A. J. Jolly Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the A. J. Jolly Park clear sky chart from 2005-11-05 to 2018-02-22.

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
40%
16032
19%
48558
13%
15990
47%
15990
24%
31754

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
17%
780
14%
2522
7%
776
25%
776
11%
1905
January16th to endNight
19%
832
15%
2704
7%
832
29%
832
13%
1960
February1st to 15thNight
18%
762
13%
2347
5%
761
26%
761
15%
1695
February16th to endNight
17%
659
14%
1977
5%
659
25%
659
15%
1449
March1st to 15thNight
23%
720
16%
2088
9%
720
30%
720
17%
1473
March16th to endNight
28%
768
15%
2112
7%
768
35%
768
20%
1488
April1st to 15thNight
32%
580
19%
1838
12%
580
42%
580
23%
1174
April16th to endNight
37%
540
22%
1647
12%
540
48%
540
26%
1061
May1st to 15thNight
37%
540
16%
1620
9%
540
43%
540
21%
1120
May16th to endNight
56%
562
19%
1684
14%
561
59%
561
31%
1034
June1st to 15thNight
63%
540
19%
1593
16%
540
68%
540
40%
893
June16th to endNight
62%
540
19%
1440
13%
540
66%
540
40%
868
July1st to 15thNight
59%
510
18%
1385
14%
510
62%
510
34%
869
July16th to endNight
73%
564
20%
1595
17%
531
75%
531
39%
901
August1st to 15thNight
70%
539
23%
1609
20%
536
72%
536
37%
932
August16th to endNight
75%
573
26%
1839
25%
573
77%
573
42%
936
September1st to 15thNight
65%
666
27%
1926
23%
666
68%
666
38%
1110
September16th to endNight
58%
717
31%
1980
23%
717
62%
717
36%
1181
October1st to 15thNight
53%
720
29%
2022
22%
720
59%
720
36%
1186
October16th to endNight
37%
768
25%
2385
19%
768
47%
768
26%
1500
November1st to 15thNight
41%
760
27%
2471
21%
760
52%
760
28%
1460
November16th to endNight
32%
780
21%
2535
15%
780
41%
780
19%
1667
December1st to 15thNight
23%
780
12%
2535
7%
780
29%
780
14%
1838
December16th to endNight
18%
832
13%
2704
6%
832
27%
832
12%
2054

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
15%7%36%5%3445%7%37%
49686
Night
14%7%35%5%3445%7%39%
48743
Cloud CoverDay
15%7%35%5%3445%7%37%
49696
Night
14%7%35%42445%7%39%
48747
TransparencyDay
45%411%22%14%2
49389
Night
44%311%22%15%2
48558
SeeingDay
19%9%24%22%15%8%
6119
Night
19%9%24%27%16%2
16035

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
21%11%5%9%7%3433427%
1746
16th to endDay
17%12%49%5%33345%30%
1872
February1st to 15thDay
19%12%47%5%23345%31%
1842
16th to endDay
17%13%48%5%24345%28%
1643
March1st to 15thDay
23%10%35%42344432%
1861
16th to endDay
20%10%36%6%33345%32%
2112
April1st to 15thDay
19%7%25%423446%39%
2121
16th to endDay
17%7%25%42445%7%38%
2313
May1st to 15thDay
23%6%35%4345%46%30%
2331
16th to endDay
10%5%36%6%46%6%6%8%35%
2431
June1st to 15thDay
11%4245%36%6%6%9%40%
2361
16th to endDay
9%4246%46%6%6%9%38%
2520
July1st to 15thDay
13%6%26%5%35%5%6%8%35%
2490
16th to endDay
8%4246%47%7%7%9%38%
2465
August1st to 15thDay
7%425%6%35%5%6%10%42%
2340
16th to endDay
6%5%26%5%346%7%9%43%
2361
September1st to 15thDay
12%4245%345%6%6%44%
2022
16th to endDay
14%5%25%433446%47%
1980
October1st to 15thDay
14%4145%23447%46%
1938
16th to endDay
20%6%24413336%42%
1838
November1st to 15thDay
11%8%35%42434447%
1717
16th to endDay
16%9%35%423346%38%
1755
December1st to 15thDay
23%10%47%5%43435%27%
1755
16th to endDay
22%14%5%6%5%23335%26%
1872
January1st to 15thNight
19%11%5%9%7%34435%25%
2522
16th to endNight
18%13%5%6%5%24345%30%
2704
February1st to 15thNight
21%11%47%423335%30%
2345
16th to endNight
19%12%37%42445%5%29%
1977
March1st to 15thNight
18%10%46%433447%32%
2076
16th to endNight
16%8%35%5%35%5%5%6%34%
2112
April1st to 15thNight
14%8%35%42445%7%39%
1838
16th to endNight
14%5%35%43445%7%40%
1647
May1st to 15thNight
17%6%35%5%3445%7%35%
1620
16th to endNight
9%3245%445%8%9%41%
1682
June1st to 15thNight
5%3236%344411%51%
1593
16th to endNight
5%224435%5%6%12%46%
1440
July1st to 15thNight
9%5%25%5%2436%8%46%
1467
16th to endNight
6%314425%5%6%9%49%
1703
August1st to 15thNight
6%3244345%7%9%48%
1620
16th to endNight
5%3134245%6%8%55%
1839
September1st to 15thNight
11%42322345%7%51%
1926
16th to endNight
11%415%324446%51%
1980
October1st to 15thNight
9%4144345%5%7%49%
2022
16th to endNight
16%6%24424345%43%
2385
November1st to 15thNight
14%5%2442345%5%47%
2471
16th to endNight
19%8%25%5%24445%37%
2535
December1st to 15thNight
21%11%47%5%33345%28%
2535
16th to endNight
23%14%47%5%23345%24%
2704

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
21%11%5%9%6%3333427%
1746
16th to endDay
17%13%48%5%23345%30%
1872
February1st to 15thDay
18%12%47%5%23345%31%
1842
16th to endDay
17%13%48%6%24446%29%
1643
March1st to 15thDay
23%10%35%42244432%
1872
16th to endDay
20%10%35%6%23345%32%
2111
April1st to 15thDay
19%7%25%413446%39%
2121
16th to endDay
16%7%245%2345%7%38%
2313
May1st to 15thDay
23%7%26%4345%5%6%30%
2331
16th to endDay
10%6%26%6%36%6%6%8%35%
2431
June1st to 15thDay
11%325%5%36%5%6%8%40%
2361
16th to endDay
9%5%25%5%46%6%5%9%38%
2520
July1st to 15thDay
13%6%35%5%36%5%6%8%35%
2490
16th to endDay
8%4245%47%6%6%9%38%
2465
August1st to 15thDay
7%425%6%36%5%5%10%41%
2340
16th to endDay
6%425%5%346%7%9%43%
2361
September1st to 15thDay
12%4245%25%46%6%44%
2022
16th to endDay
14%5%24423445%47%
1980
October1st to 15thDay
14%4145%23447%46%
1938
16th to endDay
20%6%24413337%42%
1838
November1st to 15thDay
11%8%34424345%47%
1717
16th to endDay
16%9%35%323446%38%
1755
December1st to 15thDay
23%10%5%7%5%3433427%
1755
16th to endDay
22%13%5%6%5%23335%26%
1872
January1st to 15thNight
19%11%5%9%7%34435%25%
2522
16th to endNight
18%13%5%7%434335%30%
2704
February1st to 15thNight
21%11%5%6%423345%30%
2338
16th to endNight
20%12%38%42445%5%29%
1977
March1st to 15thNight
18%10%46%433446%32%
2088
16th to endNight
16%9%35%5%3445%6%34%
2112
April1st to 15thNight
14%7%35%42445%6%39%
1838
16th to endNight
14%6%35%43345%7%40%
1647
May1st to 15thNight
17%6%35%5%3445%8%35%
1619
16th to endNight
9%3145%45%5%8%9%41%
1682
June1st to 15thNight
5%3235%343410%51%
1593
16th to endNight
5%3145%346%6%12%46%
1440
July1st to 15thNight
10%5%25%5%2446%8%46%
1467
16th to endNight
6%314425%6%5%9%49%
1703
August1st to 15thNight
6%315%43447%9%47%
1620
16th to endNight
5%2134235%5%9%55%
1839
September1st to 15thNight
11%42322345%7%51%
1926
16th to endNight
11%32442345%6%51%
1980
October1st to 15thNight
8%4145%345%5%7%49%
2022
16th to endNight
16%6%24424345%43%
2385
November1st to 15thNight
14%5%2432345%5%47%
2471
16th to endNight
18%9%25%5%2434438%
2535
December1st to 15thNight
22%11%47%5%23345%28%
2535
16th to endNight
23%14%47%433345%24%
2704

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
61%27%16%11%
1747
16th to endDay
56%211%22%7%
1872
February1st to 15thDay
56%29%21%8%
1844
16th to endDay
56%210%21%7%
1643
March1st to 15thDay
54%311%20%9%1
1872
16th to endDay
53%311%21%9%
2112
April1st to 15thDay
45%39%24%14%2
2121
16th to endDay
43%310%23%14%4
2313
May1st to 15thDay
52%412%18%10%1
2331
16th to endDay
42%6%14%22%12%1
2435
June1st to 15thDay
37%5%13%23%17%1
2361
16th to endDay
39%6%12%21%16%2
2520
July1st to 15thDay
44%5%11%19%17%2
2343
16th to endDay
38%7%13%24%13%2
2310
August1st to 15thDay
35%5%14%24%16%2
2327
16th to endDay
34%5%13%24%17%4
2361
September1st to 15thDay
38%310%20%20%5%
2022
16th to endDay
38%38%23%23%1
1980
October1st to 15thDay
37%38%27%19%3
1938
16th to endDay
42%210%27%14%1
1838
November1st to 15thDay
39%36%26%19%4
1717
16th to endDay
46%37%25%16%
1755
December1st to 15thDay
60%29%16%9%
1755
16th to endDay
60%310%16%8%
1872
January1st to 15thNight
61%36%16%10%
2522
16th to endNight
56%29%22%7%1
2704
February1st to 15thNight
56%211%20%7%1
2347
16th to endNight
56%310%20%8%
1977
March1st to 15thNight
52%39%21%11%1
2088
16th to endNight
48%412%22%9%
2112
April1st to 15thNight
42%49%22%18%2
1838
16th to endNight
43%210%22%13%7%
1647
May1st to 15thNight
47%5%12%22%9%2
1620
16th to endNight
34%7%16%21%16%3
1684
June1st to 15thNight
28%5%14%29%18%3
1593
16th to endNight
29%5%18%22%19%3
1440
July1st to 15thNight
36%411%23%18%5%
1385
16th to endNight
28%5%16%29%17%2
1595
August1st to 15thNight
29%6%16%24%19%3
1609
16th to endNight
24%415%29%21%4
1839
September1st to 15thNight
30%411%24%22%6%
1926
16th to endNight
33%37%24%29%2
1980
October1st to 15thNight
31%410%28%20%4
2022
16th to endNight
42%27%26%18%2
2385
November1st to 15thNight
37%38%22%23%4
2471
16th to endNight
48%29%23%14%1
2535
December1st to 15thNight
58%210%18%9%
2535
16th to endNight
62%310%16%7%
2704

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%18%33%14%2
135
16th to endDay
27%21%40%8%1
144
February1st to 15thDay
31%29%31%5%2
135
16th to endDay
30%13%45%12%
100
March1st to 15thDay
33%17%32%16%
162
16th to endDay
26%15%32%16%8%
288
April1st to 15thDay
23%14%28%20%11%1
270
16th to endDay
20%12%30%17%13%5%
270
May1st to 15thDay
28%11%29%14%10%6%
288
16th to endDay
16%8%25%24%12%12%
331
June1st to 15thDay
11%5%19%35%17%10%
336
16th to endDay
13%7%25%31%15%7%
495
July1st to 15thDay
17%319%28%19%10%
447
16th to endDay
10%112%30%21%23%
326
August1st to 15thDay
14%12%26%25%20%
313
16th to endDay
8%213%30%29%16%
332
September1st to 15thDay
16%313%24%26%14%
315
16th to endDay
16%316%17%30%15%
314
October1st to 15thDay
16%6%23%26%18%9%
315
16th to endDay
18%7%35%24%12%1
254
November1st to 15thDay
22%10%28%21%12%4
135
16th to endDay
24%12%38%18%41
135
December1st to 15thDay
23%20%33%11%10%
135
16th to endDay
34%22%38%4
144
January1st to 15thNight
26%17%33%18%4
780
16th to endNight
28%17%29%23%1
832
February1st to 15thNight
30%14%31%22%1
764
16th to endNight
28%16%32%21%1
659
March1st to 15thNight
25%16%29%23%4
720
16th to endNight
20%13%31%25%9%
768
April1st to 15thNight
19%13%30%27%8%
580
16th to endNight
17%9%30%28%12%1
540
May1st to 15thNight
20%7%27%28%14%1
540
16th to endNight
10%320%34%24%5%
563
June1st to 15thNight
7%218%42%25%2
540
16th to endNight
6%220%40%26%2
540
July1st to 15thNight
12%214%33%32%4
510
16th to endNight
7%9%35%40%6%
564
August1st to 15thNight
7%29%34%40%5%
539
16th to endNight
5%111%33%40%8%
573
September1st to 15thNight
13%410%31%34%5%
666
16th to endNight
13%415%25%34%6%
717
October1st to 15thNight
12%6%22%29%24%4
720
16th to endNight
20%9%27%26%14%1
768
November1st to 15thNight
18%9%26%24%18%2
760
16th to endNight
25%13%24%26%9%
780
December1st to 15thNight
30%15%23%22%8%
780
16th to endNight
30%14%30%20%3
832
Page generated at 2018-02-23 11:21:28. Version ac04

Copyright 2018 A. Danko


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