El Camino Real Historic Trail Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the El Camino Real Historic Trail Site 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
66%
15483
33%
47208
25%
15441
75%
15441
50%
23085

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
64%
717
34%
2327
30%
716
74%
716
52%
1074
January16th to endNight
60%
768
37%
2496
29%
768
73%
768
51%
1140
February1st to 15thNight
60%
700
35%
2219
26%
696
73%
696
57%
984
February16th to endNight
52%
632
39%
1878
24%
632
68%
632
51%
927
March1st to 15thNight
57%
720
38%
1980
24%
720
68%
720
58%
961
March16th to endNight
57%
760
37%
2104
21%
760
70%
760
59%
999
April1st to 15thNight
49%
539
36%
1798
19%
539
70%
539
53%
762
April16th to endNight
49%
540
40%
1800
25%
540
72%
540
56%
758
May1st to 15thNight
56%
539
30%
1799
24%
539
68%
539
53%
785
May16th to endNight
65%
562
33%
1702
25%
561
74%
561
56%
792
June1st to 15thNight
72%
540
28%
1620
24%
540
76%
540
55%
746
June16th to endNight
79%
540
22%
1620
21%
540
80%
540
48%
814
July1st to 15thNight
79%
510
20%
1530
19%
510
79%
510
32%
921
July16th to endNight
80%
564
18%
1593
17%
531
80%
531
30%
986
August1st to 15thNight
79%
539
18%
1704
18%
536
80%
536
31%
1019
August16th to endNight
79%
573
22%
1910
25%
573
80%
573
30%
1127
September1st to 15thNight
75%
540
24%
1800
26%
540
76%
540
31%
1045
September16th to endNight
78%
583
36%
1834
32%
583
83%
583
53%
867
October1st to 15thNight
73%
660
37%
1980
26%
660
80%
660
56%
937
October16th to endNight
76%
704
41%
2112
30%
704
83%
704
64%
920
November1st to 15thNight
73%
700
44%
2100
32%
700
82%
700
69%
879
November16th to endNight
65%
837
41%
2277
27%
837
73%
837
56%
1132
December1st to 15thNight
64%
900
35%
2481
23%
900
73%
900
52%
1273
December16th to endNight
62%
816
36%
2544
29%
816
71%
816
48%
1237

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
321232345%7%65%
47585
Night
3212323447%64%
47415
TransparencyDay
17%48%17%27%23%
47281
Night
19%48%16%27%23%
47220
SeeingDay
5%8%20%31%25%10%
5064
Night
4221%41%27%2
15492

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
2213323247%67%
1611
16th to endDay
412212236%70%
1728
February1st to 15thDay
211222135%75%
1632
16th to endDay
221213436%71%
1594
March1st to 15thDay
211222435%8%65%
1980
16th to endDay
1112212347%71%
2118
April1st to 15thDay
211123346%72%
2150
16th to endDay
111213235%75%
2160
May1st to 15thDay
112313446%70%
2151
16th to endDay
2112213345%71%
2408
June1st to 15thDay
111121345%8%68%
2340
16th to endDay
221231446%8%63%
2340
July1st to 15thDay
5%212425%7%8%11%47%
2340
16th to endDay
32145%46%7%9%14%41%
2467
August1st to 15thDay
4213435%7%7%11%48%
2246
16th to endDay
4313335%7%8%10%48%
2292
September1st to 15thDay
7%214425%5%7%9%50%
2160
16th to endDay
422212236%71%
1869
October1st to 15thDay
312212345%71%
1650
16th to endDay
11221223477%
1760
November1st to 15thDay
11111223477%
1759
16th to endDay
321221324472%
1668
December1st to 15thDay
322222247%69%
1476
16th to endDay
3314222247%65%
1686
January1st to 15thNight
3212213346%68%
2327
16th to endNight
4211222345%68%
2496
February1st to 15thNight
2312212335%72%
2219
16th to endNight
1213223337%67%
1878
March1st to 15thNight
221221235%6%69%
1980
16th to endNight
211221332474%
2104
April1st to 15thNight
221213447%68%
1798
16th to endNight
1112212335%74%
1800
May1st to 15thNight
222213346%69%
1799
16th to endNight
311121335%6%69%
1702
June1st to 15thNight
1213212348%67%
1620
16th to endNight
11133245%6%9%59%
1620
July1st to 15thNight
3225%5%46%7%7%10%43%
1620
16th to endNight
33147%47%7%7%14%38%
1701
August1st to 15thNight
33245%46%6%10%12%40%
1713
16th to endNight
33145%47%7%8%10%43%
1910
September1st to 15thNight
6%3235%36%5%7%9%46%
1800
16th to endNight
321232225%5%69%
1834
October1st to 15thNight
2112222345%70%
1980
16th to endNight
212112225%77%
2112
November1st to 15thNight
11111223478%
2100
16th to endNight
3212113225%71%
2277
December1st to 15thNight
4212323345%66%
2481
16th to endNight
5%31221335%6%64%
2544

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%46%19%36%14%
1612
16th to endDay
16%26%20%36%16%
1728
February1st to 15thDay
13%25%21%31%24%
1633
16th to endDay
15%3413%40%23%
1594
March1st to 15thDay
16%36%14%33%25%
1980
16th to endDay
14%2412%34%30%
2118
April1st to 15thDay
13%25%13%33%31%
2150
16th to endDay
12%2411%29%39%
2160
May1st to 15thDay
14%46%14%27%33%
2151
16th to endDay
14%36%11%24%38%
2411
June1st to 15thDay
12%47%13%19%42%
2340
16th to endDay
16%49%15%18%35%
2340
July1st to 15thDay
26%8%13%20%16%14%
2201
16th to endDay
27%11%20%26%10%2
2312
August1st to 15thDay
25%11%18%21%17%5%
2231
16th to endDay
26%9%15%23%16%8%
2292
September1st to 15thDay
28%7%14%19%18%11%
2160
16th to endDay
16%37%19%29%23%
1869
October1st to 15thDay
14%48%12%31%27%
1650
16th to endDay
11%2416%36%27%
1760
November1st to 15thDay
10%35%18%37%24%
1759
16th to endDay
16%2415%37%22%
1668
December1st to 15thDay
15%37%25%35%11%
1476
16th to endDay
20%310%27%30%7%
1686
January1st to 15thNight
18%37%19%39%12%
2327
16th to endNight
18%37%15%38%16%
2496
February1st to 15thNight
15%35%20%29%26%
2229
16th to endNight
18%4412%34%25%
1878
March1st to 15thNight
15%35%16%30%28%
1980
16th to endNight
15%2412%33%31%
2104
April1st to 15thNight
15%35%12%34%29%
1798
16th to endNight
14%249%31%38%
1800
May1st to 15thNight
16%36%12%25%35%
1800
16th to endNight
16%37%12%21%38%
1703
June1st to 15thNight
15%47%13%16%43%
1620
16th to endNight
18%7%12%12%16%33%
1620
July1st to 15thNight
30%10%12%17%15%13%
1530
16th to endNight
32%10%21%23%11%1
1593
August1st to 15thNight
29%11%19%22%12%5%
1704
16th to endNight
30%10%16%21%12%7%
1910
September1st to 15thNight
31%8%16%18%13%11%
1800
16th to endNight
17%37%17%27%25%
1834
October1st to 15thNight
15%47%14%26%31%
1980
16th to endNight
12%3317%28%34%
2112
November1st to 15thNight
10%2317%36%29%
2100
16th to endNight
17%3314%33%27%
2277
December1st to 15thNight
19%36%19%33%16%
2481
16th to endNight
19%49%24%34%7%
2544

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%424%45%12%2
90
16th to endDay
7%31%34%17%9%
96
February1st to 15thDay
7%216%28%37%6%
90
16th to endDay
5%11%25%36%13%7%
95
March1st to 15thDay
5%16%29%32%12%3
270
16th to endDay
322%35%26%10%2
288
April1st to 15thDay
5%22%30%29%9%2
269
16th to endDay
425%30%28%7%2
270
May1st to 15thDay
319%32%31%11%2
288
16th to endDay
110%38%30%16%2
330
June1st to 15thDay
3426%34%22%8%
315
16th to endDay
313%36%31%14%
315
July1st to 15thDay
5%5%30%43%14%
305
16th to endDay
6%5%23%37%27%
327
August1st to 15thDay
21426%45%20%
315
16th to endDay
6%6%27%38%20%
332
September1st to 15thDay
6%111%34%33%12%
315
16th to endDay
5%311%42%31%4
202
October1st to 15thDay
7%14%31%23%23%
90
16th to endDay
9%110%32%29%17%
96
November1st to 15thDay
7%5%22%21%33%10%
90
16th to endDay
5%14%25%32%22%
90
December1st to 15thDay
25%23%38%23%6%
90
16th to endDay
15%9%16%47%10%
96
January1st to 15thNight
5%122%43%23%3
720
16th to endNight
4428%40%20%1
768
February1st to 15thNight
3329%42%19%1
704
16th to endNight
35%37%46%8%
632
March1st to 15thNight
3431%44%15%
720
16th to endNight
25%30%45%15%
760
April1st to 15thNight
46%38%39%10%
539
16th to endNight
26%38%43%9%
540
May1st to 15thNight
3433%48%10%
540
16th to endNight
3225%52%15%
563
June1st to 15thNight
2218%54%22%
540
16th to endNight
311%48%35%
540
July1st to 15thNight
35%35%50%4
510
16th to endNight
4222%62%7%
564
August1st to 15thNight
5%321%58%11%
539
16th to endNight
4427%58%5%
573
September1st to 15thNight
6%16%33%48%4
540
16th to endNight
4112%42%37%2
583
October1st to 15thNight
3118%45%28%2
660
16th to endNight
2115%43%33%3
704
November1st to 15thNight
222%40%31%3
700
16th to endNight
4422%37%27%4
837
December1st to 15thNight
6%422%45%21%
900
16th to endNight
6%224%49%15%1
816
Page generated at 2017-09-20 02:49:48. Version ac04

Copyright 2017 A. Danko


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