Torrance
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Torrance clear sky chart from 2005-11-05 to 2018-02-14.

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
64%
16500
31%
48670
25%
16448
70%
16448
39%
25768

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
60%
776
27%
2657
24%
776
69%
776
33%
1338
January16th to endNight
57%
832
35%
2542
27%
832
68%
832
36%
1323
February1st to 15thNight
61%
756
34%
2269
32%
752
67%
752
38%
1193
February16th to endNight
52%
632
27%
1895
22%
632
61%
632
28%
1117
March1st to 15thNight
60%
720
29%
2160
26%
720
68%
720
39%
1124
March16th to endNight
59%
768
26%
2000
20%
768
63%
768
37%
1179
April1st to 15thNight
57%
719
28%
1799
17%
719
62%
719
42%
1032
April16th to endNight
59%
720
30%
1800
15%
720
64%
720
41%
1031
May1st to 15thNight
59%
638
26%
1718
15%
638
62%
638
36%
1005
May16th to endNight
64%
561
26%
1685
17%
561
69%
561
38%
924
June1st to 15thNight
67%
468
23%
1548
19%
468
69%
468
32%
868
June16th to endNight
67%
360
28%
1440
29%
360
71%
360
30%
723
July1st to 15thNight
71%
340
28%
1360
31%
340
73%
340
34%
635
July16th to endNight
68%
653
23%
1671
16%
609
75%
609
41%
943
August1st to 15thNight
73%
717
30%
1790
20%
713
74%
713
45%
1029
August16th to endNight
78%
764
35%
1910
21%
764
81%
764
49%
1046
September1st to 15thNight
77%
720
34%
1821
26%
720
79%
720
50%
987
September16th to endNight
77%
716
39%
1980
35%
716
82%
716
54%
962
October1st to 15thNight
72%
720
34%
2004
33%
720
74%
720
48%
1040
October16th to endNight
72%
768
39%
2315
37%
768
79%
768
46%
1131
November1st to 15thNight
69%
760
33%
2470
34%
760
74%
760
44%
1137
November16th to endNight
64%
780
35%
2535
33%
780
73%
780
37%
1252
December1st to 15thNight
56%
780
32%
2535
28%
780
64%
780
32%
1334
December16th to endNight
52%
832
33%
2766
27%
832
64%
832
32%
1415

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
4312212346%65%
49374
Night
5%423313347%59%
48877
TransparencyDay
22%26%18%26%22%
49069
Night
25%36%16%24%22%
48682
SeeingDay
5%11%16%35%24%6%
6470
Night
7%15%6%23%34%13%
16511

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
7%423323246%58%
1607
16th to endDay
10%423312336%58%
2029
February1st to 15thDay
6%313313346%62%
1883
16th to endDay
10%5%13323347%53%
1579
March1st to 15thDay
331322345%7%61%
1800
16th to endDay
441332445%9%57%
2221
April1st to 15thDay
4412323247%62%
2149
16th to endDay
3212212236%69%
2160
May1st to 15thDay
45%22212347%63%
2232
16th to endDay
4413312337%64%
2429
June1st to 15thDay
6%6%24211338%59%
2408
16th to endDay
231211213474%
2520
July1st to 15thDay
3413212346%65%
2520
16th to endDay
2212213347%68%
2374
August1st to 15thDay
2311112235%74%
2160
16th to endDay
111212346%74%
2292
September1st to 15thDay
2212312236%71%
2137
16th to endDay
2312112246%73%
1980
October1st to 15thDay
5%222212245%66%
1953
16th to endDay
3212213345%69%
1908
November1st to 15thDay
3212323337%66%
1719
16th to endDay
4313322348%62%
1755
December1st to 15thDay
6%41232245%7%58%
1755
16th to endDay
9%213312347%58%
1804
January1st to 15thNight
7%413323448%56%
2657
16th to endNight
9%413213236%60%
2542
February1st to 15thNight
6%414323236%60%
2269
16th to endNight
11%5%34423445%51%
1895
March1st to 15thNight
5%42322235%9%57%
2160
16th to endNight
5%5%3332445%8%53%
2000
April1st to 15thNight
7%5%32212237%60%
1799
16th to endNight
45%23313346%62%
1800
May1st to 15thNight
6%6%24413338%55%
1718
16th to endNight
45%13323347%60%
1684
June1st to 15thNight
36%2432445%9%52%
1548
16th to endNight
27%333235%5%8%55%
1440
July1st to 15thNight
34244233410%55%
1440
16th to endNight
45%244245%5%9%52%
1789
August1st to 15thNight
35%2331235%10%57%
1800
16th to endNight
15%122125%5%10%60%
1910
September1st to 15thNight
141431345%9%61%
1821
16th to endNight
2413212236%69%
1980
October1st to 15thNight
3214313335%66%
2004
16th to endNight
4412212246%66%
2315
November1st to 15thNight
2322212347%66%
2470
16th to endNight
341331225%7%62%
2535
December1st to 15thNight
6%424423346%58%
2535
16th to endNight
10%313313236%59%
2766

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
28%36%15%21%24%
1607
16th to endDay
27%27%18%16%27%
2029
February1st to 15thDay
24%25%16%27%23%
1883
16th to endDay
31%37%22%24%10%
1579
March1st to 15thDay
22%311%20%21%19%
1800
16th to endDay
26%311%25%19%13%
2221
April1st to 15thDay
23%212%26%23%11%
2149
16th to endDay
19%210%24%26%16%
2160
May1st to 15thDay
24%39%23%24%15%
2232
16th to endDay
24%37%28%27%8%
2432
June1st to 15thDay
28%26%16%31%13%
2408
16th to endDay
20%139%30%34%
2520
July1st to 15thDay
23%3311%27%30%
2371
16th to endDay
21%37%20%31%16%
2229
August1st to 15thDay
17%2215%34%27%
2146
16th to endDay
16%3313%38%25%
2292
September1st to 15thDay
20%2412%31%28%
2137
16th to endDay
18%2115%33%28%
1980
October1st to 15thDay
21%26%19%26%24%
1953
16th to endDay
18%35%18%20%33%
1908
November1st to 15thDay
20%27%17%21%30%
1719
16th to endDay
22%27%16%20%29%
1755
December1st to 15thDay
25%39%17%19%25%
1755
16th to endDay
27%210%15%22%21%
1804
January1st to 15thNight
25%38%14%21%25%
2657
16th to endNight
26%27%16%16%29%
2542
February1st to 15thNight
26%26%17%22%24%
2280
16th to endNight
34%35%16%24%14%
1895
March1st to 15thNight
24%38%20%24%18%
2160
16th to endNight
28%410%21%21%12%
2000
April1st to 15thNight
26%29%26%23%12%
1799
16th to endNight
25%37%23%22%17%
1800
May1st to 15thNight
30%28%20%23%13%
1719
16th to endNight
26%49%24%26%9%
1685
June1st to 15thNight
31%49%14%28%11%
1548
16th to endNight
29%338%27%27%
1440
July1st to 15thNight
24%3411%26%30%
1360
16th to endNight
27%39%20%22%16%
1671
August1st to 15thNight
25%3212%34%21%
1790
16th to endNight
20%4211%36%24%
1910
September1st to 15thNight
21%349%31%29%
1821
16th to endNight
17%2115%32%30%
1980
October1st to 15thNight
21%3416%29%23%
2004
16th to endNight
20%2413%21%36%
2315
November1st to 15thNight
20%26%18%19%31%
2470
16th to endNight
23%35%16%21%29%
2535
December1st to 15thNight
29%26%14%20%25%
2535
16th to endNight
27%27%17%23%20%
2766

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
10%8%17%35%20%6%
145
16th to endDay
10%15%17%30%21%4
341
February1st to 15thDay
9%13%19%27%22%8%
320
16th to endDay
10%16%27%28%15%2
238
March1st to 15thDay
6%17%24%27%19%4
270
16th to endDay
5%18%24%34%12%5%
288
April1st to 15thDay
421%24%32%13%4
269
16th to endDay
219%32%32%7%4
270
May1st to 15thDay
415%26%35%14%3
288
16th to endDay
6%13%22%42%12%3
330
June1st to 15thDay
8%11%19%37%20%2
315
16th to endDay
19%8%42%29%7%
315
July1st to 15thDay
27%7%39%34%8%
305
16th to endDay
29%333%39%10%
327
August1st to 15thDay
36%6%43%33%6%
315
16th to endDay
15%6%34%43%8%
332
September1st to 15thDay
26%8%46%31%5%
315
16th to endDay
26%10%45%26%8%
315
October1st to 15thDay
5%6%20%38%24%4
315
16th to endDay
47%15%34%27%11%
324
November1st to 15thDay
5%29%33%33%15%
135
16th to endDay
27%8%34%34%12%
135
December1st to 15thDay
3213%32%34%12%
135
16th to endDay
7%6%18%21%35%10%
128
January1st to 15thNight
8%16%7%32%28%7%
780
16th to endNight
10%16%9%27%29%6%
832
February1st to 15thNight
6%17%7%28%30%9%
760
16th to endNight
13%17%8%28%25%6%
632
March1st to 15thNight
5%18%9%33%26%6%
720
16th to endNight
6%18%9%28%30%7%
768
April1st to 15thNight
7%19%9%29%27%5%
719
16th to endNight
6%20%9%26%30%7%
720
May1st to 15thNight
8%18%9%23%32%8%
639
16th to endNight
418%7%31%30%7%
563
June1st to 15thNight
418%5%27%36%8%
468
16th to endNight
6%16%214%43%15%
360
July1st to 15thNight
6%12%15%38%35%
340
16th to endNight
6%16%17%38%30%
653
August1st to 15thNight
7%9%112%43%25%
717
16th to endNight
5%8%17%44%32%
764
September1st to 15thNight
48%214%44%24%
720
16th to endNight
5%8%318%45%18%
716
October1st to 15thNight
5%8%6%22%43%14%
720
16th to endNight
6%9%6%19%38%19%
768
November1st to 15thNight
313%5%28%35%13%
760
16th to endNight
7%16%5%25%33%11%
780
December1st to 15thNight
8%16%8%30%27%7%
780
16th to endNight
12%18%11%27%23%6%
832
Page generated at 2018-02-15 07:58:38. Version ac04

Copyright 2018 A. Danko


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