Santa Barbara
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Santa Barbara 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
65%
15616
34%
46510
26%
15574
73%
15574
47%
22232

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
57%
716
29%
2395
23%
716
67%
716
33%
1208
January16th to endNight
55%
768
32%
2496
25%
768
67%
768
32%
1312
February1st to 15thNight
57%
700
35%
2104
32%
696
65%
696
38%
1086
February16th to endNight
52%
632
27%
1895
21%
632
62%
632
31%
1094
March1st to 15thNight
60%
720
27%
2106
22%
720
70%
720
40%
1071
March16th to endNight
59%
768
32%
2019
21%
768
67%
768
44%
1106
April1st to 15thNight
56%
719
31%
1799
18%
719
61%
719
44%
1000
April16th to endNight
60%
720
34%
1800
15%
720
67%
720
55%
905
May1st to 15thNight
63%
704
29%
1784
15%
704
68%
704
52%
908
May16th to endNight
61%
516
30%
1640
19%
516
69%
516
48%
726
June1st to 15thNight
65%
360
27%
1440
27%
360
72%
360
39%
603
June16th to endNight
77%
360
37%
1440
39%
360
85%
360
66%
430
July1st to 15thNight
81%
362
33%
1382
34%
362
84%
362
57%
484
July16th to endNight
73%
582
34%
1610
25%
548
82%
548
53%
739
August1st to 15thNight
82%
701
35%
1750
22%
697
83%
697
69%
807
August16th to endNight
85%
700
40%
1750
24%
700
89%
700
72%
795
September1st to 15thNight
81%
660
41%
1650
31%
660
83%
660
67%
779
September16th to endNight
81%
656
43%
1789
35%
656
89%
656
74%
739
October1st to 15thNight
74%
660
37%
1922
36%
660
78%
660
57%
878
October16th to endNight
72%
704
41%
2112
37%
704
82%
704
55%
943
November1st to 15thNight
66%
700
37%
2228
34%
700
75%
700
50%
979
November16th to endNight
63%
720
37%
2340
31%
720
75%
720
43%
1064
December1st to 15thNight
59%
720
34%
2371
29%
720
68%
720
35%
1205
December16th to endNight
52%
768
32%
2688
27%
768
64%
768
31%
1371

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
4212224346%65%
47442
Night
4212213346%67%
46710
TransparencyDay
17%411%19%27%19%
47130
Night
17%48%17%28%24%
46522
SeeingDay
411%14%31%31%5%
5882
Night
415%9%22%33%14%
15627

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
8%2332335%7%60%
1541
16th to endDay
12%312212236%60%
1728
February1st to 15thDay
9%313213246%60%
1746
16th to endDay
11%312325%346%54%
1579
March1st to 15thDay
5%1123246%5%7%59%
1853
16th to endDay
4223324348%59%
2204
April1st to 15thDay
5%113323347%61%
2149
16th to endDay
321211325%7%68%
2160
May1st to 15thDay
321222435%6%66%
2163
16th to endDay
212114347%69%
2471
June1st to 15thDay
2314225%246%61%
2520
16th to endDay
1116%245%74%
2520
July1st to 15thDay
2214236%347%60%
2492
16th to endDay
222335%446%62%
2448
August1st to 15thDay
1213335%448%61%
2114
16th to endDay
11224346%71%
2100
September1st to 15thDay
111223346%71%
1980
16th to endDay
1112224476%
1840
October1st to 15thDay
42222235%469%
1705
16th to endDay
113323335%71%
1760
November1st to 15thDay
22221335%471%
1628
16th to endDay
413213346%68%
1620
December1st to 15thDay
6%31332245%7%58%
1585
16th to endDay
10%312322336%60%
1536
January1st to 15thNight
7%213313346%61%
2395
16th to endNight
9%312323345%60%
2496
February1st to 15thNight
6%312323247%62%
2104
16th to endNight
12%41231234457%
1895
March1st to 15thNight
5%11222345%7%63%
2106
16th to endNight
421232335%7%63%
2019
April1st to 15thNight
6%312212246%65%
1799
16th to endNight
211113246%74%
1800
May1st to 15thNight
3212114247%69%
1784
16th to endNight
212216%245%69%
1639
June1st to 15thNight
214436%45%8%58%
1440
16th to endNight
114235%77%
1440
July1st to 15thNight
1212326%8%69%
1464
16th to endNight
1112326%45%6%64%
1719
August1st to 15thNight
112215%436%70%
1760
16th to endNight
1113325%78%
1750
September1st to 15thNight
22112323475%
1650
16th to endNight
1113235%79%
1789
October1st to 15thNight
312212245%73%
1922
16th to endNight
311211123475%
2112
November1st to 15thNight
221221222475%
2228
16th to endNight
3212212236%70%
2340
December1st to 15thNight
6%214313346%63%
2371
16th to endNight
9%312222246%62%
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
24%48%17%25%19%
1541
16th to endDay
27%48%15%21%21%
1728
February1st to 15thDay
25%5%6%18%26%17%
1746
16th to endDay
29%6%10%21%22%9%
1579
March1st to 15thDay
21%7%13%20%23%12%
1853
16th to endDay
24%6%12%24%22%10%
2204
April1st to 15thDay
22%7%11%24%24%9%
2149
16th to endDay
15%7%12%21%30%13%
2160
May1st to 15thDay
15%7%13%20%27%15%
2163
16th to endDay
12%6%15%27%28%10%
2474
June1st to 15thDay
18%416%19%27%14%
2520
16th to endDay
6%112%16%30%32%
2520
July1st to 15thDay
15%210%19%21%30%
2345
16th to endDay
16%412%22%26%17%
2294
August1st to 15thDay
13%113%20%29%22%
2100
16th to endDay
10%110%15%35%25%
2100
September1st to 15thDay
10%28%18%25%34%
1980
16th to endDay
8%110%15%36%28%
1840
October1st to 15thDay
17%410%17%28%22%
1705
16th to endDay
15%46%15%29%28%
1760
November1st to 15thDay
15%310%15%30%25%
1628
16th to endDay
18%49%15%28%23%
1620
December1st to 15thDay
24%7%9%17%24%16%
1585
16th to endDay
27%5%8%21%23%14%
1536
January1st to 15thNight
24%46%17%25%20%
2395
16th to endNight
26%47%12%22%25%
2496
February1st to 15thNight
22%5%6%18%27%19%
2115
16th to endNight
30%5%7%17%25%12%
1895
March1st to 15thNight
19%5%12%19%27%14%
2106
16th to endNight
20%6%10%23%24%13%
2019
April1st to 15thNight
21%5%9%24%27%10%
1799
16th to endNight
11%5%10%24%30%17%
1800
May1st to 15thNight
13%5%11%22%27%19%
1785
16th to endNight
13%412%20%33%15%
1640
June1st to 15thNight
17%5%12%18%29%17%
1440
16th to endNight
419%12%28%41%
1440
July1st to 15thNight
9%17%14%24%41%
1382
16th to endNight
13%47%23%24%26%
1610
August1st to 15thNight
9%17%16%27%37%
1750
16th to endNight
7%15%12%38%34%
1750
September1st to 15thNight
10%17%14%26%39%
1650
16th to endNight
5%16%11%39%34%
1789
October1st to 15thNight
13%37%16%30%27%
1922
16th to endNight
13%35%13%30%33%
2112
November1st to 15thNight
15%36%14%32%28%
2228
16th to endNight
17%36%19%26%25%
2340
December1st to 15thNight
23%5%8%16%24%21%
2371
16th to endNight
26%47%20%24%15%
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
15%15%21%32%12%2
169
16th to endDay
12%16%16%34%15%4
256
February1st to 15thDay
10%14%20%23%24%5%
265
16th to endDay
13%14%21%29%16%3
238
March1st to 15thDay
5%17%21%31%22%1
270
16th to endDay
418%21%32%20%2
288
April1st to 15thDay
5%18%21%31%20%2
269
16th to endDay
119%24%33%18%2
270
May1st to 15thDay
5%13%21%30%23%5%
288
16th to endDay
416%17%33%24%3
330
June1st to 15thDay
411%18%34%25%5%
315
16th to endDay
9%6%31%43%9%
315
July1st to 15thDay
26%6%31%42%9%
305
16th to endDay
39%6%22%46%12%
327
August1st to 15thDay
26%432%48%5%
300
16th to endDay
26%322%57%7%
268
September1st to 15thDay
5%5%5%34%43%5%
255
16th to endDay
7%7%31%47%5%
255
October1st to 15thDay
29%12%44%27%3
255
16th to endDay
27%17%34%33%3
272
November1st to 15thDay
28%10%23%41%14%
134
16th to endDay
35%18%46%22%3
90
December1st to 15thDay
4315%45%30%
84
16th to endDay
6%12%28%35%14%3
64
January1st to 15thNight
8%17%10%26%24%13%
720
16th to endNight
10%17%14%26%23%8%
768
February1st to 15thNight
7%18%12%27%25%10%
704
16th to endNight
12%17%13%26%23%7%
632
March1st to 15thNight
5%18%12%29%27%6%
720
16th to endNight
5%17%13%27%29%6%
768
April1st to 15thNight
5%19%14%28%24%6%
719
16th to endNight
219%15%28%25%9%
720
May1st to 15thNight
318%10%27%31%9%
705
16th to endNight
219%11%24%32%9%
518
June1st to 15thNight
16%10%24%37%10%
360
16th to endNight
16%217%45%16%
360
July1st to 15thNight
11%16%48%30%
362
16th to endNight
216%15%39%34%
582
August1st to 15thNight
19%210%48%26%
701
16th to endNight
9%18%45%34%
700
September1st to 15thNight
39%310%48%25%
660
16th to endNight
9%5%16%46%20%
656
October1st to 15thNight
39%8%21%44%12%
660
16th to endNight
39%10%25%35%14%
704
November1st to 15thNight
214%12%27%30%12%
700
16th to endNight
418%9%26%29%11%
720
December1st to 15thNight
5%19%10%29%27%8%
720
16th to endNight
9%20%13%29%20%5%
768
Page generated at 2017-08-13 11:16:32. Version ac04

Copyright 2017 A. Danko


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