160
16th to endDay
13%8%37%5%35%5%46%35%
1928
October1st to 15thDay
10%9%37%7%3445%7%36%
1650
16th to endDay
14%12%5%7%6%3446%6%27%
1616
November1st to 15thDay
12%14%5%7%7%45%6%6%6%22%
1408
16th to endDay
8%14%7%10%8%46%6%6%6%20%
1367
December1st to 15thDay
9%14%6%11%10%38%5%6%5%17%
1152
16th to endDay
6%13%7%12%9%47%6%6%7%19%
1171
January1st to 15thNight
11%15%7%13%9%46%5%5%6%13%
2686
16th to endNight
8%12%6%12%9%46%6%6%7%19%
2772
February1st to 15thNight
9%16%7%9%7%35%5%6%5%22%
2357
16th to endNight
5%11%49%7%445%6%7%33%
2020
March1st to 15thNight
5%13%5%9%7%5%6%6%6%7%26%
2122
16th to endNight
39%5%9%7%49%8%6%8%27%
2027
April1st to 15thNight
410%5%9%9%47%6%6%8%28%
1799
16th to endNight
7%13%48%9%37%5%6%6%26%
1527
May1st to 15thNight
9%10%6%9%9%35%46%7%28%
1439
16th to endNight
17%8%48%6%5%5%6%6%8%22%
1412
June1st to 15thNight
16%9%48%7%46%5%6%425%
1080
16th to endNight
11%8%49%7%46%5%6%9%27%
1080
July1st to 15thNight
6%5%27%5%36%6%6%10%39%
1211
16th to endNight
7%426%7%35%6%7%8%38%
1403
August1st to 15thNight
5%425%5%35%5%7%9%46%
1440
16th to endNight
7%425%5%36%5%7%9%40%
1744
September1st to 15thNight
8%6%245%3345%6%49%
1800
16th to endNight
11%8%25%5%245%6%7%39%
1888
October1st to 15thNight
10%8%48%7%3445%6%36%
1980
16th to endNight
12%11%38%6%45%5%5%6%29%
2254
November1st to 15thNight
10%14%5%7%7%35%6%6%7%24%
2450
16th to endNight
9%15%6%10%7%5%5%5%5%7%21%
2580
December1st to 15thNight
9%15%6%10%8%46%5%5%6%20%
2805
16th to endNight
6%15%7%12%9%47%6%5%7%17%
3063

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
64%6%16%9%2
1253
16th to endDay
59%417%12%3
1452
February1st to 15thDay
60%6%14%12%5%
1495
16th to endDay
52%317%17%8%
1454
March1st to 15thDay
59%414%15%5%
1836
16th to endDay
55%415%19%5%
2193
April1st to 15thDay
59%312%17%6%
2149
16th to endDay
61%312%15%6%
2432
May1st to 15thDay
53%211%18%12%
2511
16th to endDay
59%213%19%4
2697
June1st to 15thDay
57%311%17%9%1
2880
16th to endDay
53%314%20%7%
2880
July1st to 15thDay
38%313%25%16%2
2587
16th to endDay
34%316%32%11%1
2593
August1st to 15thDay
33%218%31%12%
2503
16th to endDay
39%218%27%10%1
2457
September1st to 15thDay
35%216%31%12%1
2160
16th to endDay
49%314%21%8%2
1928
October1st to 15thDay
46%220%24%5%
1650
16th to endDay
54%5%18%18%2
1616
November1st to 15thDay
59%5%13%15%5%
1408
16th to endDay
61%5%13%15%4
1367
December1st to 15thDay
65%5%12%13%2
1152
16th to endDay
62%5%13%13%3
1171
January1st to 15thNight
68%412%10%2
2686
16th to endNight
58%6%16%13%31
2772
February1st to 15thNight
60%313%16%5%
2369
16th to endNight
47%319%21%8%
2020
March1st to 15thNight
52%416%19%6%
2122
16th to endNight
50%418%21%4
2031
April1st to 15thNight
51%5%13%22%7%
1799
16th to endNight
55%411%20%7%
1527
May1st to 15thNight
53%310%20%10%1
1440
16th to endNight
57%316%17%5%
1412
June1st to 15thNight
58%310%20%6%1
1080
16th to endNight
52%315%18%8%
1080
July1st to 15thNight
38%5%12%24%16%3
1141
16th to endNight
38%215%28%12%
1313
August1st to 15thNight
31%315%33%12%2
1432
16th to endNight
35%219%28%10%2
1744
September1st to 15thNight
34%213%33%13%2
1800
16th to endNight
41%415%24%10%3
1888
October1st to 15thNight
46%317%25%6%
1980
16th to endNight
53%319%20%2
2254
November1st to 15thNight
55%5%16%16%5%
2450
16th to endNight
61%5%13%14%4
2580
December1st to 15thNight
62%5%14%15%2
2805
16th to endNight
64%6%13%13%2
3063

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
11%123%26%26%10%
60
16th to endDay
12%17%23%29%14%3
64
February1st to 15thDay
15%12%27%27%14%2
155
16th to endDay
15%12%23%25%16%5%
217
March1st to 15thDay
20%24%28%18%7%1
270
16th to endDay
18%22%34%20%21
288
April1st to 15thDay
17%19%28%21%8%4
269
16th to endDay
16%20%28%23%7%3
270
May1st to 15thDay
14%18%25%24%11%5%
288
16th to endDay
18%9%17%26%18%8%
408
June1st to 15thDay
21%8%22%22%20%3
675
16th to endDay
17%8%20%27%21%5%
675
July1st to 15thDay
11%6%26%31%18%5%
521
16th to endDay
11%6%20%33%21%7%
435
August1st to 15thDay
9%315%31%27%12%
315
16th to endDay
9%10%26%27%18%6%
332
September1st to 15thDay
14%11%24%24%17%8%
315
16th to endDay
17%13%22%25%13%6%
288
October1st to 15thDay
17%15%28%19%13%6%
255
16th to endDay
18%15%24%22%12%5%
137
November1st to 15thDay
26%23%28%11%10%
60
16th to endDay
18%6%15%26%21%11%
60
December1st to 15thDay
18%10%18%20%20%13%
60
16th to endDay
18%6%26%25%9%14%
64
January1st to 15thNight
22%9%19%32%13%3
750
16th to endNight
15%8%23%34%15%2
782
February1st to 15thNight
17%8%17%37%15%2
704
16th to endNight
12%8%18%39%19%2
632
March1st to 15thNight
14%15%25%30%10%2
720
16th to endNight
10%16%26%28%15%2
768
April1st to 15thNight
10%11%21%31%21%3
719
16th to endNight
14%10%25%31%14%2
447
May1st to 15thNight
15%8%24%32%19%
360
16th to endNight
20%7%14%29%24%3
375
June1st to 15thNight
19%6%18%32%20%2
360
16th to endNight
15%8%19%35%18%2
360
July1st to 15thNight
9%221%32%31%3
340
16th to endNight
10%5%15%33%29%5%
376
August1st to 15thNight
6%5%9%30%40%7%
360
16th to endNight
10%5%15%33%31%2
598
September1st to 15thNight
11%415%31%29%6%
720
16th to endNight
17%7%20%27%23%3
692
October1st to 15thNight
15%11%16%34%19%2
660
16th to endNight
19%11%21%29%15%2
704
November1st to 15thNight
21%16%21%28%11%1
700
16th to endNight
23%10%20%30%12%3
780
December1st to 15thNight
18%9%18%34%17%1
917
16th to endNight
15%12%21%37%11%1
983
Page generated at 2017-09-25 06:02:20. Version ac04

Copyright 2017 A. Danko


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