Tunnel Ridge Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tunnel Ridge Road 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
43%
15498
19%
46984
14%
15454
49%
15454
23%
31141

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
18%
720
14%
2327
6%
716
27%
716
12%
1753
January16th to endNight
19%
768
17%
2496
8%
768
30%
768
16%
1780
February1st to 15thNight
20%
704
14%
2172
6%
701
28%
701
16%
1555
February16th to endNight
18%
631
14%
1893
6%
631
26%
631
14%
1417
March1st to 15thNight
25%
720
17%
2061
9%
720
32%
720
18%
1469
March16th to endNight
32%
768
14%
2112
8%
768
36%
768
20%
1521
April1st to 15thNight
34%
626
21%
1884
11%
626
44%
626
26%
1179
April16th to endNight
38%
540
20%
1635
11%
540
46%
540
25%
1071
May1st to 15thNight
39%
540
14%
1620
9%
540
44%
540
20%
1129
May16th to endNight
58%
562
18%
1683
15%
561
60%
561
28%
1075
June1st to 15thNight
67%
540
17%
1620
15%
540
69%
540
34%
962
June16th to endNight
66%
540
16%
1620
15%
540
67%
540
33%
983
July1st to 15thNight
64%
510
12%
1530
12%
510
64%
510
27%
988
July16th to endNight
71%
564
19%
1595
17%
531
74%
531
33%
970
August1st to 15thNight
74%
539
21%
1609
20%
536
75%
536
35%
949
August16th to endNight
75%
573
22%
1821
22%
573
75%
573
33%
1051
September1st to 15thNight
63%
696
24%
1956
20%
696
65%
696
32%
1219
September16th to endNight
61%
685
25%
1892
21%
685
63%
685
32%
1192
October1st to 15thNight
55%
660
30%
1867
26%
660
60%
660
36%
1113
October16th to endNight
41%
704
24%
2139
19%
704
49%
704
26%
1363
November1st to 15thNight
47%
700
28%
2276
24%
700
56%
700
31%
1312
November16th to endNight
34%
720
21%
2340
14%
720
44%
720
23%
1518
December1st to 15thNight
26%
720
14%
2340
10%
720
32%
720
14%
1715
December16th to endNight
24%
768
16%
2496
8%
768
34%
768
13%
1857

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%35%5%3445%7%36%
47886
Night
14%7%35%42445%7%39%
47178
Cloud CoverDay
15%7%35%5%3445%7%36%
47896
Night
14%7%35%42445%7%39%
47182
TransparencyDay
46%6%11%20%13%2
47597
Night
43%6%11%21%15%3
46985
SeeingDay
19%7%21%21%18%10%
5355
Night
18%8%23%28%18%2
15499

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
19%11%6%9%6%23345%25%
1611
16th to endDay
18%14%5%6%423335%31%
1728
February1st to 15thDay
17%12%6%9%5%24345%28%
1687
16th to endDay
17%12%5%6%5%44445%29%
1580
March1st to 15thDay
23%9%34424445%33%
1888
16th to endDay
20%8%26%5%3445%5%33%
2112
April1st to 15thDay
15%7%345%24446%39%
2073
16th to endDay
17%6%25%5%34447%37%
2325
May1st to 15thDay
20%7%36%5%35%5%46%30%
2331
16th to endDay
11%5%25%6%36%5%6%8%36%
2431
June1st to 15thDay
9%436%6%35%6%6%9%38%
2340
16th to endDay
9%5%26%6%45%6%6%9%38%
2340
July1st to 15thDay
14%5%27%6%26%5%6%9%33%
2340
16th to endDay
11%5%25%6%47%6%7%9%33%
2465
August1st to 15thDay
11%5%25%6%35%6%6%9%36%
2340
16th to endDay
9%5%246%35%6%6%10%38%
2379
September1st to 15thDay
13%6%25%435%45%8%39%
1992
16th to endDay
17%425%423447%42%
1881
October1st to 15thDay
12%5%25%423447%48%
1763
16th to endDay
21%6%13423235%45%
1730
November1st to 15thDay
14%6%1442333449%
1582
16th to endDay
16%9%35%414435%40%
1620
December1st to 15thDay
24%10%45%423345%30%
1620
16th to endDay
21%12%5%5%5%34345%28%
1728
January1st to 15thNight
19%11%5%8%5%34345%27%
2327
16th to endNight
19%11%46%5%2434432%
2496
February1st to 15thNight
17%10%5%7%5%24445%32%
2170
16th to endNight
18%12%47%5%3434429%
1893
March1st to 15thNight
18%11%346%34335%35%
2049
16th to endNight
15%9%36%5%35%45%6%34%
2112
April1st to 15thNight
14%5%25%3235%47%45%
1884
16th to endNight
14%6%25%4345%5%6%42%
1635
May1st to 15thNight
18%6%26%5%246%47%34%
1620
16th to endNight
8%425%6%35%46%9%41%
1682
June1st to 15thNight
5%324425%5%7%12%45%
1620
16th to endNight
8%223425%6%8%13%41%
1620
July1st to 15thNight
9%5%26%5%35%5%5%9%41%
1620
16th to endNight
6%423436%47%11%45%
1703
August1st to 15thNight
6%4244345%7%9%49%
1620
16th to endNight
6%3244246%7%9%48%
1821
September1st to 15thNight
12%4244245%5%9%45%
1956
16th to endNight
10%6%25%424346%48%
1892
October1st to 15thNight
11%414423347%51%
1867
16th to endNight
17%6%24323445%44%
2139
November1st to 15thNight
13%7%24312335%51%
2276
16th to endNight
19%8%23422345%41%
2340
December1st to 15thNight
21%12%47%433335%29%
2340
16th to endNight
21%12%46%424445%28%
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
19%11%6%10%6%23335%25%
1611
16th to endDay
18%14%6%6%5%24335%30%
1728
February1st to 15thDay
17%12%6%9%424345%28%
1687
16th to endDay
17%12%5%6%6%44435%29%
1580
March1st to 15thDay
23%9%3442444433%
1899
16th to endDay
20%8%26%5%3445%5%33%
2111
April1st to 15thDay
15%7%35%5%245%46%39%
2073
16th to endDay
17%5%25%5%34447%37%
2325
May1st to 15thDay
20%7%36%5%36%5%46%30%
2331
16th to endDay
11%5%25%7%46%6%6%9%36%
2431
June1st to 15thDay
9%435%5%45%5%6%9%38%
2340
16th to endDay
9%426%5%45%7%6%9%38%
2340
July1st to 15thDay
14%5%26%6%35%5%6%8%33%
2340
16th to endDay
11%5%26%5%47%6%7%9%32%
2465
August1st to 15thDay
11%5%25%6%36%6%6%10%35%
2340
16th to endDay
10%5%245%35%5%7%10%39%
2379
September1st to 15thDay
14%5%25%43445%7%39%
1992
16th to endDay
17%426%423446%42%
1881
October1st to 15thDay
12%6%25%422446%48%
1763
16th to endDay
20%7%13323235%45%
1730
November1st to 15thDay
14%6%1443333449%
1582
16th to endDay
16%9%35%424445%40%
1620
December1st to 15thDay
24%11%36%423345%30%
1620
16th to endDay
21%12%5%6%5%34345%28%
1728
January1st to 15thNight
19%11%5%8%5%34345%27%
2327
16th to endNight
18%11%46%5%2444432%
2496
February1st to 15thNight
17%10%47%42445%5%32%
2163
16th to endNight
18%13%47%5%44445%29%
1893
March1st to 15thNight
18%10%345%34345%34%
2061
16th to endNight
15%8%46%5%3445%6%35%
2112
April1st to 15thNight
14%434324447%45%
1884
16th to endNight
14%6%244345%5%6%42%
1635
May1st to 15thNight
18%6%26%5%246%47%34%
1619
16th to endNight
8%435%6%35%46%9%41%
1682
June1st to 15thNight
5%324425%6%7%12%45%
1620
16th to endNight
8%323325%6%8%13%41%
1620
July1st to 15thNight
9%5%26%5%445%5%9%41%
1620
16th to endNight
6%414435%5%6%12%44%
1703
August1st to 15thNight
6%4243345%7%9%49%
1620
16th to endNight
6%3244345%7%9%48%
1821
September1st to 15thNight
12%3245%245%49%45%
1956
16th to endNight
10%6%25%434346%49%
1892
October1st to 15thNight
11%5%14413438%51%
1867
16th to endNight
17%6%24323445%44%
2139
November1st to 15thNight
13%6%24222335%51%
2276
16th to endNight
19%8%23423345%42%
2340
December1st to 15thNight
21%12%47%433335%30%
2340
16th to endNight
22%12%46%5%24445%28%
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
60%47%16%9%
1612
16th to endDay
56%310%21%7%1
1728
February1st to 15thDay
57%48%21%7%1
1689
16th to endDay
56%410%19%7%
1580
March1st to 15thDay
53%410%18%11%2
1899
16th to endDay
51%5%10%21%9%
2112
April1st to 15thDay
43%5%9%23%14%3
2073
16th to endDay
45%410%20%13%4
2325
May1st to 15thDay
52%7%11%18%8%1
2331
16th to endDay
42%9%13%21%11%1
2435
June1st to 15thDay
39%9%12%22%14%1
2340
16th to endDay
39%9%13%16%18%2
2340
July1st to 15thDay
45%8%13%15%14%2
2201
16th to endDay
42%10%13%19%11%2
2310
August1st to 15thDay
40%10%14%20%12%1
2327
16th to endDay
38%8%15%20%14%2
2379
September1st to 15thDay
42%6%11%19%15%5%
1992
16th to endDay
41%5%9%19%22%2
1881
October1st to 15thDay
36%5%9%22%22%3
1763
16th to endDay
42%38%25%17%2
1730
November1st to 15thDay
39%47%22%21%5%
1582
16th to endDay
46%37%22%19%1
1620
December1st to 15thDay
55%49%19%8%1
1620
16th to endDay
57%411%18%6%
1728
January1st to 15thNight
60%47%14%11%1
2327
16th to endNight
55%39%21%9%1
2496
February1st to 15thNight
53%410%20%9%1
2172
16th to endNight
57%5%10%17%8%
1893
March1st to 15thNight
52%49%19%12%2
2061
16th to endNight
49%6%11%21%10%
2112
April1st to 15thNight
38%5%10%21%19%4
1884
16th to endNight
41%6%10%21%14%5%
1635
May1st to 15thNight
47%7%13%19%9%2
1620
16th to endNight
36%9%15%21%14%2
1684
June1st to 15thNight
29%9%16%25%16%2
1620
16th to endNight
31%8%17%21%16%4
1620
July1st to 15thNight
38%8%14%19%15%4
1530
16th to endNight
29%10%15%25%14%3
1595
August1st to 15thNight
29%9%17%22%19%2
1609
16th to endNight
29%8%14%24%18%3
1821
September1st to 15thNight
34%7%11%21%18%6%
1956
16th to endNight
36%5%9%19%26%2
1892
October1st to 15thNight
32%5%10%26%19%5%
1867
16th to endNight
40%5%7%22%20%3
2139
November1st to 15thNight
35%37%23%25%6%
2276
16th to endNight
45%38%23%18%1
2340
December1st to 15thNight
57%49%18%9%1
2340
16th to endNight
57%5%10%17%8%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
36%21%30%7%22
90
16th to endDay
38%26%26%8%1
96
February1st to 15thDay
27%30%32%5%4
90
16th to endDay
29%14%43%12%
81
March1st to 15thDay
34%13%30%17%2
189
16th to endDay
21%14%32%21%10%
288
April1st to 15thDay
20%13%27%24%12%1
270
16th to endDay
22%10%28%18%14%6%
270
May1st to 15thDay
27%10%24%16%12%7%
288
16th to endDay
17%5%23%23%16%13%
331
June1st to 15thDay
12%216%29%26%13%
315
16th to endDay
11%6%22%27%18%13%
315
July1st to 15thDay
21%315%26%16%16%
305
16th to endDay
12%11%25%24%25%
326
August1st to 15thDay
15%9%23%30%20%
313
16th to endDay
12%114%24%25%21%
332
September1st to 15thDay
17%212%18%31%17%
315
16th to endDay
20%211%21%28%15%
278
October1st to 15thDay
16%423%22%21%10%
255
16th to endDay
20%6%27%25%17%2
242
November1st to 15thDay
17%12%28%17%21%2
90
16th to endDay
26%12%38%16%41
90
December1st to 15thDay
24%22%34%12%6%
90
16th to endDay
29%27%35%5%3
96
January1st to 15thNight
28%17%30%18%5%
720
16th to endNight
25%16%34%21%2
768
February1st to 15thNight
26%13%34%24%1
704
16th to endNight
25%15%37%19%1
631
March1st to 15thNight
25%12%30%25%5%
720
16th to endNight
19%11%31%26%9%
768
April1st to 15thNight
17%13%32%27%9%
626
16th to endNight
17%7%32%27%14%1
540
May1st to 15thNight
21%6%25%29%14%2
540
16th to endNight
10%319%34%26%4
563
June1st to 15thNight
6%117%40%30%4
540
16th to endNight
8%117%36%33%2
540
July1st to 15thNight
12%12%35%33%4
510
16th to endNight
6%29%28%44%7%
564
August1st to 15thNight
7%18%35%39%7%
539
16th to endNight
6%8%34%41%9%
573
September1st to 15thNight
13%111%27%40%5%
696
16th to endNight
13%214%29%35%5%
685
October1st to 15thNight
15%420%28%26%5%
660
16th to endNight
20%8%25%27%16%1
704
November1st to 15thNight
17%8%22%29%19%2
700
16th to endNight
23%12%25%28%9%
720
December1st to 15thNight
29%12%25%26%5%
720
16th to endNight
29%13%28%24%3
768
Page generated at 2017-09-23 06:43:35. Version ac04

Copyright 2017 A. Danko


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