Natural Tunnel State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Natural Tunnel State Park clear sky chart from 2005-11-05 to 2017-09-22.

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
49%
15597
20%
46974
16%
15554
54%
15554
25%
30422

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
30%
720
18%
2327
13%
716
39%
716
17%
1639
January16th to endNight
30%
768
20%
2496
12%
768
40%
768
18%
1673
February1st to 15thNight
29%
704
17%
2192
9%
701
38%
701
20%
1480
February16th to endNight
25%
631
20%
1893
11%
631
33%
631
17%
1334
March1st to 15thNight
35%
720
21%
2025
13%
720
41%
720
22%
1393
March16th to endNight
41%
768
16%
2112
11%
768
45%
768
25%
1450
April1st to 15thNight
42%
688
22%
1939
13%
688
50%
688
29%
1197
April16th to endNight
48%
540
22%
1620
13%
540
56%
540
26%
1047
May1st to 15thNight
48%
539
15%
1620
10%
539
53%
539
24%
1079
May16th to endNight
62%
561
16%
1683
11%
561
64%
561
28%
1088
June1st to 15thNight
68%
540
14%
1620
11%
540
70%
540
30%
1007
June16th to endNight
67%
540
17%
1620
15%
540
68%
540
29%
1014
July1st to 15thNight
64%
510
11%
1530
11%
510
64%
510
26%
996
July16th to endNight
73%
564
16%
1595
15%
531
76%
531
30%
981
August1st to 15thNight
71%
539
18%
1609
17%
536
71%
536
30%
1012
August16th to endNight
71%
588
22%
1801
20%
588
73%
588
30%
1101
September1st to 15thNight
61%
720
21%
1980
18%
720
62%
720
28%
1292
September16th to endNight
59%
685
26%
1892
22%
685
61%
685
32%
1179
October1st to 15thNight
58%
660
32%
1889
30%
660
62%
660
36%
1137
October16th to endNight
49%
704
29%
2112
24%
704
57%
704
31%
1266
November1st to 15thNight
53%
700
29%
2243
28%
700
60%
700
33%
1271
November16th to endNight
46%
720
25%
2340
20%
720
54%
720
26%
1424
December1st to 15thNight
37%
720
18%
2340
15%
720
42%
720
18%
1588
December16th to endNight
31%
768
19%
2496
12%
768
40%
768
15%
1774

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%36%5%35%5%5%7%35%
47905
Night
13%6%35%5%2445%7%39%
47172
TransparencyDay
46%411%21%14%2
47606
Night
43%411%22%15%3
46975
SeeingDay
18%6%15%23%22%12%
5451
Night
17%6%17%34%20%2
15600

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%10%410%6%23445%28%
1611
16th to endDay
17%9%45%5%2435%5%36%
1728
February1st to 15thDay
18%10%37%6%24436%32%
1669
16th to endDay
18%8%47%43445%7%30%
1580
March1st to 15thDay
20%9%25%423345%37%
1935
16th to endDay
17%8%47%434446%34%
2111
April1st to 15thDay
13%5%25%4335%5%8%41%
2017
16th to endDay
16%5%25%5%3435%7%38%
2340
May1st to 15thDay
15%7%46%5%45%5%5%7%30%
2331
16th to endDay
12%6%36%6%45%45%8%35%
2431
June1st to 15thDay
8%5%36%6%5%5%6%8%10%33%
2340
16th to endDay
9%5%35%6%36%6%7%9%34%
2340
July1st to 15thDay
12%5%26%6%46%6%7%10%30%
2340
16th to endDay
11%6%26%7%47%7%7%10%28%
2465
August1st to 15thDay
11%5%36%7%46%7%7%10%28%
2340
16th to endDay
9%6%25%7%46%7%7%9%33%
2385
September1st to 15thDay
12%6%35%6%35%5%6%7%38%
1980
16th to endDay
15%6%245%3345%6%42%
1881
October1st to 15thDay
13%423323446%50%
1741
16th to endDay
17%7%24424336%44%
1760
November1st to 15thDay
12%6%1432345%6%48%
1612
16th to endDay
15%7%25%433346%42%
1620
December1st to 15thDay
20%9%36%324437%34%
1620
16th to endDay
22%10%36%43335%6%30%
1728
January1st to 15thNight
17%6%5%8%6%34445%32%
2327
16th to endNight
17%8%36%6%24445%35%
2496
February1st to 15thNight
15%8%37%6%3445%6%34%
2183
16th to endNight
16%9%5%7%5%2445%7%30%
1893
March1st to 15thNight
16%9%35%5%34445%37%
2025
16th to endNight
13%7%37%5%35%447%37%
2112
April1st to 15thNight
12%6%344235%6%8%43%
1939
16th to endNight
11%6%36%435%5%5%6%41%
1620
May1st to 15thNight
16%6%25%425%5%6%9%36%
1619
16th to endNight
7%6%25%6%35%6%8%9%37%
1682
June1st to 15thNight
8%5%345%245%8%11%39%
1620
16th to endNight
9%4245%35%47%11%40%
1620
July1st to 15thNight
11%5%35%6%35%5%6%9%38%
1620
16th to endNight
7%3245%38%5%8%11%39%
1703
August1st to 15thNight
7%425%5%35%6%6%10%41%
1620
16th to endNight
9%4145%35%6%7%9%41%
1801
September1st to 15thNight
12%6%26%5%2445%8%41%
1980
16th to endNight
13%5%15%433445%48%
1892
October1st to 15thNight
13%5%14314335%52%
1889
16th to endNight
13%5%25%423236%49%
2112
November1st to 15thNight
12%5%24322246%52%
2243
16th to endNight
15%5%34324347%44%
2340
December1st to 15thNight
18%8%46%5%245%5%6%33%
2340
16th to endNight
20%11%37%5%24345%30%
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
57%37%17%12%1
1612
16th to endDay
48%210%26%11%1
1728
February1st to 15thDay
53%37%21%13%1
1671
16th to endDay
53%210%20%11%1
1580
March1st to 15thDay
48%28%21%15%3
1935
16th to endDay
51%49%21%11%1
2112
April1st to 15thDay
39%312%24%16%3
2017
16th to endDay
45%38%24%14%4
2340
May1st to 15thDay
51%413%17%10%2
2331
16th to endDay
45%412%24%9%2
2435
June1st to 15thDay
41%6%17%22%10%1
2340
16th to endDay
41%7%13%17%16%2
2340
July1st to 15thDay
46%6%15%15%13%2
2201
16th to endDay
46%6%15%18%11%2
2310
August1st to 15thDay
47%6%14%18%11%1
2327
16th to endDay
42%5%14%20%14%2
2385
September1st to 15thDay
42%5%11%21%15%4
1980
16th to endDay
41%39%20%22%2
1881
October1st to 15thDay
35%38%25%21%5%
1741
16th to endDay
42%26%24%18%5%
1760
November1st to 15thDay
35%25%21%28%5%
1612
16th to endDay
42%25%24%21%2
1620
December1st to 15thDay
50%39%21%12%2
1620
16th to endDay
54%211%18%11%1
1728
January1st to 15thNight
54%28%17%14%3
2327
16th to endNight
49%28%22%14%1
2496
February1st to 15thNight
50%18%24%12%1
2192
16th to endNight
52%39%23%9%2
1893
March1st to 15thNight
49%28%22%14%2
2025
16th to endNight
46%311%24%12%1
2112
April1st to 15thNight
37%310%26%17%4
1939
16th to endNight
42%411%20%14%5%
1620
May1st to 15thNight
43%6%16%21%10%1
1620
16th to endNight
38%7%16%23%10%3
1684
June1st to 15thNight
35%7%20%21%12%2
1620
16th to endNight
35%8%14%22%14%4
1620
July1st to 15thNight
40%6%16%18%13%2
1530
16th to endNight
33%8%19%21%14%2
1595
August1st to 15thNight
35%7%18%21%15%1
1609
16th to endNight
36%5%14%27%13%1
1801
September1st to 15thNight
39%6%12%20%16%4
1980
16th to endNight
37%310%21%24%2
1892
October1st to 15thNight
34%37%25%23%5%
1889
16th to endNight
38%15%25%22%6%
2112
November1st to 15thNight
34%16%21%27%8%
2243
16th to endNight
40%26%24%22%2
2340
December1st to 15thNight
51%29%20%12%3
2340
16th to endNight
56%29%16%13%1
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
31%13%31%18%32
90
16th to endDay
27%26%27%12%7%
96
February1st to 15thDay
25%22%40%10%2
90
16th to endDay
25%16%32%23%2
81
March1st to 15thDay
24%9%23%33%7%
225
16th to endDay
19%9%26%29%15%1
288
April1st to 15thDay
17%11%17%30%18%4
270
16th to endDay
21%5%18%25%23%5%
270
May1st to 15thDay
22%10%21%21%14%9%
288
16th to endDay
16%416%19%23%19%
331
June1st to 15thDay
9%411%26%29%19%
315
16th to endDay
12%5%16%20%27%17%
315
July1st to 15thDay
18%115%24%22%17%
305
16th to endDay
12%1422%35%23%
326
August1st to 15thDay
15%16%24%28%23%
313
16th to endDay
13%26%20%31%25%
332
September1st to 15thDay
15%37%19%33%20%
315
16th to endDay
21%18%23%28%16%
278
October1st to 15thDay
20%5%13%21%31%7%
255
16th to endDay
20%6%14%26%23%7%
272
November1st to 15thDay
16%9%18%22%24%9%
120
16th to endDay
20%6%23%27%22%
90
December1st to 15thDay
22%18%23%31%4
90
16th to endDay
32%18%22%20%5%
96
January1st to 15thNight
22%11%25%34%5%
720
16th to endNight
22%11%29%33%2
768
February1st to 15thNight
23%11%27%35%1
704
16th to endNight
25%12%30%28%3
631
March1st to 15thNight
21%10%23%36%7%
720
16th to endNight
18%7%23%36%12%
768
April1st to 15thNight
17%11%23%35%11%
688
16th to endNight
15%6%21%40%16%
540
May1st to 15thNight
18%7%18%35%18%2
540
16th to endNight
13%210%34%34%4
563
June1st to 15thNight
10%37%36%35%7%
540
16th to endNight
9%36%32%42%5%
540
July1st to 15thNight
14%6%31%43%3
510
16th to endNight
8%3330%42%11%
564
August1st to 15thNight
10%330%48%5%
539
16th to endNight
12%1430%42%9%
588
September1st to 15thNight
15%35%27%42%6%
720
16th to endNight
17%210%32%32%4
685
October1st to 15thNight
16%5%16%31%25%4
660
16th to endNight
16%7%18%35%20%1
704
November1st to 15thNight
15%6%18%36%20%3
700
16th to endNight
18%10%20%38%11%
720
December1st to 15thNight
23%8%22%35%9%
720
16th to endNight
26%9%23%33%7%
768
Page generated at 2017-09-23 06:43:40. Version ac04

Copyright 2017 A. Danko


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