Great Sand Dunes National Park and Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Sand Dunes National Park and Preserve clear sky chart from 2005-11-05 to 2017-08-12.

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%
15734
26%
46514
13%
15689
53%
15689
34%
25794

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
36%
861
27%
2467
14%
856
50%
856
43%
1271
January16th to endNight
36%
768
31%
2496
18%
768
52%
768
39%
1239
February1st to 15thNight
26%
702
23%
2229
10%
700
41%
700
33%
1202
February16th to endNight
19%
632
32%
1894
9%
632
43%
632
35%
1007
March1st to 15thNight
31%
720
26%
2085
9%
720
45%
720
35%
1144
March16th to endNight
30%
695
28%
2039
11%
695
46%
695
34%
1114
April1st to 15thNight
25%
539
23%
1798
8%
539
43%
539
25%
982
April16th to endNight
29%
540
24%
1800
10%
540
47%
540
24%
994
May1st to 15thNight
31%
540
19%
1711
9%
540
45%
540
25%
1015
May16th to endNight
35%
563
21%
1497
8%
561
47%
561
29%
890
June1st to 15thNight
45%
540
25%
1440
13%
540
55%
540
42%
778
June16th to endNight
59%
540
23%
1440
15%
540
65%
540
41%
802
July1st to 15thNight
59%
510
14%
1360
10%
510
61%
510
26%
924
July16th to endNight
72%
564
13%
1528
13%
531
73%
531
23%
1052
August1st to 15thNight
65%
527
13%
1652
12%
524
66%
524
23%
1079
August16th to endNight
67%
525
17%
1750
18%
525
70%
525
27%
1079
September1st to 15thNight
55%
495
23%
1650
18%
495
64%
495
27%
1017
September16th to endNight
57%
492
34%
1763
26%
492
69%
492
42%
813
October1st to 15thNight
44%
660
32%
1980
17%
660
57%
660
39%
1046
October16th to endNight
45%
704
36%
2112
17%
704
60%
704
44%
1047
November1st to 15thNight
41%
857
35%
2257
14%
857
54%
857
50%
1132
November16th to endNight
39%
900
35%
2358
15%
900
53%
900
47%
1238
December1st to 15thNight
27%
900
23%
2520
7%
900
42%
900
38%
1388
December16th to endNight
27%
960
25%
2688
10%
960
40%
960
32%
1541

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
3424435%5%6%8%51%
47464
Night
24244245%5%7%56%
46698
TransparencyDay
28%7%14%24%19%5%
47149
Night
25%7%14%26%21%5%
46515
SeeingDay
11%20%31%23%10%1
5593
Night
6%15%33%28%14%2
15736

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
325%42345%8%59%
1480
16th to endDay
42431235%7%61%
1728
February1st to 15thDay
1336%42435%8%55%
1631
16th to endDay
5%344245%5%8%55%
1580
March1st to 15thDay
15%46%42445%9%52%
1872
16th to endDay
26%26%435%45%7%51%
2184
April1st to 15thDay
26%35%5%35%45%9%49%
2150
16th to endDay
48%346%346%5%8%44%
2160
May1st to 15thDay
5%6%36%5%36%5%6%7%41%
2238
16th to endDay
4425%5%25%5%6%7%51%
2616
June1st to 15thDay
3313425%5%7%9%52%
2520
16th to endDay
1212425%5%7%9%56%
2520
July1st to 15thDay
5%325%6%48%7%8%9%38%
2520
16th to endDay
4435%6%48%8%10%10%33%
2532
August1st to 15thDay
6%426%6%47%7%9%8%36%
2212
16th to endDay
5%5%15%5%37%6%8%10%40%
2100
September1st to 15thDay
5%425%5%36%6%6%8%45%
1980
16th to endDay
2213424445%63%
1864
October1st to 15thDay
35%23424446%59%
1650
16th to endDay
2313413336%65%
1760
November1st to 15thDay
323223249%64%
1589
16th to endDay
1323223347%63%
1602
December1st to 15thDay
5%2441436%8%58%
1440
16th to endDay
1435%42446%11%51%
1536
January1st to 15thNight
313423446%65%
2467
16th to endNight
323423447%62%
2496
February1st to 15thNight
15%36%313346%58%
2219
16th to endNight
425%42335%8%58%
1894
March1st to 15thNight
15%2441345%9%57%
2085
16th to endNight
26%24413347%59%
2039
April1st to 15thNight
15%2443445%7%55%
1798
16th to endNight
27%24335%5%5%8%50%
1800
May1st to 15thNight
46%25%5%36%6%46%48%
1710
16th to endNight
44134346%6%9%51%
1497
June1st to 15thNight
23325%5%5%8%60%
1440
16th to endNight
1212326%7%8%7%55%
1440
July1st to 15thNight
4446%7%36%6%7%9%37%
1440
16th to endNight
43246%5%9%8%9%8%36%
1634
August1st to 15thNight
4427%7%46%6%7%8%41%
1661
16th to endNight
5%3245%37%9%8%9%40%
1750
September1st to 15thNight
5%415%5%36%6%7%8%44%
1650
16th to endNight
121332345%7%63%
1763
October1st to 15thNight
3313323447%62%
1980
16th to endNight
2313213346%65%
2112
November1st to 15thNight
1111223347%68%
2257
16th to endNight
2313323237%66%
2358
December1st to 15thNight
132442335%8%60%
2520
16th to endNight
1414435%45%8%56%
2688

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
22%5%21%29%18%2
1481
16th to endDay
21%5%16%33%17%4
1728
February1st to 15thDay
26%6%18%31%12%4
1632
16th to endDay
24%6%13%28%22%4
1580
March1st to 15thDay
28%414%24%23%4
1872
16th to endDay
30%5%11%29%19%2
2184
April1st to 15thDay
32%6%12%26%18%4
2150
16th to endDay
34%8%12%21%19%3
2160
May1st to 15thDay
38%7%13%21%16%2
2238
16th to endDay
29%8%13%21%19%6%
2620
June1st to 15thDay
25%7%14%17%21%13%
2520
16th to endDay
19%7%11%23%24%13%
2520
July1st to 15thDay
36%10%14%17%13%6%
2371
16th to endDay
36%15%20%19%6%
2375
August1st to 15thDay
38%12%15%15%12%5%
2197
16th to endDay
34%10%14%23%14%2
2100
September1st to 15thDay
32%10%12%20%17%6%
1980
16th to endDay
21%6%10%23%33%4
1864
October1st to 15thDay
25%49%27%27%4
1650
16th to endDay
20%410%29%31%4
1760
November1st to 15thDay
19%413%23%30%7%
1589
16th to endDay
19%411%31%26%6%
1602
December1st to 15thDay
22%6%23%29%16%1
1440
16th to endDay
26%10%21%25%14%2
1536
January1st to 15thNight
20%5%19%29%22%2
2467
16th to endNight
20%6%13%34%20%4
2496
February1st to 15thNight
27%5%18%29%16%2
2229
16th to endNight
24%5%12%29%23%3
1894
March1st to 15thNight
23%6%14%28%24%2
2085
16th to endNight
25%5%11%30%25%2
2039
April1st to 15thNight
27%7%12%26%20%4
1798
16th to endNight
30%6%14%27%19%2
1800
May1st to 15thNight
32%7%13%24%16%4
1711
16th to endNight
27%8%16%22%16%8%
1498
June1st to 15thNight
20%7%14%20%20%17%
1440
16th to endNight
20%9%13%20%21%13%
1440
July1st to 15thNight
38%10%15%15%10%8%
1360
16th to endNight
36%16%19%20%7%1
1528
August1st to 15thNight
36%13%18%15%11%5%
1652
16th to endNight
32%11%19%19%12%4
1750
September1st to 15thNight
33%10%15%20%13%6%
1650
16th to endNight
18%6%11%26%31%5%
1763
October1st to 15thNight
21%6%11%25%28%6%
1980
16th to endNight
19%47%28%33%5%
2112
November1st to 15thNight
15%412%29%31%6%
2257
16th to endNight
20%39%30%29%7%
2358
December1st to 15thNight
22%6%21%27%18%2
2520
16th to endNight
24%8%19%26%16%3
2688

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%28%32%17%10%
90
16th to endDay
7%27%33%23%8%
96
February1st to 15thDay
10%36%33%18%1
90
16th to endDay
11%34%30%18%4
81
March1st to 15thDay
15%29%32%19%3
162
16th to endDay
23%32%33%7%2
288
April1st to 15thDay
18%37%27%12%2
269
16th to endDay
22%44%24%7%1
270
May1st to 15thDay
12%29%35%17%31
357
16th to endDay
9%24%32%21%11%1
517
June1st to 15thDay
8%17%29%25%17%2
495
16th to endDay
5%9%31%29%21%3
495
July1st to 15thDay
10%6%27%32%18%4
475
16th to endDay
9%326%38%17%3
391
August1st to 15thDay
13%7%32%33%12%1
300
16th to endDay
10%8%38%34%8%
268
September1st to 15thDay
11%19%40%22%6%
255
16th to endDay
6%11%40%27%11%2
142
October1st to 15thDay
421%32%28%8%4
90
16th to endDay
9%28%26%25%9%2
96
November1st to 15thDay
6%15%28%28%17%2
90
16th to endDay
14%42%26%13%21
90
December1st to 15thDay
13%37%38%8%1
90
16th to endDay
12%40%35%10%1
96
January1st to 15thNight
415%40%26%10%2
861
16th to endNight
416%40%28%8%1
768
February1st to 15thNight
416%49%24%5%
704
16th to endNight
6%20%50%18%4
632
March1st to 15thNight
6%20%37%27%7%
720
16th to endNight
9%19%39%23%8%
695
April1st to 15thNight
10%23%36%24%4
539
16th to endNight
8%25%35%23%6%
540
May1st to 15thNight
7%19%36%25%9%1
540
16th to endNight
8%19%32%24%13%1
563
June1st to 15thNight
312%32%32%16%2
540
16th to endNight
28%24%37%24%2
540
July1st to 15thNight
8%316%32%32%5%
510
16th to endNight
5%29%32%43%7%
564
August1st to 15thNight
7%311%37%33%6%
527
16th to endNight
7%115%39%31%4
525
September1st to 15thNight
7%6%22%37%20%5%
495
16th to endNight
39%25%36%21%3
492
October1st to 15thNight
6%14%29%31%13%3
660
16th to endNight
414%32%29%16%2
704
November1st to 15thNight
5%15%34%29%13%
857
16th to endNight
7%16%35%27%10%1
900
December1st to 15thNight
6%21%42%23%5%
900
16th to endNight
5%24%38%23%7%
960
Page generated at 2017-08-13 12:16:42. Version ac04

Copyright 2017 A. Danko


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