Lake Thunderbird
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Thunderbird clear sky chart from 2005-11-05 to 2017-09-21.

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
39%
15970
19%
46899
12%
15927
46%
15927
26%
30421

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
22%
900
16%
2506
6%
895
31%
895
21%
1756
January16th to endNight
23%
960
14%
2589
5%
960
30%
960
18%
1878
February1st to 15thNight
23%
836
14%
2247
3%
836
31%
836
20%
1596
February16th to endNight
25%
631
19%
1893
7%
631
34%
631
20%
1280
March1st to 15thNight
29%
710
16%
2150
8%
710
35%
710
21%
1467
March16th to endNight
30%
576
15%
2002
10%
576
38%
576
19%
1352
April1st to 15thNight
30%
539
17%
1797
11%
539
40%
539
22%
1159
April16th to endNight
36%
540
18%
1791
13%
540
45%
540
23%
1158
May1st to 15thNight
36%
540
18%
1554
10%
540
44%
540
23%
1072
May16th to endNight
49%
563
20%
1497
12%
561
55%
561
34%
952
June1st to 15thNight
59%
540
18%
1440
12%
540
61%
540
37%
895
June16th to endNight
52%
540
18%
1440
10%
540
57%
540
36%
896
July1st to 15thNight
65%
510
18%
1360
13%
510
67%
510
42%
798
July16th to endNight
73%
564
25%
1417
18%
531
76%
531
45%
801
August1st to 15thNight
73%
539
23%
1617
23%
536
74%
536
42%
858
August16th to endNight
70%
573
23%
1910
23%
573
74%
573
36%
1049
September1st to 15thNight
63%
540
30%
1800
31%
540
69%
540
37%
960
September16th to endNight
58%
650
28%
1850
19%
650
63%
650
37%
1062
October1st to 15thNight
48%
660
29%
1948
20%
660
56%
660
35%
1129
October16th to endNight
32%
704
20%
2192
11%
704
43%
704
25%
1384
November1st to 15thNight
34%
700
25%
2276
16%
700
46%
700
27%
1346
November16th to endNight
28%
795
19%
2415
10%
795
37%
795
22%
1590
December1st to 15thNight
22%
900
14%
2520
6%
900
29%
900
18%
1846
December16th to endNight
18%
960
12%
2688
3%
960
26%
960
13%
2137

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
14%7%35%5%3445%7%38%
47969
Night
14%7%35%424446%41%
47068
Cloud CoverDay
13%7%35%5%3445%7%38%
47977
Night
13%7%35%5%24446%41%
47073
TransparencyDay
45%312%23%12%1
47655
Night
43%311%24%14%2
46900
SeeingDay
14%6%24%27%19%6%
5984
Night
17%7%28%31%13%1
15973

By Month

Percentage Cloud Cover NE (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
15%12%47%6%5%45%47%26%
1432
16th to endDay
13%15%6%8%7%33435%27%
1632
February1st to 15thDay
15%12%48%5%25%445%31%
1615
16th to endDay
14%8%48%7%2445%6%32%
1580
March1st to 15thDay
15%11%5%6%5%24346%33%
1811
16th to endDay
17%9%36%6%345%47%29%
2221
April1st to 15thDay
18%9%46%5%23346%36%
2151
16th to endDay
21%7%15%5%34446%34%
2166
May1st to 15thDay
20%7%26%5%3446%7%31%
2396
16th to endDay
16%6%35%4345%6%6%36%
2617
June1st to 15thDay
12%425%5%25%5%6%7%43%
2520
16th to endDay
10%325%6%46%5%6%7%40%
2520
July1st to 15thDay
8%324435%5%6%10%45%
2520
16th to endDay
7%4245%35%5%7%9%44%
2655
August1st to 15thDay
6%425%5%45%47%10%43%
2331
16th to endDay
10%42443445%8%47%
2292
September1st to 15thDay
12%32332345%7%49%
2160
16th to endDay
9%5%25%43445%7%48%
1890
October1st to 15thDay
14%6%25%42235%447%
1680
16th to endDay
18%6%25%5%24345%40%
1680
November1st to 15thDay
15%7%25%32345%5%44%
1582
16th to endDay
19%8%46%424235%38%
1542
December1st to 15thDay
18%12%46%6%35%445%28%
1440
16th to endDay
21%12%5%7%5%34345%25%
1536
January1st to 15thNight
15%9%37%5%2435%6%35%
2506
16th to endNight
11%12%6%8%6%35%446%32%
2589
February1st to 15thNight
14%10%47%5%34346%35%
2245
16th to endNight
15%8%46%5%23435%38%
1893
March1st to 15thNight
17%8%36%5%34435%38%
2137
16th to endNight
16%8%37%5%345%5%7%32%
2002
April1st to 15thNight
16%8%36%5%24347%39%
1797
16th to endNight
19%7%245%2335%6%38%
1791
May1st to 15thNight
18%5%25%43435%7%36%
1554
16th to endNight
9%4245%35%5%7%7%44%
1496
June1st to 15thNight
10%5%2442335%6%50%
1440
16th to endNight
8%325%5%245%6%9%45%
1440
July1st to 15thNight
7%3144345%5%9%51%
1440
16th to endNight
4313435%5%6%9%52%
1513
August1st to 15thNight
33235%2345%8%55%
1626
16th to endNight
7%42432445%7%53%
1910
September1st to 15thNight
12%312323346%56%
1800
16th to endNight
7%414325%5%6%8%49%
1850
October1st to 15thNight
11%414413445%53%
1948
16th to endNight
17%7%24422345%43%
2192
November1st to 15thNight
13%6%34413346%49%
2276
16th to endNight
17%7%35%433346%40%
2415
December1st to 15thNight
20%10%47%434335%32%
2520
16th to endNight
22%13%47%6%3423425%
2688

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
15%12%47%7%5%5%446%26%
1432
16th to endDay
13%16%6%8%7%34345%27%
1632
February1st to 15thDay
15%12%49%5%25%445%31%
1615
16th to endDay
14%9%5%8%6%24446%32%
1580
March1st to 15thDay
15%10%5%6%424346%33%
1821
16th to endDay
17%9%36%6%445%5%7%29%
2219
April1st to 15thDay
17%10%5%6%423346%35%
2151
16th to endDay
20%8%25%5%34346%34%
2166
May1st to 15thDay
19%7%36%5%3445%7%30%
2396
16th to endDay
15%6%36%5%35%5%5%6%36%
2617
June1st to 15thDay
11%5%25%5%35%5%5%7%42%
2520
16th to endDay
9%426%5%36%6%6%8%39%
2520
July1st to 15thDay
7%415%425%46%10%45%
2520
16th to endDay
6%5%145%36%5%6%9%43%
2655
August1st to 15thDay
5%4345%45%5%7%10%43%
2331
16th to endDay
9%42443446%8%46%
2292
September1st to 15thDay
12%42343335%7%49%
2160
16th to endDay
9%5%245%3445%8%47%
1890
October1st to 15thDay
13%6%25%323445%47%
1680
16th to endDay
18%7%25%5%34345%40%
1680
November1st to 15thDay
14%7%244235%5%5%44%
1582
16th to endDay
18%10%46%42333439%
1542
December1st to 15thDay
18%11%5%7%6%26%435%28%
1440
16th to endDay
21%12%5%7%5%24445%24%
1536
January1st to 15thNight
14%9%47%6%2335%6%35%
2506
16th to endNight
12%11%6%8%6%34446%31%
2589
February1st to 15thNight
14%10%5%6%5%34346%34%
2238
16th to endNight
15%8%5%6%5%23345%38%
1893
March1st to 15thNight
17%9%35%5%3344438%
2150
16th to endNight
17%8%36%6%335%5%7%32%
2002
April1st to 15thNight
15%9%35%424336%39%
1797
16th to endNight
18%8%345%24347%37%
1791
May1st to 15thNight
18%5%25%5%35%45%7%36%
1553
16th to endNight
9%4245%35%5%7%8%43%
1496
June1st to 15thNight
10%6%2443345%5%50%
1440
16th to endNight
8%425%5%345%6%9%45%
1440
July1st to 15thNight
7%31442446%9%52%
1440
16th to endNight
3224425%5%7%9%51%
1513
August1st to 15thNight
33145%2345%8%55%
1626
16th to endNight
7%5%1432445%7%52%
1910
September1st to 15thNight
11%312313446%56%
1800
16th to endNight
7%4244245%6%8%49%
1850
October1st to 15thNight
11%424414346%52%
1948
16th to endNight
17%7%24423345%43%
2192
November1st to 15thNight
12%6%24323345%48%
2276
16th to endNight
17%7%36%423346%40%
2415
December1st to 15thNight
19%11%48%42433432%
2520
16th to endNight
22%14%48%6%3433424%
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
58%312%15%9%
1433
16th to endDay
60%211%16%8%
1632
February1st to 15thDay
56%214%19%5%1
1617
16th to endDay
52%312%23%6%1
1580
March1st to 15thDay
51%315%21%7%
1821
16th to endDay
52%414%22%5%1
2221
April1st to 15thDay
50%211%23%11%
2151
16th to endDay
50%312%17%13%2
2166
May1st to 15thDay
51%312%23%7%
2396
16th to endDay
46%5%11%20%15%1
2621
June1st to 15thDay
38%412%27%16%1
2520
16th to endDay
39%6%11%22%17%2
2520
July1st to 15thDay
34%413%27%16%2
2371
16th to endDay
34%5%16%26%14%2
2488
August1st to 15thDay
32%5%15%27%16%1
2316
16th to endDay
33%5%12%28%16%3
2292
September1st to 15thDay
33%210%25%21%4
2160
16th to endDay
35%211%29%18%2
1890
October1st to 15thDay
37%39%29%17%1
1680
16th to endDay
46%213%24%11%2
1680
November1st to 15thDay
40%211%26%15%2
1582
16th to endDay
50%214%24%8%
1542
December1st to 15thDay
58%313%17%6%
1440
16th to endDay
61%410%13%8%
1536
January1st to 15thNight
50%313%19%12%
2506
16th to endNight
54%215%18%8%
2589
February1st to 15thNight
51%312%21%10%1
2247
16th to endNight
49%212%24%10%
1893
March1st to 15thNight
49%312%22%9%2
2150
16th to endNight
50%314%21%8%1
2002
April1st to 15thNight
46%29%25%13%2
1797
16th to endNight
46%212%22%10%5%
1791
May1st to 15thNight
47%410%23%14%
1554
16th to endNight
35%5%14%24%17%2
1498
June1st to 15thNight
34%312%24%21%3
1440
16th to endNight
34%5%13%21%20%4
1440
July1st to 15thNight
29%413%31%18%3
1360
16th to endNight
26%414%31%18%4
1417
August1st to 15thNight
26%314%32%19%3
1617
16th to endNight
30%411%28%20%4
1910
September1st to 15thNight
29%37%28%25%5%
1800
16th to endNight
30%410%30%20%3
1850
October1st to 15thNight
33%29%27%23%3
1948
16th to endNight
42%29%27%15%1
2192
November1st to 15thNight
37%39%26%18%4
2276
16th to endNight
46%211%25%13%
2415
December1st to 15thNight
55%211%21%8%
2520
16th to endNight
64%38%15%6%
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
31%12%28%21%5%1
90
16th to endDay
18%16%36%14%13%
96
February1st to 15thDay
17%11%50%15%5%
90
16th to endDay
16%14%33%19%14%1
81
March1st to 15thDay
28%21%30%15%31
90
16th to endDay
25%12%28%21%10%1
205
April1st to 15thDay
19%10%31%26%11%1
270
16th to endDay
23%6%25%26%15%2
270
May1st to 15thDay
22%9%30%25%9%2
353
16th to endDay
20%8%25%25%14%5%
517
June1st to 15thDay
10%327%32%20%5%
495
16th to endDay
11%7%31%26%17%5%
495
July1st to 15thDay
10%320%31%23%10%
475
16th to endDay
7%216%32%29%11%
515
August1st to 15thDay
6%312%33%28%14%
438
16th to endDay
9%212%30%31%14%
332
September1st to 15thDay
11%211%31%32%10%
315
16th to endDay
7%417%28%34%7%
275
October1st to 15thDay
12%11%23%25%20%7%
120
16th to endDay
21%441%23%8%
96
November1st to 15thDay
312%26%28%18%10%
90
16th to endDay
36%14%23%17%7%
90
December1st to 15thDay
20%15%30%30%4
90
16th to endDay
30%16%45%5%2
96
January1st to 15thNight
18%13%39%22%5%
900
16th to endNight
17%12%36%28%4
960
February1st to 15thNight
20%8%37%26%5%
839
16th to endNight
19%11%36%26%6%
631
March1st to 15thNight
22%9%33%28%5%
710
16th to endNight
20%8%34%27%8%
576
April1st to 15thNight
20%10%34%28%6%
539
16th to endNight
21%7%28%32%9%
540
May1st to 15thNight
21%6%28%33%9%
540
16th to endNight
11%328%40%15%
563
June1st to 15thNight
11%319%49%15%
540
16th to endNight
9%326%40%18%1
540
July1st to 15thNight
7%215%43%28%3
510
16th to endNight
4111%46%31%3
564
August1st to 15thNight
5%19%43%32%7%
539
16th to endNight
10%110%38%34%4
573
September1st to 15thNight
13%413%36%28%4
540
16th to endNight
9%5%20%32%30%2
650
October1st to 15thNight
14%5%24%32%21%1
660
16th to endNight
23%8%31%27%9%
704
November1st to 15thNight
16%9%34%27%10%1
700
16th to endNight
21%11%32%26%7%
795
December1st to 15thNight
25%12%31%24%5%
900
16th to endNight
30%10%32%22%3
960
Page generated at 2017-09-22 06:35:31. Version ac04

Copyright 2017 A. Danko


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