Petit Jean State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Petit Jean State Park clear sky chart from 2005-11-05 to 2017-12-02.

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
54%
15974
26%
48086
20%
15930
60%
15930
33%
28244

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
37%
898
29%
2327
13%
895
47%
895
34%
1430
January16th to endNight
36%
960
29%
2496
12%
960
45%
960
34%
1561
February1st to 15thNight
36%
880
21%
2288
8%
876
43%
876
30%
1490
February16th to endNight
35%
592
28%
1854
13%
592
48%
592
30%
1089
March1st to 15thNight
39%
540
22%
1980
16%
540
47%
540
21%
1210
March16th to endNight
44%
576
20%
2112
19%
576
50%
576
23%
1321
April1st to 15thNight
42%
539
25%
1812
18%
539
55%
539
32%
1011
April16th to endNight
44%
540
24%
1800
18%
540
56%
540
30%
1046
May1st to 15thNight
54%
539
20%
1719
18%
539
59%
539
27%
1062
May16th to endNight
63%
562
22%
1684
21%
561
66%
561
31%
1024
June1st to 15thNight
79%
540
25%
1554
23%
540
81%
540
48%
816
June16th to endNight
80%
540
25%
1620
26%
540
81%
540
43%
860
July1st to 15thNight
75%
510
18%
1530
20%
510
76%
510
35%
911
July16th to endNight
83%
564
24%
1594
28%
531
84%
531
43%
863
August1st to 15thNight
80%
539
24%
1634
28%
536
81%
536
41%
887
August16th to endNight
78%
573
24%
1910
30%
573
78%
573
34%
1073
September1st to 15thNight
72%
540
26%
1800
29%
540
73%
540
34%
1011
September16th to endNight
72%
582
34%
1986
34%
582
75%
582
38%
1057
October1st to 15thNight
67%
720
31%
2160
26%
720
69%
720
40%
1197
October16th to endNight
57%
768
37%
2304
27%
768
65%
768
43%
1218
November1st to 15thNight
55%
760
30%
2280
23%
760
62%
760
37%
1279
November16th to endNight
49%
842
30%
2542
21%
842
57%
842
32%
1483
December1st to 15thNight
42%
910
21%
2547
13%
910
48%
910
30%
1644
December16th to endNight
38%
960
24%
2553
12%
960
45%
960
26%
1701

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
13%5%2443445%7%45%
48286
Night
12%424323346%51%
48282
TransparencyDay
38%5%10%22%18%4
47986
Night
33%410%24%21%5%
48087
SeeingDay
12%314%26%29%13%
5954
Night
14%5%19%35%22%2
15978

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
19%5%2332323450%
1611
16th to endDay
13%6%24423335%49%
1728
February1st to 15thDay
17%6%3431223448%
1575
16th to endDay
16%8%35%423336%42%
1628
March1st to 15thDay
19%5%23324345%44%
1980
16th to endDay
18%6%25%423345%41%
2110
April1st to 15thDay
14%5%25%423447%45%
2135
16th to endDay
16%5%25%43345%6%41%
2160
May1st to 15thDay
16%6%35%6%3435%6%38%
2229
16th to endDay
10%5%26%7%36%5%6%8%36%
2430
June1st to 15thDay
6%425%6%46%5%6%9%43%
2340
16th to endDay
6%3245%36%5%7%10%44%
2340
July1st to 15thDay
7%5%36%7%46%6%7%10%34%
2340
16th to endDay
5%4235%36%6%7%10%43%
2466
August1st to 15thDay
8%315%6%36%6%6%10%40%
2314
16th to endDay
9%425%5%35%6%6%8%41%
2292
September1st to 15thDay
13%5%1443445%7%45%
2160
16th to endDay
10%324425%346%51%
1959
October1st to 15thDay
12%5%24323346%51%
1800
16th to endDay
13%31321334458%
1920
November1st to 15thDay
12%5%24323235%54%
1908
16th to endDay
16%6%23312335%50%
1743
December1st to 15thDay
18%5%1422235%6%46%
1450
16th to endDay
21%5%2442333344%
1668
January1st to 15thNight
18%413312235%53%
2327
16th to endNight
15%5%24323335%52%
2496
February1st to 15thNight
16%6%24323346%47%
2278
16th to endNight
15%414312336%52%
1854
March1st to 15thNight
18%6%2432334445%
1980
16th to endNight
17%6%24423335%44%
2112
April1st to 15thNight
11%414423347%52%
1812
16th to endNight
12%5%2442335%6%48%
1800
May1st to 15thNight
14%423425%45%8%45%
1718
16th to endNight
8%5%25%43446%9%46%
1683
June1st to 15thNight
321331345%10%59%
1554
16th to endNight
422232446%10%57%
1620
July1st to 15thNight
3325%6%35%6%8%9%45%
1620
16th to endNight
313335%5%6%12%54%
1702
August1st to 15thNight
431442446%10%52%
1644
16th to endNight
6%3144446%6%9%48%
1910
September1st to 15thNight
9%5%2442345%6%53%
1800
16th to endNight
7%31332345%6%56%
1986
October1st to 15thNight
10%313323346%56%
2160
16th to endNight
12%31221222464%
2304
November1st to 15thNight
10%423313347%55%
2280
16th to endNight
15%5%13313335%53%
2542
December1st to 15thNight
19%5%24323335%46%
2547
16th to endNight
19%6%25%32333445%
2553

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
40%27%24%19%5%
1612
16th to endDay
37%36%27%20%3
1728
February1st to 15thDay
40%39%25%16%4
1576
16th to endDay
43%48%20%18%4
1628
March1st to 15thDay
43%49%18%17%7%
1980
16th to endDay
44%5%10%24%13%1
2112
April1st to 15thDay
39%410%21%20%4
2135
16th to endDay
42%6%9%19%18%3
2160
May1st to 15thDay
46%6%8%16%18%2
2229
16th to endDay
43%8%12%21%12%1
2434
June1st to 15thDay
36%7%13%24%18%
2340
16th to endDay
32%7%14%24%17%2
2340
July1st to 15thDay
40%9%13%25%10%1
2201
16th to endDay
30%10%17%26%13%1
2311
August1st to 15thDay
35%8%14%23%15%1
2300
16th to endDay
36%9%16%19%14%4
2292
September1st to 15thDay
36%6%11%20%17%7%
2160
16th to endDay
33%5%9%21%24%5%
1959
October1st to 15thDay
34%48%21%23%7%
1800
16th to endDay
28%35%25%26%10%
1920
November1st to 15thDay
32%47%26%21%7%
1908
16th to endDay
37%37%20%26%5%
1743
December1st to 15thDay
38%412%23%17%4
1450
16th to endDay
44%48%21%16%4
1668
January1st to 15thNight
35%27%22%28%4
2327
16th to endNight
35%36%25%22%6%
2496
February1st to 15thNight
38%49%23%18%5%
2288
16th to endNight
35%38%26%18%7%
1854
March1st to 15thNight
42%49%16%20%6%
1980
16th to endNight
43%48%23%17%3
2112
April1st to 15thNight
31%410%23%21%7%
1812
16th to endNight
35%49%24%22%4
1800
May1st to 15thNight
37%6%10%21%18%5%
1719
16th to endNight
34%7%16%25%15%1
1685
June1st to 15thNight
20%6%12%33%25%2
1554
16th to endNight
22%6%13%27%23%5%
1620
July1st to 15thNight
29%8%17%24%16%2
1530
16th to endNight
20%9%17%31%18%2
1594
August1st to 15thNight
25%6%16%30%18%2
1634
16th to endNight
29%7%16%24%18%3
1910
September1st to 15thNight
31%5%9%25%20%8%
1800
16th to endNight
27%5%8%23%26%7%
1986
October1st to 15thNight
28%410%21%23%11%
2160
16th to endNight
26%35%21%32%11%
2304
November1st to 15thNight
29%48%24%22%10%
2280
16th to endNight
33%36%21%27%6%
2542
December1st to 15thNight
40%39%22%18%5%
2547
16th to endNight
43%38%22%17%5%
2553

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
28%6%21%28%13%1
90
16th to endDay
16%16%28%27%10%1
96
February1st to 15thDay
13%13%35%27%8%1
90
16th to endDay
17%12%37%24%7%1
81
March1st to 15thDay
25%11%30%27%5%
90
16th to endDay
14%17%27%21%18%
96
April1st to 15thDay
18%9%26%29%14%1
254
16th to endDay
20%5%25%28%17%4
270
May1st to 15thDay
19%421%30%19%4
366
16th to endDay
11%418%35%23%6%
517
June1st to 15thDay
7%210%24%37%17%
495
16th to endDay
5%211%29%33%17%
495
July1st to 15thDay
8%17%32%32%18%
475
16th to endDay
5%317%39%32%
515
August1st to 15thDay
10%15%23%41%18%
467
16th to endDay
14%213%45%23%
332
September1st to 15thDay
10%5%19%42%21%
315
16th to endDay
9%225%43%17%
171
October1st to 15thDay
8%314%32%31%9%
135
16th to endDay
14%417%29%21%11%
144
November1st to 15thDay
19%117%31%23%6%
135
16th to endDay
21%5%23%25%18%4
135
December1st to 15thDay
18%5%27%24%19%5%
94
16th to endDay
22%11%28%31%6%
96
January1st to 15thNight
21%9%26%34%7%
900
16th to endNight
17%6%35%35%4
960
February1st to 15thNight
19%9%29%37%4
880
16th to endNight
17%11%31%36%2
592
March1st to 15thNight
20%7%27%40%4
540
16th to endNight
17%6%25%38%10%
576
April1st to 15thNight
12%6%33%36%10%
539
16th to endNight
15%7%28%35%13%
540
May1st to 15thNight
15%318%42%18%1
540
16th to endNight
10%214%42%27%3
563
June1st to 15thNight
47%37%43%4
540
16th to endNight
5%5%32%51%4
540
July1st to 15thNight
35%33%49%6%
510
16th to endNight
3323%56%12%
564
August1st to 15thNight
5%1329%51%9%
539
16th to endNight
8%430%50%6%
573
September1st to 15thNight
11%16%26%49%5%
540
16th to endNight
9%18%32%41%5%
582
October1st to 15thNight
13%111%38%32%3
720
16th to endNight
13%419%38%23%1
768
November1st to 15thNight
11%6%20%41%17%1
760
16th to endNight
17%7%21%35%17%
842
December1st to 15thNight
22%6%24%37%7%
910
16th to endNight
21%9%23%38%6%
960
Page generated at 2017-12-03 10:16:48. Version ac04

Copyright 2017 A. Danko


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