Woodland Hills
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodland Hills clear sky chart from 2005-11-05 to 2017-09-17.

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
76%
15824
33%
46829
29%
15778
80%
15778
51%
23165

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
66%
716
29%
2449
27%
716
73%
716
42%
1202
January16th to endNight
61%
768
35%
2397
30%
768
70%
768
42%
1245
February1st to 15thNight
71%
697
35%
2103
34%
697
77%
697
47%
1070
February16th to endNight
63%
632
28%
1895
28%
632
68%
632
36%
1082
March1st to 15thNight
68%
720
28%
2160
27%
720
75%
720
48%
1089
March16th to endNight
73%
768
28%
1992
22%
768
77%
768
47%
1115
April1st to 15thNight
67%
719
30%
1799
19%
719
71%
719
50%
1013
April16th to endNight
75%
720
31%
1800
16%
720
79%
720
58%
946
May1st to 15thNight
74%
644
27%
1724
19%
644
75%
644
47%
960
May16th to endNight
79%
561
28%
1685
22%
561
81%
561
52%
840
June1st to 15thNight
85%
421
28%
1501
30%
421
86%
421
48%
678
June16th to endNight
93%
360
36%
1440
44%
360
93%
360
60%
515
July1st to 15thNight
90%
340
33%
1360
41%
340
90%
340
54%
527
July16th to endNight
88%
621
30%
1641
25%
579
89%
579
56%
806
August1st to 15thNight
88%
717
34%
1790
22%
713
88%
713
64%
904
August16th to endNight
91%
764
42%
1910
28%
764
91%
764
72%
908
September1st to 15thNight
88%
720
38%
1812
30%
720
88%
720
65%
911
September16th to endNight
91%
664
41%
1837
41%
664
92%
664
70%
811
October1st to 15thNight
80%
660
35%
1854
35%
660
82%
660
54%
922
October16th to endNight
79%
704
40%
2115
42%
704
82%
704
55%
994
November1st to 15thNight
79%
700
35%
2275
36%
700
84%
700
56%
992
November16th to endNight
75%
720
37%
2340
37%
720
80%
720
50%
1085
December1st to 15thNight
68%
720
35%
2340
31%
720
75%
720
40%
1200
December16th to endNight
59%
768
32%
2610
29%
768
68%
768
36%
1350

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
4312213346%68%
47923
Night
4312212336%66%
47032
TransparencyDay
18%48%18%26%24%
47616
Night
20%37%16%25%26%
46839
SeeingDay
4420%35%28%6%
5958
Night
6%19%31%40%10%
15838

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
6%42332224462%
1486
16th to endDay
11%413212346%58%
1824
February1st to 15thDay
7%31321335%6%61%
1751
16th to endDay
10%413323345%55%
1579
March1st to 15thDay
5%2142135%37%61%
1800
16th to endDay
431242446%7%57%
2229
April1st to 15thDay
5%313323347%60%
2149
16th to endDay
4312112336%70%
2160
May1st to 15thDay
3412213347%64%
2226
16th to endDay
2322213345%68%
2429
June1st to 15thDay
45%12212337%65%
2454
16th to endDay
11211123380%
2520
July1st to 15thDay
1211213236%71%
2520
16th to endDay
1212212345%72%
2405
August1st to 15thDay
12111223477%
2160
16th to endDay
11212225%80%
2292
September1st to 15thDay
111111235%79%
2148
16th to endDay
1111312478%
1828
October1st to 15thDay
4311222245%69%
1773
16th to endDay
21232324371%
1755
November1st to 15thDay
3312223225%69%
1584
16th to endDay
4313312347%64%
1620
December1st to 15thDay
6%31232435%9%57%
1620
16th to endDay
9%323323336%57%
1611
January1st to 15thNight
7%313313347%60%
2449
16th to endNight
9%413312236%60%
2397
February1st to 15thNight
5%324212246%63%
2101
16th to endNight
12%323323345%54%
1895
March1st to 15thNight
442321235%8%61%
2160
16th to endNight
431232445%7%59%
1992
April1st to 15thNight
6%423212235%64%
1799
16th to endNight
3212213347%68%
1800
May1st to 15thNight
5%412222347%62%
1724
16th to endNight
2312212335%69%
1684
June1st to 15thNight
2321213349%65%
1501
16th to endNight
111212236%77%
1440
July1st to 15thNight
122322227%72%
1440
16th to endNight
2113212448%66%
1757
August1st to 15thNight
331212246%71%
1800
16th to endNight
21212246%75%
1910
September1st to 15thNight
22121123475%
1812
16th to endNight
11112335%78%
1837
October1st to 15thNight
32322333469%
1854
16th to endNight
3322233471%
2115
November1st to 15thNight
321221323473%
2275
16th to endNight
4212213446%66%
2340
December1st to 15thNight
7%324223346%60%
2340
16th to endNight
11%312222325%61%
2610

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
25%36%12%24%27%
1486
16th to endDay
27%47%16%16%27%
1824
February1st to 15thDay
22%37%15%25%25%
1751
16th to endDay
29%5%9%17%27%11%
1579
March1st to 15thDay
21%5%9%21%20%20%
1800
16th to endDay
23%5%13%23%18%15%
2229
April1st to 15thDay
21%5%12%24%22%12%
2149
16th to endDay
15%411%23%27%17%
2160
May1st to 15thDay
18%7%10%20%25%17%
2226
16th to endDay
17%412%27%28%9%
2432
June1st to 15thDay
20%5%9%17%30%16%
2454
16th to endDay
11%15%11%35%34%
2520
July1st to 15thDay
14%26%14%29%32%
2371
16th to endDay
14%48%22%30%20%
2258
August1st to 15thDay
12%15%15%34%30%
2146
16th to endDay
8%1414%40%30%
2292
September1st to 15thDay
10%26%15%30%34%
2148
16th to endDay
11%25%17%32%31%
1828
October1st to 15thDay
16%38%20%24%26%
1773
16th to endDay
16%45%15%22%36%
1755
November1st to 15thDay
19%25%14%23%33%
1584
16th to endDay
20%47%13%22%31%
1620
December1st to 15thDay
24%5%9%16%21%22%
1620
16th to endDay
28%48%16%21%20%
1611
January1st to 15thNight
24%46%14%22%28%
2449
16th to endNight
26%37%14%16%31%
2397
February1st to 15thNight
22%37%16%23%26%
2112
16th to endNight
32%38%16%24%15%
1895
March1st to 15thNight
21%310%18%23%20%
2160
16th to endNight
23%5%12%21%21%15%
1992
April1st to 15thNight
23%39%25%23%14%
1799
16th to endNight
16%312%22%24%19%
1800
May1st to 15thNight
22%6%9%19%25%16%
1725
16th to endNight
18%5%10%26%26%12%
1685
June1st to 15thNight
17%5%13%18%28%15%
1501
16th to endNight
12%27%13%32%31%
1440
July1st to 15thNight
16%15%13%26%36%
1360
16th to endNight
17%38%23%26%20%
1641
August1st to 15thNight
16%15%12%35%28%
1790
16th to endNight
12%15%13%37%30%
1910
September1st to 15thNight
14%25%10%30%35%
1812
16th to endNight
11%15%14%31%36%
1837
October1st to 15thNight
18%36%16%27%27%
1854
16th to endNight
17%25%13%22%38%
2115
November1st to 15thNight
15%37%14%22%37%
2275
16th to endNight
18%46%16%20%33%
2340
December1st to 15thNight
25%47%15%20%26%
2340
16th to endNight
26%47%14%24%21%
2610

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
14%7%34%35%7%
114
16th to endDay
11%9%33%31%13%1
272
February1st to 15thDay
8%6%29%35%17%1
266
16th to endDay
12%10%30%33%12%
238
March1st to 15thDay
5%10%28%28%23%2
270
16th to endDay
48%33%36%13%3
288
April1st to 15thDay
6%10%32%33%10%6%
269
16th to endDay
111%40%32%11%2
270
May1st to 15thDay
46%29%36%18%3
288
16th to endDay
3425%41%21%3
330
June1st to 15thDay
8%120%36%27%6%
315
16th to endDay
6%34%43%14%
315
July1st to 15thDay
2331%48%13%
305
16th to endDay
2326%51%15%
327
August1st to 15thDay
25%35%46%7%
315
16th to endDay
431%50%13%
332
September1st to 15thDay
310%45%34%6%
315
16th to endDay
112%49%28%7%
260
October1st to 15thDay
3325%45%20%3
255
16th to endDay
4419%42%25%2
267
November1st to 15thDay
5%410%30%35%14%
90
16th to endDay
36%23%40%24%2
90
December1st to 15thDay
37%15%31%40%2
90
16th to endDay
9%12%24%32%18%2
77
January1st to 15thNight
8%216%41%23%6%
720
16th to endNight
12%215%37%26%4
768
February1st to 15thNight
6%112%39%30%8%
704
16th to endNight
13%214%37%25%5%
632
March1st to 15thNight
6%215%38%30%6%
720
16th to endNight
5%112%38%35%5%
768
April1st to 15thNight
8%214%40%30%3
719
16th to endNight
3312%38%35%6%
720
May1st to 15thNight
8%110%36%37%6%
645
16th to endNight
312%36%40%6%
563
June1st to 15thNight
35%34%49%6%
421
16th to endNight
1121%66%9%
360
July1st to 15thNight
216%68%20%
340
16th to endNight
228%64%23%
621
August1st to 15thNight
313%62%18%
717
16th to endNight
211%58%26%
764
September1st to 15thNight
3318%52%21%
720
16th to endNight
1223%54%17%
664
October1st to 15thNight
5%16%33%42%10%
660
16th to endNight
5%18%29%40%13%
704
November1st to 15thNight
3210%35%35%12%
700
16th to endNight
6%111%35%34%11%
720
December1st to 15thNight
9%211%39%29%7%
720
16th to endNight
13%417%37%21%5%
768
Page generated at 2017-09-18 05:38:27. Version ac04

Copyright 2017 A. Danko


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