Wilkerson Pass
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wilkerson Pass clear sky chart from 2005-11-05 to 2017-09-19.

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
50%
15912
27%
46893
16%
15867
61%
15867
42%
24840

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
42%
900
31%
2506
15%
895
57%
895
50%
1216
January16th to endNight
44%
768
35%
2496
22%
768
62%
768
47%
1157
February1st to 15thNight
37%
700
27%
2253
12%
697
55%
697
42%
1122
February16th to endNight
36%
632
35%
1894
14%
632
57%
632
47%
931
March1st to 15thNight
42%
720
29%
2091
13%
720
56%
720
46%
1082
March16th to endNight
41%
693
28%
2037
13%
693
55%
693
39%
1104
April1st to 15thNight
38%
539
25%
1798
14%
539
54%
539
37%
912
April16th to endNight
37%
540
22%
1800
13%
540
52%
540
28%
1047
May1st to 15thNight
44%
540
20%
1639
14%
540
52%
540
29%
993
May16th to endNight
51%
562
17%
1498
10%
561
58%
561
36%
900
June1st to 15thNight
64%
540
23%
1440
15%
540
69%
540
51%
749
June16th to endNight
73%
540
25%
1440
20%
540
76%
540
52%
750
July1st to 15thNight
70%
510
16%
1360
15%
510
71%
510
33%
861
July16th to endNight
72%
564
16%
1487
15%
531
74%
531
32%
898
August1st to 15thNight
71%
539
16%
1665
16%
536
72%
536
31%
989
August16th to endNight
72%
573
23%
1910
26%
573
74%
573
33%
1080
September1st to 15thNight
65%
540
24%
1800
23%
540
72%
540
33%
1003
September16th to endNight
61%
510
32%
1804
27%
510
72%
510
43%
859
October1st to 15thNight
55%
660
32%
1980
18%
660
65%
660
45%
1010
October16th to endNight
57%
707
35%
2115
19%
707
68%
707
48%
1054
November1st to 15thNight
50%
875
35%
2275
17%
875
60%
875
54%
1170
November16th to endNight
48%
900
36%
2397
17%
900
60%
900
53%
1189
December1st to 15thNight
37%
900
25%
2520
11%
900
49%
900
46%
1275
December16th to endNight
35%
960
28%
2688
11%
960
49%
960
38%
1489

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
4425%4345%6%8%50%
47932
Night
342432345%8%58%
47072
TransparencyDay
29%5%12%25%20%6%
47613
Night
23%5%14%29%21%5%
46893
SeeingDay
10%12%26%28%17%4
5816
Night
48%29%39%15%1
15917

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
423324448%63%
1441
16th to endDay
42431335%7%62%
1728
February1st to 15thDay
426%33345%9%56%
1609
16th to endDay
42442345%8%60%
1580
March1st to 15thDay
15%2443446%8%55%
1866
16th to endDay
26%34425%45%8%51%
2187
April1st to 15thDay
36%34425%5%6%9%49%
2150
16th to endDay
411%36%5%45%5%5%6%42%
2160
May1st to 15thDay
7%8%36%6%345%6%8%38%
2307
16th to endDay
6%6%25%6%35%6%7%8%41%
2616
June1st to 15thDay
4424435%6%7%9%48%
2520
16th to endDay
42135%36%6%7%7%53%
2520
July1st to 15thDay
8%425%6%47%7%7%9%36%
2520
16th to endDay
9%5%36%6%37%6%6%9%35%
2577
August1st to 15thDay
9%5%26%7%46%6%5%8%36%
2286
16th to endDay
7%415%6%36%5%6%8%44%
2292
September1st to 15thDay
8%326%5%35%5%5%6%47%
2160
16th to endDay
4323424346%60%
1898
October1st to 15thDay
4314423448%57%
1650
16th to endDay
3314423346%62%
1746
November1st to 15thDay
131331235%7%66%
1583
16th to endDay
31431325%8%65%
1560
December1st to 15thDay
425%423348%59%
1440
16th to endDay
122442347%9%57%
1536
January1st to 15thNight
2322335%8%67%
2506
16th to endNight
1313312346%68%
2496
February1st to 15thNight
425%323248%61%
2243
16th to endNight
424313448%63%
1894
March1st to 15thNight
142432345%9%59%
2091
16th to endNight
35%24323348%59%
2037
April1st to 15thNight
16%23423347%59%
1798
16th to endNight
5%7%35%433446%50%
1800
May1st to 15thNight
6%8%45%43345%8%45%
1638
16th to endNight
6%5%2332447%9%49%
1497
June1st to 15thNight
221231335%10%62%
1440
16th to endNight
2223245%7%8%60%
1440
July1st to 15thNight
4425%5%35%7%8%10%41%
1440
16th to endNight
6%3246%36%7%6%12%40%
1589
August1st to 15thNight
6%415%5%25%5%7%9%47%
1674
16th to endNight
6%423435%5%6%9%47%
1910
September1st to 15thNight
7%4144235%6%9%48%
1800
16th to endNight
4322323446%62%
1804
October1st to 15thNight
4212223346%65%
1980
16th to endNight
241332346%6%62%
2115
November1st to 15thNight
212223347%67%
2275
16th to endNight
1313212348%67%
2397
December1st to 15thNight
131331345%9%61%
2520
16th to endNight
43442335%8%58%
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
19%420%32%18%4
1442
16th to endDay
20%314%34%20%5%
1728
February1st to 15thDay
23%418%32%16%3
1610
16th to endDay
22%412%30%25%4
1580
March1st to 15thDay
25%411%29%23%4
1866
16th to endDay
29%5%11%30%18%4
2187
April1st to 15thDay
30%5%12%28%16%6%
2150
16th to endDay
40%5%9%23%17%3
2160
May1st to 15thDay
41%6%13%20%17%
2307
16th to endDay
36%6%14%23%14%5%
2620
June1st to 15thDay
29%6%12%18%21%11%
2520
16th to endDay
25%6%8%22%26%11%
2520
July1st to 15thDay
38%8%12%17%15%8%
2371
16th to endDay
41%8%17%19%10%3
2416
August1st to 15thDay
42%7%14%14%13%6%
2271
16th to endDay
35%6%11%25%18%3
2292
September1st to 15thDay
33%5%10%20%20%8%
2160
16th to endDay
24%38%25%31%6%
1898
October1st to 15thDay
24%47%27%29%6%
1650
16th to endDay
22%37%27%31%6%
1746
November1st to 15thDay
17%410%28%26%11%
1583
16th to endDay
17%28%32%29%8%
1560
December1st to 15thDay
22%417%32%18%3
1440
16th to endDay
21%6%18%29%18%5%
1536
January1st to 15thNight
16%319%34%22%3
2506
16th to endNight
18%312%33%25%6%
2496
February1st to 15thNight
22%314%39%15%3
2253
16th to endNight
20%210%34%25%5%
1894
March1st to 15thNight
20%411%34%24%3
2091
16th to endNight
25%411%33%21%3
2037
April1st to 15thNight
24%412%32%20%5%
1798
16th to endNight
35%412%27%16%3
1800
May1st to 15thNight
36%414%26%15%2
1639
16th to endNight
29%6%19%24%14%5%
1498
June1st to 15thNight
18%5%18%24%18%14%
1440
16th to endNight
18%6%13%25%22%13%
1440
July1st to 15thNight
33%8%16%19%14%6%
1360
16th to endNight
31%9%25%21%9%2
1487
August1st to 15thNight
31%8%19%20%14%5%
1665
16th to endNight
30%6%16%27%15%3
1910
September1st to 15thNight
29%7%16%21%17%8%
1800
16th to endNight
22%412%31%25%4
1804
October1st to 15thNight
19%6%10%27%29%7%
1980
16th to endNight
19%5%9%29%30%5%
2115
November1st to 15thNight
16%411%29%27%11%
2275
16th to endNight
16%310%33%27%8%
2397
December1st to 15thNight
18%421%32%19%3
2520
16th to endNight
24%6%17%29%19%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
6%17%18%30%26%
90
16th to endDay
2430%45%16%1
96
February1st to 15thDay
326%31%34%4
90
16th to endDay
29%30%22%14%2
81
March1st to 15thDay
5%22%35%26%8%
156
16th to endDay
10%29%37%17%4
288
April1st to 15thDay
11%29%31%18%6%1
269
16th to endDay
22%28%31%14%21
270
May1st to 15thDay
12%16%30%29%8%2
387
16th to endDay
10%14%26%27%18%3
517
June1st to 15thDay
8%10%25%29%21%5%
495
16th to endDay
5%5%25%31%25%6%
495
July1st to 15thDay
13%114%31%29%8%
475
16th to endDay
14%213%30%28%9%
436
August1st to 15thDay
17%423%33%14%7%
315
16th to endDay
15%324%32%17%6%
332
September1st to 15thDay
13%10%29%27%14%4
315
16th to endDay
38%35%26%19%7%
157
October1st to 15thDay
48%22%27%24%12%
90
16th to endDay
9%11%27%29%16%6%
96
November1st to 15thDay
37%23%24%30%11%
90
16th to endDay
218%45%25%7%
90
December1st to 15thDay
422%42%27%3
90
16th to endDay
114%40%37%33
96
January1st to 15thNight
113%36%36%9%1
900
16th to endNight
29%37%41%8%
768
February1st to 15thNight
28%45%38%5%
704
16th to endNight
210%44%36%5%
632
March1st to 15thNight
28%40%39%8%
720
16th to endNight
5%11%36%39%5%
693
April1st to 15thNight
5%14%35%38%5%
539
16th to endNight
10%13%34%33%8%
540
May1st to 15thNight
11%7%29%39%12%
540
16th to endNight
9%7%24%39%17%2
563
June1st to 15thNight
4421%48%18%2
540
16th to endNight
3117%49%27%1
540
July1st to 15thNight
8%16%38%40%5%
510
16th to endNight
7%2434%45%5%
564
August1st to 15thNight
9%16%41%37%3
539
16th to endNight
9%16%42%38%2
573
September1st to 15thNight
8%113%40%29%5%
540
16th to endNight
5%321%43%22%3
510
October1st to 15thNight
5%6%28%40%16%2
660
16th to endNight
45%28%42%16%2
707
November1st to 15thNight
29%33%40%12%1
875
16th to endNight
310%33%43%8%1
900
December1st to 15thNight
213%41%36%6%
900
16th to endNight
214%40%35%7%
960
Page generated at 2017-09-20 02:49:47. Version ac04

Copyright 2017 A. Danko


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