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 2017-09-10.

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%
15372
19%
46506
13%
15330
47%
15330
24%
30395

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
15%
720
14%
2327
6%
716
24%
716
10%
1759
January16th to endNight
19%
768
15%
2496
7%
768
29%
768
13%
1818
February1st to 15thNight
19%
702
13%
2163
5%
701
26%
701
15%
1549
February16th to endNight
18%
631
14%
1893
6%
631
26%
631
15%
1375
March1st to 15thNight
23%
720
16%
2088
9%
720
29%
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
42%
540
21%
1120
May16th to endNight
55%
562
19%
1684
14%
561
59%
561
31%
1034
June1st to 15thNight
63%
540
20%
1593
16%
540
68%
540
40%
893
June16th to endNight
62%
540
19%
1440
14%
540
67%
540
40%
868
July1st to 15thNight
60%
510
18%
1385
14%
510
63%
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
66%
646
28%
1871
23%
646
70%
646
39%
1066
September16th to endNight
57%
657
28%
1815
21%
657
61%
657
34%
1109
October1st to 15thNight
52%
660
30%
1853
23%
660
59%
660
36%
1080
October16th to endNight
37%
704
24%
2186
17%
704
46%
704
25%
1386
November1st to 15thNight
42%
700
28%
2276
22%
700
53%
700
30%
1313
November16th to endNight
31%
720
19%
2340
13%
720
39%
720
18%
1570
December1st to 15thNight
22%
720
12%
2340
7%
720
27%
720
13%
1730
December16th to endNight
19%
768
14%
2496
6%
768
28%
768
12%
1891

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%
48113
Night
14%7%35%43445%7%39%
46691
Cloud CoverDay
15%7%35%5%3445%7%37%
48123
Night
14%7%35%42445%7%39%
46695
TransparencyDay
45%411%22%14%2
47816
Night
44%311%22%15%2
46506
SeeingDay
18%8%24%23%15%9%
5581
Night
19%9%23%27%16%2
15375

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%6%2433426%
1611
16th to endDay
18%12%49%5%33345%29%
1728
February1st to 15thDay
17%13%47%5%2344432%
1696
16th to endDay
16%13%49%6%2435%5%29%
1580
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%4145%345%6%6%45%
1965
16th to endDay
15%5%25%433445%45%
1815
October1st to 15thDay
13%4145%23447%47%
1777
16th to endDay
21%6%24413336%42%
1685
November1st to 15thDay
10%7%35%424345%49%
1582
16th to endDay
17%10%46%423345%37%
1620
December1st to 15thDay
25%11%5%7%5%3343426%
1620
16th to endDay
22%14%5%6%5%23335%26%
1728
January1st to 15thNight
19%11%5%9%7%34435%25%
2327
16th to endNight
18%13%5%7%424245%29%
2496
February1st to 15thNight
20%11%47%423335%30%
2161
16th to endNight
19%12%37%423445%29%
1893
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%42222346%7%52%
1871
16th to endNight
12%415%324445%49%
1815
October1st to 15thNight
9%3144345%5%7%49%
1853
16th to endNight
17%6%34424345%43%
2186
November1st to 15thNight
14%42432345%5%48%
2276
16th to endNight
19%8%25%5%2444436%
2340
December1st to 15thNight
23%11%47%5%33345%26%
2340
16th to endNight
24%14%46%5%23345%25%
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
21%11%5%9%6%2333327%
1611
16th to endDay
17%13%5%9%5%33335%29%
1728
February1st to 15thDay
17%13%47%5%2334432%
1696
16th to endDay
16%13%48%6%24446%29%
1580
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%4145%25%46%6%45%
1965
16th to endDay
15%5%24423445%45%
1815
October1st to 15thDay
13%424423347%47%
1777
16th to endDay
21%7%24413336%42%
1685
November1st to 15thDay
10%7%34424345%49%
1582
16th to endDay
17%10%46%423435%38%
1620
December1st to 15thDay
24%11%5%6%5%3433426%
1620
16th to endDay
22%13%5%6%5%23336%26%
1728
January1st to 15thNight
19%11%5%9%6%34435%25%
2327
16th to endNight
19%13%5%7%434335%29%
2496
February1st to 15thNight
20%11%5%6%423345%30%
2154
16th to endNight
19%12%38%42445%5%29%
1893
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%42322346%7%52%
1871
16th to endNight
12%42442445%5%49%
1815
October1st to 15thNight
9%3145%245%5%7%49%
1853
16th to endNight
16%6%24424335%43%
2186
November1st to 15thNight
14%5%2432335%5%49%
2276
16th to endNight
19%9%25%5%2444436%
2340
December1st to 15thNight
23%11%47%5%23345%26%
2340
16th to endNight
23%14%47%433335%25%
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
61%28%16%10%
1612
16th to endDay
57%211%21%6%
1728
February1st to 15thDay
55%29%22%9%
1698
16th to endDay
56%210%22%7%
1580
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
37%311%20%21%5%
1965
16th to endDay
40%38%21%24%1
1815
October1st to 15thDay
36%37%27%20%3
1777
16th to endDay
43%210%27%14%2
1685
November1st to 15thDay
36%37%26%20%5%
1582
16th to endDay
48%37%23%16%
1620
December1st to 15thDay
61%29%16%8%1
1620
16th to endDay
60%310%16%8%
1728
January1st to 15thNight
61%37%16%9%
2327
16th to endNight
57%39%21%7%1
2496
February1st to 15thNight
55%211%21%7%1
2163
16th to endNight
55%311%20%9%
1893
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
29%411%25%22%6%
1871
16th to endNight
35%36%22%28%2
1815
October1st to 15thNight
31%49%29%20%4
1853
16th to endNight
43%27%27%16%2
2186
November1st to 15thNight
35%38%22%25%5%
2276
16th to endNight
50%29%22%13%1
2340
December1st to 15thNight
60%210%17%8%
2340
16th to endNight
62%39%16%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
36%16%34%10%11
90
16th to endDay
27%29%35%6%2
96
February1st to 15thDay
27%34%32%32
90
16th to endDay
23%12%50%13%
81
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
14%313%26%27%14%
294
16th to endDay
19%316%17%30%12%
254
October1st to 15thDay
14%7%25%26%17%9%
255
16th to endDay
19%7%34%27%10%
197
November1st to 15thDay
15%10%25%25%16%6%
90
16th to endDay
30%13%35%15%41
90
December1st to 15thDay
26%20%31%13%8%
90
16th to endDay
33%23%36%5%1
96
January1st to 15thNight
26%17%33%17%4
720
16th to endNight
28%17%28%23%1
768
February1st to 15thNight
29%14%31%22%1
704
16th to endNight
27%16%32%21%1
631
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
12%410%31%35%5%
646
16th to endNight
14%415%26%31%5%
657
October1st to 15thNight
12%6%23%30%22%4
660
16th to endNight
20%9%27%27%13%1
704
November1st to 15thNight
17%10%26%24%19%2
700
16th to endNight
26%14%23%26%8%
720
December1st to 15thNight
31%14%24%20%8%
720
16th to endNight
31%14%29%20%3
768
Page generated at 2017-09-11 19:35:19. Version ac04

Copyright 2017 A. Danko


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