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 2018-02-22.

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
66%
16396
34%
48871
27%
16354
74%
16354
47%
23340

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%
776
29%
2596
23%
776
67%
776
32%
1341
January16th to endNight
57%
832
33%
2704
26%
832
68%
832
33%
1407
February1st to 15thNight
60%
760
36%
2284
34%
756
67%
756
41%
1153
February16th to endNight
52%
660
29%
1979
23%
660
64%
660
32%
1124
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
81%
717
35%
1790
22%
713
83%
713
68%
830
August16th to endNight
85%
764
41%
1910
25%
764
88%
764
71%
877
September1st to 15thNight
81%
720
40%
1800
30%
720
83%
720
67%
858
September16th to endNight
81%
716
45%
1952
37%
716
89%
716
74%
809
October1st to 15thNight
76%
720
36%
2097
36%
720
80%
720
59%
942
October16th to endNight
72%
768
43%
2304
39%
768
83%
768
55%
1026
November1st to 15thNight
66%
760
35%
2419
32%
760
74%
760
47%
1097
November16th to endNight
64%
780
37%
2535
32%
780
75%
780
44%
1157
December1st to 15thNight
61%
780
34%
2569
30%
780
70%
780
37%
1279
December16th to endNight
54%
832
33%
2912
28%
832
66%
832
32%
1468

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%
49361
Night
4212213346%67%
49071
TransparencyDay
17%411%19%27%20%
49049
Night
17%48%17%28%24%
48883
SeeingDay
410%14%32%31%5%
6546
Night
414%9%23%33%14%
16407

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
9%2332325%7%58%
1670
16th to endDay
11%312212236%61%
1872
February1st to 15thDay
8%313213246%61%
1896
16th to endDay
11%312314346%56%
1641
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%45%8%61%
2160
16th to endDay
112224346%70%
2292
September1st to 15thDay
211222346%70%
2160
16th to endDay
11112224476%
2007
October1st to 15thDay
41221234471%
1860
16th to endDay
113323335%71%
1920
November1st to 15thDay
22221335%5%69%
1767
16th to endDay
311321335%7%67%
1755
December1st to 15thDay
6%31232245%7%60%
1717
16th to endDay
9%312222337%60%
1664
January1st to 15thNight
8%213323346%59%
2596
16th to endNight
8%312313346%60%
2704
February1st to 15thNight
6%312213237%64%
2284
16th to endNight
12%41231233459%
1979
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%
1800
16th to endNight
11113325%77%
1910
September1st to 15thNight
22112323475%
1800
16th to endNight
1113235%79%
1952
October1st to 15thNight
312212245%74%
2097
16th to endNight
321211123475%
2304
November1st to 15thNight
2212212335%72%
2419
16th to endNight
3212212236%69%
2535
December1st to 15thNight
5%113313346%64%
2569
16th to endNight
9%212213345%62%
2912

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
26%48%17%24%17%
1670
16th to endDay
27%48%16%22%20%
1872
February1st to 15thDay
24%47%17%27%19%
1896
16th to endDay
28%6%9%20%23%11%
1641
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%28%22%
2146
16th to endDay
10%110%15%35%25%
2292
September1st to 15thDay
11%28%18%26%32%
2160
16th to endDay
8%110%15%37%27%
2007
October1st to 15thDay
15%39%16%28%25%
1860
16th to endDay
15%36%15%28%30%
1920
November1st to 15thDay
16%310%17%29%23%
1767
16th to endDay
17%49%15%30%22%
1755
December1st to 15thDay
23%6%8%16%24%20%
1717
16th to endDay
25%5%7%20%25%14%
1664
January1st to 15thNight
26%47%18%24%19%
2596
16th to endNight
25%5%7%13%23%24%
2704
February1st to 15thNight
20%47%17%28%20%
2295
16th to endNight
29%5%7%17%26%13%
1979
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
10%17%17%26%37%
1790
16th to endNight
8%16%12%38%33%
1910
September1st to 15thNight
11%18%13%28%37%
1800
16th to endNight
6%17%11%40%33%
1952
October1st to 15thNight
13%37%15%30%30%
2097
16th to endNight
13%35%14%28%35%
2304
November1st to 15thNight
17%36%15%30%25%
2419
16th to endNight
17%37%18%27%25%
2535
December1st to 15thNight
22%5%8%15%24%24%
2569
16th to endNight
25%48%19%25%16%
2912

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%12%20%31%17%2
208
16th to endDay
11%14%16%33%19%5%
304
February1st to 15thDay
8%12%18%23%28%8%
325
16th to endDay
12%13%22%28%18%4
264
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
35%5%31%47%5%
315
16th to endDay
25%424%55%8%
332
September1st to 15thDay
5%47%36%41%4
315
16th to endDay
26%6%33%45%5%
315
October1st to 15thDay
27%10%46%28%3
315
16th to endDay
36%16%32%33%7%
336
November1st to 15thDay
36%9%33%37%10%
183
16th to endDay
35%15%40%27%7%
135
December1st to 15thDay
3217%36%38%2
126
16th to endDay
48%22%34%20%9%
96
January1st to 15thNight
9%16%10%26%25%12%
780
16th to endNight
9%16%13%27%24%9%
832
February1st to 15thNight
6%16%11%27%26%10%
764
16th to endNight
11%16%14%26%23%7%
660
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%
717
16th to endNight
18%19%44%34%
764
September1st to 15thNight
38%312%48%24%
720
16th to endNight
8%5%17%46%20%
716
October1st to 15thNight
38%7%22%45%11%
720
16th to endNight
38%10%25%36%15%
768
November1st to 15thNight
213%11%29%30%11%
760
16th to endNight
5%17%9%26%30%11%
780
December1st to 15thNight
5%17%10%29%28%8%
780
16th to endNight
9%18%12%29%22%6%
832
Page generated at 2018-02-23 08:21:32. Version ac04

Copyright 2018 A. Danko


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