Glenn Canyon's Wahweap district
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Glenn Canyon's Wahweap district clear sky chart from 2005-11-05 to 2017-09-22.

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
72%
15541
32%
46965
27%
15505
77%
15505
50%
23092

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
71%
716
26%
2327
25%
716
75%
716
39%
1247
January16th to endNight
70%
768
31%
2496
32%
768
74%
768
39%
1322
February1st to 15thNight
70%
700
26%
2262
28%
700
73%
700
41%
1175
February16th to endNight
61%
632
33%
1895
30%
632
70%
632
47%
983
March1st to 15thNight
67%
720
34%
1982
29%
720
73%
720
55%
995
March16th to endNight
66%
768
33%
2112
22%
768
74%
768
53%
1083
April1st to 15thNight
56%
665
27%
1924
15%
665
65%
665
48%
978
April16th to endNight
59%
540
39%
1653
25%
540
71%
540
55%
740
May1st to 15thNight
66%
539
32%
1619
24%
539
72%
539
54%
757
May16th to endNight
68%
561
31%
1685
23%
561
75%
561
58%
742
June1st to 15thNight
74%
540
29%
1620
25%
540
78%
540
63%
702
June16th to endNight
82%
540
34%
1620
33%
540
84%
540
75%
635
July1st to 15thNight
83%
510
22%
1530
20%
510
84%
510
48%
776
July16th to endNight
82%
564
23%
1593
21%
531
82%
531
35%
917
August1st to 15thNight
84%
539
28%
1611
25%
536
84%
536
47%
820
August16th to endNight
83%
573
37%
1776
34%
573
84%
573
48%
884
September1st to 15thNight
81%
711
31%
1971
27%
711
83%
711
52%
1018
September16th to endNight
81%
683
44%
1890
34%
683
87%
683
71%
832
October1st to 15thNight
74%
660
35%
1917
29%
660
78%
660
56%
919
October16th to endNight
75%
704
40%
2112
33%
704
81%
704
58%
972
November1st to 15thNight
80%
700
36%
2194
32%
700
84%
700
55%
991
November16th to endNight
75%
720
38%
2340
37%
720
81%
720
58%
1011
December1st to 15thNight
72%
720
28%
2340
27%
720
76%
720
45%
1160
December16th to endNight
63%
768
24%
2496
23%
768
68%
768
32%
1433

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
221332345%7%62%
47917
Night
221332335%7%63%
47160
TransparencyDay
20%5%9%20%25%19%
47612
Night
18%5%9%21%26%18%
46966
SeeingDay
47%17%31%28%10%
5370
Night
3215%41%32%4
15552

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
3426%7%6%6%45%7%45%
1611
16th to endDay
3326%5%35%5%5%10%50%
1728
February1st to 15thDay
24246%2346%13%49%
1599
16th to endDay
33244245%6%10%54%
1579
March1st to 15thDay
221232435%7%63%
1977
16th to endDay
2213312348%65%
2112
April1st to 15thDay
321232335%6%65%
2024
16th to endDay
1212222346%70%
2304
May1st to 15thDay
121222445%7%65%
2331
16th to endDay
211112335%7%69%
2429
June1st to 15thDay
11121223479%
2340
16th to endDay
1111123383%
2340
July1st to 15thDay
2213435%5%6%9%56%
2340
16th to endDay
33146%46%7%8%11%42%
2467
August1st to 15thDay
22145%35%5%7%9%51%
2340
16th to endDay
22123245%6%8%59%
2426
September1st to 15thDay
321342435%7%61%
1986
16th to endDay
211111235%76%
1882
October1st to 15thDay
311213346%70%
1711
16th to endDay
22131225%5%70%
1760
November1st to 15thDay
1112212346%73%
1663
16th to endDay
2213223346%67%
1620
December1st to 15thDay
45%244235%5%10%50%
1620
16th to endDay
6%5%27%7%47%5%5%9%38%
1728
January1st to 15thNight
3314434449%56%
2327
16th to endNight
4315%3335%5%8%55%
2496
February1st to 15thNight
231442335%8%59%
2251
16th to endNight
331342236%7%59%
1895
March1st to 15thNight
231222335%7%65%
1982
16th to endNight
211321336%8%63%
2112
April1st to 15thNight
3312324346%64%
1924
16th to endNight
212212337%70%
1653
May1st to 15thNight
221231335%7%66%
1619
16th to endNight
21111245%8%69%
1684
June1st to 15thNight
111112336%74%
1620
16th to endNight
1111226%81%
1620
July1st to 15thNight
1112325%5%6%11%57%
1620
16th to endNight
22135%46%8%8%10%45%
1701
August1st to 15thNight
12133345%7%8%58%
1620
16th to endNight
1224345%6%9%58%
1776
September1st to 15thNight
321331445%9%60%
1971
16th to endNight
221111235%79%
1890
October1st to 15thNight
221231225%5%69%
1917
16th to endNight
3212211226%72%
2112
November1st to 15thNight
1112214336%70%
2194
16th to endNight
3111212235%73%
2340
December1st to 15thNight
331232245%9%60%
2340
16th to endNight
4425%5%36%35%10%48%
2496

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
34%7%17%27%12%
1612
16th to endDay
26%7%15%30%19%
1728
February1st to 15thDay
25%6%15%27%20%4
1599
16th to endDay
23%5%10%24%29%6%
1579
March1st to 15thDay
18%37%28%33%8%
1977
16th to endDay
18%49%27%31%9%
2112
April1st to 15thDay
20%47%19%32%16%
2024
16th to endDay
15%45%20%33%21%
2304
May1st to 15thDay
17%47%15%35%18%
2331
16th to endDay
14%46%18%32%23%
2432
June1st to 15thDay
10%247%26%49%
2340
16th to endDay
8%115%17%65%
2340
July1st to 15thDay
23%6%11%12%13%32%
2201
16th to endDay
29%9%16%15%15%14%
2312
August1st to 15thDay
25%7%11%17%16%21%
2325
16th to endDay
20%5%10%15%24%23%
2426
September1st to 15thDay
21%6%9%14%19%29%
1986
16th to endDay
12%27%15%31%31%
1882
October1st to 15thDay
15%37%19%34%20%
1711
16th to endDay
14%48%22%38%10%
1760
November1st to 15thDay
12%410%33%31%9%
1663
16th to endDay
18%49%32%28%5%
1620
December1st to 15thDay
27%7%17%31%14%
1620
16th to endDay
37%10%16%22%10%1
1728
January1st to 15thNight
23%8%15%31%20%
2327
16th to endNight
25%6%12%29%22%2
2496
February1st to 15thNight
23%7%12%27%22%7%
2262
16th to endNight
21%5%8%27%29%7%
1895
March1st to 15thNight
18%38%23%37%9%
1982
16th to endNight
17%5%8%24%31%12%
2112
April1st to 15thNight
21%47%14%32%20%
1924
16th to endNight
14%3418%38%19%
1653
May1st to 15thNight
16%48%13%36%22%
1620
16th to endNight
12%48%18%30%25%
1685
June1st to 15thNight
12%247%21%51%
1620
16th to endNight
8%125%16%66%
1620
July1st to 15thNight
20%5%12%15%12%33%
1530
16th to endNight
28%8%13%17%14%17%
1593
August1st to 15thNight
18%7%12%17%19%23%
1611
16th to endNight
20%5%9%17%22%25%
1776
September1st to 15thNight
20%48%16%17%32%
1971
16th to endNight
10%15%16%26%39%
1890
October1st to 15thNight
16%36%15%32%25%
1917
16th to endNight
15%35%14%41%19%
2112
November1st to 15thNight
15%37%25%33%12%
2194
16th to endNight
14%37%26%38%10%
2340
December1st to 15thNight
20%7%15%33%23%1
2340
16th to endNight
30%8%18%28%11%2
2496

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
16%413%41%17%6%
90
16th to endDay
7%211%37%31%10%
96
February1st to 15thDay
6%5%8%33%33%13%
114
16th to endDay
5%10%28%28%21%5%
238
March1st to 15thDay
48%21%34%22%8%
270
16th to endDay
6%14%20%30%25%3
288
April1st to 15thDay
7%16%26%24%15%9%
269
16th to endDay
422%26%25%18%2
270
May1st to 15thDay
213%29%32%17%4
288
16th to endDay
411%22%29%23%9%
330
June1st to 15thDay
17%23%35%21%10%
315
16th to endDay
2116%28%34%16%
315
July1st to 15thDay
1112%37%33%13%
305
16th to endDay
218%32%35%19%
327
August1st to 15thDay
48%35%33%16%
315
16th to endDay
5%110%27%40%16%
332
September1st to 15thDay
2214%32%34%12%
315
16th to endDay
5%5%12%24%36%16%
280
October1st to 15thDay
35%16%32%27%13%
151
16th to endDay
8%18%31%37%4
96
November1st to 15thDay
211%31%35%20%
90
16th to endDay
47%18%40%26%2
90
December1st to 15thDay
418%48%33%3
90
16th to endDay
11%5%20%27%26%9%
96
January1st to 15thNight
4214%42%28%7%
720
16th to endNight
5%114%46%27%4
768
February1st to 15thNight
5%116%43%29%3
704
16th to endNight
5%226%46%17%1
632
March1st to 15thNight
3419%43%26%1
720
16th to endNight
2422%44%23%1
768
April1st to 15thNight
45%29%38%19%1
665
16th to endNight
26%27%38%21%2
540
May1st to 15thNight
3420%47%22%2
540
16th to endNight
25%21%41%26%2
563
June1st to 15thNight
2217%50%25%2
540
16th to endNight
12%44%40%1
540
July1st to 15thNight
26%41%46%3
510
16th to endNight
3433%53%4
564
August1st to 15thNight
215%34%51%4
539
16th to endNight
216%33%50%6%
573
September1st to 15thNight
46%35%48%5%
711
16th to endNight
3110%32%44%7%
683
October1st to 15thNight
3116%42%32%4
660
16th to endNight
4113%36%36%7%
704
November1st to 15thNight
2112%43%35%5%
700
16th to endNight
3116%40%32%5%
720
December1st to 15thNight
5%214%48%24%4
720
16th to endNight
6%317%42%25%3
768
Page generated at 2017-09-23 03:43:37. Version ac04

Copyright 2017 A. Danko


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