White City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White City clear sky chart from 2005-11-05 to 2017-10-06.

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
61%
15543
24%
47188
20%
15502
66%
15502
34%
27559

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
40%
718
23%
2312
13%
716
52%
716
26%
1396
January16th to endNight
40%
768
25%
2304
16%
768
49%
768
26%
1480
February1st to 15thNight
44%
702
28%
2107
16%
699
55%
699
32%
1246
February16th to endNight
44%
631
25%
1893
15%
631
53%
631
31%
1140
March1st to 15thNight
50%
720
26%
2085
16%
720
58%
720
37%
1192
March16th to endNight
56%
768
27%
2112
18%
768
61%
768
41%
1210
April1st to 15thNight
57%
618
26%
1876
22%
618
63%
618
37%
1058
April16th to endNight
67%
540
31%
1800
27%
540
73%
540
42%
894
May1st to 15thNight
68%
539
28%
1637
25%
539
72%
539
45%
855
May16th to endNight
78%
561
27%
1682
24%
561
80%
561
46%
872
June1st to 15thNight
76%
540
17%
1620
16%
540
76%
540
37%
940
June16th to endNight
77%
540
18%
1620
17%
540
77%
540
36%
927
July1st to 15thNight
78%
510
11%
1530
12%
510
78%
510
32%
923
July16th to endNight
80%
564
12%
1644
13%
531
80%
531
30%
1026
August1st to 15thNight
76%
539
9%
1788
11%
536
77%
536
27%
1107
August16th to endNight
73%
573
15%
1910
18%
573
73%
573
25%
1189
September1st to 15thNight
72%
699
13%
1959
12%
699
72%
699
29%
1288
September16th to endNight
71%
717
24%
1980
22%
717
72%
717
33%
1238
October1st to 15thNight
68%
684
31%
1881
26%
684
72%
684
43%
1054
October16th to endNight
64%
704
32%
2040
29%
704
69%
704
38%
1162
November1st to 15thNight
62%
700
31%
2232
30%
700
69%
700
39%
1177
November16th to endNight
52%
720
29%
2340
24%
720
62%
720
35%
1276
December1st to 15thNight
50%
720
27%
2340
24%
720
58%
720
32%
1340
December16th to endNight
46%
768
22%
2496
20%
768
52%
768
24%
1569

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
9%425%5%35%5%6%9%41%
47993
Night
8%42442446%8%48%
47398
TransparencyDay
36%6%14%20%15%6%
47699
Night
32%5%14%21%17%8%
47196
SeeingDay
9%314%24%26%22%
5461
Night
10%416%28%31%9%
15550

By Month

Percentage Cloud Cover SE (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
11%435%43445%8%43%
1623
16th to endDay
13%5%25%5%34446%44%
1920
February1st to 15thDay
14%5%24423346%48%
1750
16th to endDay
13%5%24323336%50%
1580
March1st to 15thDay
7%31442345%9%53%
1875
16th to endDay
8%414334347%54%
2111
April1st to 15thDay
10%42442435%8%50%
2080
16th to endDay
7%32331435%8%55%
2160
May1st to 15thDay
5%31443446%9%51%
2313
16th to endDay
3323436%6%7%10%46%
2431
June1st to 15thDay
7%6%26%6%36%6%8%10%33%
2340
16th to endDay
8%425%7%47%7%10%12%30%
2340
July1st to 15thDay
8%436%8%48%8%10%11%23%
2340
16th to endDay
9%5%27%8%5%7%9%8%11%23%
2409
August1st to 15thDay
11%5%28%8%6%8%8%9%12%19%
2160
16th to endDay
9%6%37%6%48%6%8%11%28%
2292
September1st to 15thDay
8%6%37%7%47%8%10%10%24%
1989
16th to endDay
7%435%6%5%6%8%6%9%37%
1980
October1st to 15thDay
6%5%245%3435%8%50%
1877
16th to endDay
8%423424345%55%
1832
November1st to 15thDay
7%414323448%54%
1623
16th to endDay
8%324424447%54%
1620
December1st to 15thDay
12%6%23423347%49%
1620
16th to endDay
14%7%35%5%35%5%5%7%36%
1728
January1st to 15thNight
13%6%2432445%7%45%
2312
16th to endNight
15%7%24423446%42%
2304
February1st to 15thNight
14%5%23323345%52%
2103
16th to endNight
13%5%23424336%50%
1893
March1st to 15thNight
9%32432446%9%48%
2085
16th to endNight
9%313324347%55%
2112
April1st to 15thNight
7%42442446%7%51%
1876
16th to endNight
431242445%8%58%
1800
May1st to 15thNight
6%223323448%58%
1637
16th to endNight
32124245%5%11%55%
1682
June1st to 15thNight
5%3245%346%7%11%44%
1620
16th to endNight
5%3145%246%7%12%46%
1620
July1st to 15thNight
43145%35%6%10%13%41%
1620
16th to endNight
44235%46%7%10%15%37%
1756
August1st to 15thNight
5%415%5%36%7%10%14%35%
1800
16th to endNight
8%315%5%46%5%8%12%39%
1910
September1st to 15thNight
7%5%246%45%7%8%11%36%
1959
16th to endNight
6%435%435%5%8%10%43%
1980
October1st to 15thNight
33143245%5%7%55%
1881
16th to endNight
8%325%324335%55%
2040
November1st to 15thNight
6%423324446%57%
2232
16th to endNight
9%324424246%55%
2340
December1st to 15thNight
11%5%24324348%48%
2340
16th to endNight
13%6%25%5%3445%5%42%
2496

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
38%310%15%20%10%
1624
16th to endDay
39%39%14%21%10%
1920
February1st to 15thDay
37%26%18%22%12%
1752
16th to endDay
37%38%18%22%11%
1580
March1st to 15thDay
28%5%11%23%23%8%
1875
16th to endDay
28%312%25%19%10%
2112
April1st to 15thDay
32%49%22%21%10%
2080
16th to endDay
25%412%29%21%7%
2160
May1st to 15thDay
27%414%23%20%8%
2313
16th to endDay
27%6%19%27%16%3
2435
June1st to 15thDay
40%7%20%24%5%
2340
16th to endDay
40%9%21%21%6%
2340
July1st to 15thDay
45%11%25%15%1
2201
16th to endDay
45%11%24%16%2
2258
August1st to 15thDay
50%11%21%12%2
2148
16th to endDay
44%11%22%15%5%
2292
September1st to 15thDay
44%11%20%14%6%2
1989
16th to endDay
38%7%15%19%12%6%
1980
October1st to 15thDay
30%39%20%21%13%
1877
16th to endDay
29%36%15%27%17%
1832
November1st to 15thDay
28%28%21%24%14%
1623
16th to endDay
29%36%22%22%15%
1620
December1st to 15thDay
35%212%20%21%7%
1620
16th to endDay
45%49%18%15%6%
1728
January1st to 15thNight
38%49%15%21%10%
2312
16th to endNight
42%35%15%21%11%
2304
February1st to 15thNight
36%26%16%24%13%
2112
16th to endNight
36%37%17%21%13%
1893
March1st to 15thNight
30%411%23%21%8%
2085
16th to endNight
28%310%23%20%12%
2112
April1st to 15thNight
30%410%18%24%11%
1876
16th to endNight
23%5%10%30%21%9%
1800
May1st to 15thNight
23%413%23%23%11%
1638
16th to endNight
22%5%18%28%20%4
1684
June1st to 15thNight
29%6%23%31%8%
1620
16th to endNight
28%7%26%25%11%
1620
July1st to 15thNight
29%11%32%24%2
1530
16th to endNight
30%13%31%21%3
1644
August1st to 15thNight
32%12%34%17%3
1788
16th to endNight
33%12%26%21%41
1910
September1st to 15thNight
37%9%24%17%8%2
1959
16th to endNight
33%8%17%19%17%3
1980
October1st to 15thNight
25%5%10%19%24%14%
1881
16th to endNight
30%35%15%25%19%
2040
November1st to 15thNight
28%36%22%24%15%
2232
16th to endNight
30%38%17%21%18%
2340
December1st to 15thNight
35%39%24%21%6%
2340
16th to endNight
42%38%21%15%7%
2496

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
12%10%37%28%8%2
90
16th to endDay
16%17%33%27%5%
96
February1st to 15thDay
5%20%33%28%11%1
90
16th to endDay
9%8%43%28%9%
81
March1st to 15thDay
9%9%38%26%14%1
165
16th to endDay
11%426%31%23%2
288
April1st to 15thDay
10%8%25%27%22%4
270
16th to endDay
8%219%32%29%8%
270
May1st to 15thDay
6%5%16%30%25%15%
288
16th to endDay
5%18%25%29%29%
331
June1st to 15thDay
11%5%20%29%32%
315
16th to endDay
10%2215%27%40%
315
July1st to 15thDay
6%115%31%53%
305
16th to endDay
6%49%30%47%
326
August1st to 15thDay
12%15%13%30%37%
313
16th to endDay
7%1313%37%37%
332
September1st to 15thDay
12%27%22%27%27%
315
16th to endDay
7%15%25%38%21%
314
October1st to 15thDay
5%116%39%25%11%
278
16th to endDay
9%316%35%26%7%
272
November1st to 15thDay
12%121%41%16%6%
131
16th to endDay
18%31%37%15%5%
90
December1st to 15thDay
12%7%28%33%14%3
90
16th to endDay
20%6%28%32%10%2
96
January1st to 15thNight
15%10%29%30%14%1
720
16th to endNight
17%9%26%32%13%
768
February1st to 15thNight
14%9%26%35%13%1
704
16th to endNight
16%6%26%38%11%
631
March1st to 15thNight
10%6%28%35%17%
720
16th to endNight
10%422%36%24%1
768
April1st to 15thNight
10%420%38%25%1
618
16th to endNight
5%119%32%36%3
540
May1st to 15thNight
7%213%37%31%7%
540
16th to endNight
49%23%51%10%
563
June1st to 15thNight
7%1320%48%18%
540
16th to endNight
5%213%50%26%
540
July1st to 15thNight
5%119%43%38%
510
16th to endNight
48%50%34%
564
August1st to 15thNight
417%48%36%
539
16th to endNight
10%211%44%29%
573
September1st to 15thNight
9%2414%46%22%
699
16th to endNight
9%15%27%45%10%
717
October1st to 15thNight
5%116%32%38%5%
684
16th to endNight
9%315%34%32%4
704
November1st to 15thNight
8%317%39%26%3
700
16th to endNight
10%7%23%34%22%2
720
December1st to 15thNight
11%6%25%34%20%1
720
16th to endNight
16%6%24%34%17%
768
Page generated at 2017-10-07 14:07:44. Version ac04

Copyright 2017 A. Danko


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