Mansfield Dam
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mansfield Dam clear sky chart from 2005-11-05 to 2017-08-12.

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
49%
15324
26%
46550
18%
15278
57%
15278
34%
26969

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
38%
898
26%
2327
12%
895
45%
895
32%
1458
January16th to endNight
35%
906
30%
2442
13%
906
47%
906
33%
1503
February1st to 15thNight
33%
704
28%
2106
12%
698
46%
698
30%
1235
February16th to endNight
24%
632
29%
1894
8%
632
40%
632
30%
1103
March1st to 15thNight
32%
549
27%
1989
14%
549
47%
549
24%
1177
March16th to endNight
32%
576
24%
2112
15%
576
44%
576
25%
1216
April1st to 15thNight
29%
539
22%
1977
12%
539
44%
539
25%
1140
April16th to endNight
29%
540
25%
1761
12%
540
46%
540
25%
1089
May1st to 15thNight
35%
539
22%
1619
15%
539
45%
539
28%
998
May16th to endNight
48%
562
24%
1684
19%
561
58%
561
34%
995
June1st to 15thNight
66%
540
23%
1620
22%
540
73%
540
50%
803
June16th to endNight
67%
540
22%
1620
22%
540
71%
540
38%
935
July1st to 15thNight
74%
510
22%
1530
22%
510
79%
510
46%
804
July16th to endNight
80%
564
26%
1594
28%
531
84%
531
46%
835
August1st to 15thNight
89%
527
30%
1602
33%
524
89%
524
55%
755
August16th to endNight
76%
525
19%
1813
24%
525
77%
525
31%
1039
September1st to 15thNight
75%
495
21%
1815
24%
495
76%
495
30%
1047
September16th to endNight
70%
492
26%
1815
28%
492
73%
492
29%
1013
October1st to 15thNight
67%
513
33%
1833
31%
513
71%
513
37%
931
October16th to endNight
56%
704
35%
2112
22%
704
64%
704
47%
1076
November1st to 15thNight
51%
709
28%
2109
18%
709
57%
709
35%
1227
November16th to endNight
45%
900
30%
2340
15%
900
52%
900
37%
1419
December1st to 15thNight
38%
900
28%
2340
15%
900
44%
900
31%
1531
December16th to endNight
36%
960
24%
2496
11%
960
44%
960
29%
1640

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
12%5%2442445%7%46%
47410
Night
11%423323347%53%
46753
Cloud CoverDay
12%5%2442445%7%46%
47408
Night
11%423323347%53%
46753
TransparencyDay
37%5%10%19%18%9%
47108
Night
31%5%11%20%19%11%
46558
SeeingDay
12%5%19%32%24%5%
5282
Night
13%6%26%35%16%1
15328

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
16%423323325%51%
1611
16th to endDay
15%423422235%53%
1791
February1st to 15thDay
14%7%2421323453%
1750
16th to endDay
17%6%23222245%50%
1580
March1st to 15thDay
21%5%24313335%45%
1970
16th to endDay
15%5%24323346%48%
2112
April1st to 15thDay
12%6%25%42445%6%44%
1971
16th to endDay
13%6%34424446%44%
2196
May1st to 15thDay
15%6%35%6%3445%6%38%
2331
16th to endDay
14%6%25%5%35%6%6%7%36%
2430
June1st to 15thDay
4314436%6%7%8%47%
2340
16th to endDay
9%435%5%36%7%7%9%37%
2340
July1st to 15thDay
8%4245%45%7%7%8%41%
2340
16th to endDay
7%3245%35%5%6%9%46%
2466
August1st to 15thDay
221233435%10%59%
2259
16th to endDay
5%326%6%46%6%6%11%39%
2034
September1st to 15thDay
11%5%35%6%35%5%6%7%38%
1815
16th to endDay
9%425%5%345%6%7%46%
1815
October1st to 15thDay
11%324424247%53%
1785
16th to endDay
8%31222233465%
1760
November1st to 15thDay
12%6%25%423446%48%
1746
16th to endDay
14%5%24223235%54%
1620
December1st to 15thDay
18%6%25%312345%46%
1620
16th to endDay
15%6%24423435%45%
1728
January1st to 15thNight
16%5%24213335%51%
2327
16th to endNight
16%423313345%51%
2442
February1st to 15thNight
16%5%2331222455%
2102
16th to endNight
13%5%23223335%52%
1894
March1st to 15thNight
17%6%14323335%48%
1989
16th to endNight
13%423324346%50%
2112
April1st to 15thNight
12%5%24323346%49%
1977
16th to endNight
14%6%34423437%45%
1761
May1st to 15thNight
11%5%25%4245%5%8%46%
1619
16th to endNight
9%42332445%10%48%
1683
June1st to 15thNight
31222345%10%62%
1620
16th to endNight
6%31342446%10%53%
1620
July1st to 15thNight
5%21231346%13%55%
1620
16th to endNight
421232445%12%57%
1702
August1st to 15thNight
21111335%10%66%
1612
16th to endNight
6%225%435%5%7%9%48%
1813
September1st to 15thNight
8%4244335%6%9%47%
1815
16th to endNight
9%41443445%6%50%
1815
October1st to 15thNight
9%313222346%60%
1833
16th to endNight
8%312212335%64%
2112
November1st to 15thNight
10%42332435%6%54%
2109
16th to endNight
12%5%13322235%56%
2340
December1st to 15thNight
14%7%34313445%48%
2340
16th to endNight
16%7%3431343448%
2496

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
16%423323325%51%
1611
16th to endDay
15%423422335%53%
1791
February1st to 15thDay
14%7%2421323453%
1750
16th to endDay
16%6%23313245%50%
1580
March1st to 15thDay
21%5%24313335%45%
1970
16th to endDay
15%5%24313346%48%
2110
April1st to 15thDay
13%6%2442445%6%44%
1971
16th to endDay
13%6%35%424446%44%
2196
May1st to 15thDay
15%6%346%3445%6%38%
2331
16th to endDay
14%6%25%5%35%5%6%7%36%
2430
June1st to 15thDay
5%314436%7%7%8%48%
2340
16th to endDay
9%425%5%46%7%7%9%37%
2340
July1st to 15thDay
8%3245%45%6%8%8%41%
2340
16th to endDay
7%3245%345%6%9%46%
2466
August1st to 15thDay
121233445%10%59%
2259
16th to endDay
6%327%5%36%6%6%11%39%
2034
September1st to 15thDay
10%5%25%6%36%5%6%8%38%
1815
16th to endDay
9%425%5%245%6%7%46%
1815
October1st to 15thDay
10%423423336%53%
1785
16th to endDay
8%21322233465%
1760
November1st to 15thDay
11%6%25%423445%48%
1746
16th to endDay
14%5%24223235%54%
1620
December1st to 15thDay
18%7%2431334446%
1620
16th to endDay
15%7%24423435%45%
1728
January1st to 15thNight
16%5%24313335%51%
2327
16th to endNight
16%423313346%51%
2442
February1st to 15thNight
16%5%2321222455%
2102
16th to endNight
14%5%23323335%53%
1894
March1st to 15thNight
17%5%13323345%48%
1989
16th to endNight
13%423324346%49%
2112
April1st to 15thNight
12%5%24423446%49%
1977
16th to endNight
14%6%24423437%45%
1761
May1st to 15thNight
10%5%25%4245%5%7%46%
1619
16th to endNight
9%41332446%10%48%
1683
June1st to 15thNight
32222345%10%62%
1620
16th to endNight
6%21342445%10%53%
1620
July1st to 15thNight
5%11231346%13%55%
1620
16th to endNight
421231445%12%57%
1702
August1st to 15thNight
21111326%10%66%
1612
16th to endNight
5%325%425%5%7%9%47%
1813
September1st to 15thNight
8%42433446%9%47%
1815
16th to endNight
9%41443345%6%50%
1815
October1st to 15thNight
9%313222336%60%
1833
16th to endNight
8%312213335%64%
2112
November1st to 15thNight
10%41331435%6%54%
2109
16th to endNight
13%5%13322235%56%
2340
December1st to 15thNight
14%7%34313345%48%
2340
16th to endNight
16%6%3431333448%
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
36%36%18%21%12%
1612
16th to endDay
35%35%13%25%15%
1791
February1st to 15thDay
36%36%14%22%16%
1751
16th to endDay
38%36%18%20%13%
1580
March1st to 15thDay
42%37%12%21%12%
1970
16th to endDay
38%5%7%16%22%9%
2112
April1st to 15thDay
40%5%7%15%17%12%
1971
16th to endDay
41%5%6%18%17%11%
2196
May1st to 15thDay
45%5%9%13%17%7%
2331
16th to endDay
44%8%11%16%15%3
2434
June1st to 15thDay
31%7%12%22%20%5%
2340
16th to endDay
40%9%12%20%14%2
2340
July1st to 15thDay
35%8%15%25%13%1
2201
16th to endDay
31%7%18%28%12%
2311
August1st to 15thDay
19%7%17%35%18%1
2245
16th to endDay
37%10%16%23%10%2
2034
September1st to 15thDay
42%7%12%19%12%5%
1815
16th to endDay
35%7%10%18%19%9%
1815
October1st to 15thDay
33%48%19%18%15%
1785
16th to endDay
23%36%16%30%20%
1760
November1st to 15thDay
38%5%7%19%18%10%
1746
16th to endDay
35%26%12%21%21%
1620
December1st to 15thDay
42%28%16%20%9%
1620
16th to endDay
41%49%14%18%10%
1728
January1st to 15thNight
36%35%16%20%17%
2327
16th to endNight
35%35%15%22%17%
2442
February1st to 15thNight
34%35%14%22%20%
2112
16th to endNight
34%36%16%21%16%
1894
March1st to 15thNight
38%48%12%21%14%
1989
16th to endNight
36%410%15%21%11%
2112
April1st to 15thNight
37%48%16%17%16%
1977
16th to endNight
40%5%9%17%16%11%
1761
May1st to 15thNight
36%6%11%19%16%8%
1620
16th to endNight
30%7%16%25%15%3
1685
June1st to 15thNight
17%6%15%26%28%4
1620
16th to endNight
25%10%15%28%16%3
1620
July1st to 15thNight
20%7%23%33%14%1
1530
16th to endNight
20%7%25%35%11%
1594
August1st to 15thNight
13%7%21%36%18%1
1602
16th to endNight
30%9%21%25%10%2
1813
September1st to 15thNight
31%8%17%23%13%5%
1815
16th to endNight
32%6%13%20%17%9%
1815
October1st to 15thNight
26%5%10%23%19%14%
1833
16th to endNight
23%36%17%26%23%
2112
November1st to 15thNight
31%5%9%20%20%13%
2109
16th to endNight
32%36%14%20%22%
2340
December1st to 15thNight
39%48%17%20%10%
2340
16th to endNight
40%36%14%21%13%
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
20%8%36%26%7%
90
16th to endDay
15%14%38%22%7%1
96
February1st to 15thDay
10%17%35%28%6%1
90
16th to endDay
18%19%35%22%3
81
March1st to 15thDay
31%13%30%14%10%1
90
16th to endDay
12%8%38%32%7%1
96
April1st to 15thDay
13%13%43%23%6%
90
16th to endDay
15%13%38%21%10%
306
May1st to 15thDay
17%10%37%25%8%
468
16th to endDay
22%5%25%30%14%1
517
June1st to 15thDay
7%14%47%25%4
495
16th to endDay
8%113%38%27%9%
495
July1st to 15thDay
6%11%43%31%7%
475
16th to endDay
6%433%47%8%
515
August1st to 15thDay
3432%46%12%
444
16th to endDay
13%442%30%8%
202
September1st to 15thDay
36%20%54%15%
90
16th to endDay
7%221%47%21%
90
October1st to 15thDay
210%34%46%6%
90
16th to endDay
17%6%8%33%30%4
96
November1st to 15thDay
33%324%24%11%3
90
16th to endDay
26%10%26%25%8%2
90
December1st to 15thDay
21%5%31%21%12%8%
90
16th to endDay
20%20%32%21%31
96
January1st to 15thNight
19%11%27%31%9%
900
16th to endNight
18%9%33%32%6%
906
February1st to 15thNight
19%13%31%29%6%
704
16th to endNight
18%13%42%24%1
632
March1st to 15thNight
19%8%35%30%4
549
16th to endNight
13%13%37%29%4
576
April1st to 15thNight
15%9%43%30%1
539
16th to endNight
17%9%43%22%7%
540
May1st to 15thNight
14%8%38%32%6%
540
16th to endNight
11%433%34%15%
563
June1st to 15thNight
424%48%19%1
540
16th to endNight
6%18%50%21%2
540
July1st to 15thNight
5%14%48%28%3
510
16th to endNight
46%54%29%3
564
August1st to 15thNight
2451%37%4
527
16th to endNight
6%5%47%36%3
525
September1st to 15thNight
9%6%40%35%6%
495
16th to endNight
9%8%36%40%3
492
October1st to 15thNight
9%216%40%27%3
513
16th to endNight
10%5%25%31%25%1
704
November1st to 15thNight
12%5%27%33%18%1
709
16th to endNight
17%8%26%32%14%1
900
December1st to 15thNight
20%8%30%31%9%
900
16th to endNight
21%10%28%30%9%
960
Page generated at 2017-08-13 13:16:20. Version ac04

Copyright 2017 A. Danko


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