Long Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Beach clear sky chart from 2005-11-05 to 2018-03-21.

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
73%
16659
30%
49058
28%
16611
76%
16611
44%
26226

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
71%
776
27%
2664
27%
776
76%
776
41%
1324
January16th to endNight
66%
832
35%
2512
31%
832
72%
832
44%
1315
February1st to 15thNight
71%
757
33%
2281
34%
756
75%
756
43%
1213
February16th to endNight
62%
684
28%
2051
29%
684
66%
684
35%
1188
March1st to 15thNight
67%
780
27%
2340
28%
780
72%
780
42%
1259
March16th to endNight
69%
792
26%
2071
22%
792
72%
792
41%
1227
April1st to 15thNight
67%
719
28%
1799
18%
719
70%
719
46%
1053
April16th to endNight
69%
720
28%
1800
17%
720
71%
720
47%
1042
May1st to 15thNight
67%
630
25%
1710
17%
630
68%
630
39%
1035
May16th to endNight
73%
561
25%
1685
19%
561
75%
561
42%
941
June1st to 15thNight
75%
489
22%
1569
20%
489
76%
489
35%
906
June16th to endNight
74%
360
26%
1440
30%
360
74%
360
31%
746
July1st to 15thNight
83%
340
29%
1360
34%
340
83%
340
39%
630
July16th to endNight
80%
662
23%
1681
17%
619
80%
619
42%
976
August1st to 15thNight
80%
717
29%
1790
19%
713
80%
713
49%
1028
August16th to endNight
83%
764
34%
1910
23%
764
83%
764
54%
1045
September1st to 15thNight
82%
720
31%
1827
26%
720
83%
720
51%
1017
September16th to endNight
83%
716
38%
1980
38%
716
83%
716
57%
973
October1st to 15thNight
77%
720
33%
1993
33%
720
80%
720
51%
1043
October16th to endNight
80%
768
38%
2322
41%
768
81%
768
50%
1129
November1st to 15thNight
80%
760
33%
2470
36%
760
83%
760
50%
1148
November16th to endNight
76%
780
35%
2535
39%
780
79%
780
45%
1239
December1st to 15thNight
69%
780
32%
2535
32%
780
73%
780
39%
1330
December16th to endNight
63%
832
33%
2733
31%
832
69%
832
38%
1419

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
4312212347%64%
49753
Night
5%5%23313347%60%
49264
TransparencyDay
21%38%18%25%22%
49447
Night
25%37%16%23%22%
49070
SeeingDay
5%420%39%23%6%
6613
Night
7%18%29%38%13%
16673

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%423313336%59%
1601
16th to endDay
9%423223236%58%
2058
February1st to 15thDay
6%313323336%61%
1901
16th to endDay
9%413323247%55%
1709
March1st to 15thDay
5%21232347%8%59%
1950
16th to endDay
441332345%8%56%
2276
April1st to 15thDay
5%313312338%62%
2149
16th to endDay
3312212237%68%
2160
May1st to 15thDay
45%22112338%62%
2238
16th to endDay
4413212238%63%
2429
June1st to 15thDay
6%6%23211247%59%
2387
16th to endDay
2412112226%71%
2520
July1st to 15thDay
45%12212348%63%
2520
16th to endDay
231221325%7%66%
2363
August1st to 15thDay
231211137%74%
2160
16th to endDay
122112248%72%
2292
September1st to 15thDay
2212212237%71%
2131
16th to endDay
232111236%72%
1980
October1st to 15thDay
5%312212346%66%
1965
16th to endDay
3213212346%68%
1902
November1st to 15thDay
3312213336%67%
1719
16th to endDay
5%212313346%63%
1755
December1st to 15thDay
6%423222447%58%
1755
16th to endDay
9%313313238%58%
1833
January1st to 15thNight
6%42332245%7%58%
2664
16th to endNight
9%412212236%61%
2512
February1st to 15thNight
6%5%24323236%60%
2281
16th to endNight
11%5%23323445%53%
2051
March1st to 15thNight
6%5%2331335%9%56%
2340
16th to endNight
46%2432446%7%54%
2071
April1st to 15thNight
7%5%23212236%60%
1799
16th to endNight
46%3321235%5%61%
1800
May1st to 15thNight
8%6%23322248%55%
1710
16th to endNight
6%6%23212147%61%
1684
June1st to 15thNight
47%2331336%9%53%
1569
16th to endNight
38%4441335%7%55%
1440
July1st to 15thNight
35%1421335%10%57%
1440
16th to endNight
45%2432445%11%52%
1798
August1st to 15thNight
46%23212448%59%
1800
16th to endNight
15%2221335%9%61%
1910
September1st to 15thNight
2323313348%61%
1827
16th to endNight
25%12211247%68%
1980
October1st to 15thNight
3423213235%66%
1993
16th to endNight
4312212236%67%
2322
November1st to 15thNight
341221225%7%66%
2470
16th to endNight
4412312348%62%
2535
December1st to 15thNight
7%413423245%58%
2535
16th to endNight
9%413312245%60%
2733

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
27%37%15%20%25%
1601
16th to endDay
28%36%18%15%27%
2058
February1st to 15thDay
24%36%16%25%23%
1901
16th to endDay
29%47%21%25%12%
1709
March1st to 15thDay
22%413%21%19%19%
1950
16th to endDay
24%5%13%24%19%13%
2276
April1st to 15thDay
23%412%26%23%10%
2149
16th to endDay
18%410%23%25%16%
2160
May1st to 15thDay
22%410%22%24%14%
2238
16th to endDay
22%5%9%29%25%7%
2432
June1st to 15thDay
26%5%6%16%31%13%
2387
16th to endDay
18%2410%30%33%
2520
July1st to 15thDay
21%36%11%27%29%
2371
16th to endDay
19%39%21%30%15%
2217
August1st to 15thDay
16%2316%33%27%
2146
16th to endDay
14%25%14%38%24%
2292
September1st to 15thDay
18%26%12%32%27%
2131
16th to endDay
16%25%14%32%29%
1980
October1st to 15thDay
21%26%19%25%25%
1965
16th to endDay
18%46%16%20%34%
1902
November1st to 15thDay
19%39%17%20%30%
1719
16th to endDay
21%48%15%21%29%
1755
December1st to 15thDay
24%49%17%18%25%
1755
16th to endDay
26%49%16%21%22%
1833
January1st to 15thNight
25%310%14%21%25%
2664
16th to endNight
25%38%17%16%29%
2512
February1st to 15thNight
26%36%16%21%25%
2292
16th to endNight
32%47%14%24%16%
2051
March1st to 15thNight
27%38%19%22%17%
2340
16th to endNight
28%412%22%19%12%
2071
April1st to 15thNight
27%39%25%22%11%
1799
16th to endNight
26%310%22%21%16%
1800
May1st to 15thNight
32%48%20%22%12%
1711
16th to endNight
26%5%10%25%22%9%
1685
June1st to 15thNight
32%5%11%14%26%10%
1569
16th to endNight
32%25%9%25%24%
1440
July1st to 15thNight
24%36%12%27%25%
1360
16th to endNight
29%39%20%23%13%
1681
August1st to 15thNight
26%2413%34%17%
1790
16th to endNight
21%36%12%34%22%
1910
September1st to 15thNight
22%46%8%31%26%
1827
16th to endNight
19%1314%31%28%
1980
October1st to 15thNight
22%35%16%28%23%
1993
16th to endNight
20%36%13%21%35%
2322
November1st to 15thNight
19%37%18%18%32%
2470
16th to endNight
22%37%16%20%29%
2535
December1st to 15thNight
28%27%14%19%26%
2535
16th to endNight
27%38%15%23%21%
2733

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%222%41%17%5%
139
16th to endDay
12%6%23%35%17%5%
348
February1st to 15thDay
9%425%30%22%8%
326
16th to endDay
10%11%26%30%18%2
290
March1st to 15thDay
9%9%30%29%18%3
330
16th to endDay
5%9%28%38%13%3
311
April1st to 15thDay
5%12%31%33%13%4
269
16th to endDay
29%40%35%7%4
270
May1st to 15thDay
5%8%27%38%15%3
288
16th to endDay
6%6%26%40%16%4
330
June1st to 15thDay
8%225%37%22%2
315
16th to endDay
112%47%29%8%
315
July1st to 15thDay
39%46%32%7%
305
16th to endDay
36%42%34%13%
327
August1st to 15thDay
319%49%30%6%
315
16th to endDay
28%44%37%6%
332
September1st to 15thDay
314%51%25%4
315
16th to endDay
2218%48%19%8%
315
October1st to 15thDay
5%227%40%20%3
315
16th to endDay
4219%36%27%9%
318
November1st to 15thDay
4314%33%30%14%
135
16th to endDay
26%14%33%31%11%
135
December1st to 15thDay
3313%36%32%10%
135
16th to endDay
7%420%23%37%7%
135
January1st to 15thNight
7%112%38%33%6%
780
16th to endNight
10%113%33%33%7%
832
February1st to 15thNight
7%29%35%35%9%
764
16th to endNight
13%311%37%28%5%
684
March1st to 15thNight
8%212%40%28%7%
780
16th to endNight
7%210%34%35%7%
792
April1st to 15thNight
9%412%36%31%5%
719
16th to endNight
6%311%35%35%7%
720
May1st to 15thNight
11%112%32%34%8%
631
16th to endNight
6%211%35%36%8%
563
June1st to 15thNight
5%38%33%40%9%
489
16th to endNight
5%1318%53%16%
360
July1st to 15thNight
5%16%52%32%
340
16th to endNight
5%1213%45%31%
662
August1st to 15thNight
7%1116%48%24%
717
16th to endNight
5%110%49%33%
764
September1st to 15thNight
5%219%48%23%
720
16th to endNight
6%222%51%15%
716
October1st to 15thNight
5%7%29%45%11%
720
16th to endNight
6%15%26%42%17%
768
November1st to 15thNight
416%35%38%14%
760
16th to endNight
6%17%32%38%13%
780
December1st to 15thNight
9%110%35%34%8%
780
16th to endNight
12%313%35%27%7%
832
Page generated at 2018-03-22 08:34:22. Version ac04

Copyright 2018 A. Danko


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