Garland Mountain Trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garland Mountain Trailhead clear sky chart from 2005-11-05 to 2017-09-20.

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
46%
15463
23%
46975
15%
15420
54%
15420
27%
29306

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
24%
720
23%
2327
9%
716
40%
716
18%
1494
January16th to endNight
24%
768
24%
2439
10%
768
39%
768
20%
1563
February1st to 15thNight
27%
704
24%
2112
10%
701
42%
701
24%
1313
February16th to endNight
20%
631
23%
1893
7%
631
34%
631
21%
1231
March1st to 15thNight
27%
720
21%
2079
10%
720
38%
720
24%
1349
March16th to endNight
37%
768
21%
2112
12%
768
43%
768
27%
1352
April1st to 15thNight
40%
608
24%
1866
14%
608
52%
608
30%
1093
April16th to endNight
46%
540
26%
1713
17%
540
56%
540
30%
996
May1st to 15thNight
50%
540
20%
1620
11%
540
58%
540
28%
1022
May16th to endNight
63%
561
20%
1682
15%
561
66%
561
32%
1023
June1st to 15thNight
71%
540
16%
1620
13%
540
73%
540
30%
1018
June16th to endNight
75%
540
17%
1620
14%
540
78%
540
34%
979
July1st to 15thNight
71%
510
14%
1530
13%
510
71%
510
27%
998
July16th to endNight
71%
564
16%
1595
14%
531
73%
531
28%
1022
August1st to 15thNight
73%
539
19%
1654
20%
536
73%
536
29%
1044
August16th to endNight
65%
573
20%
1910
21%
573
67%
573
23%
1268
September1st to 15thNight
62%
688
18%
1948
17%
688
63%
688
27%
1303
September16th to endNight
57%
677
26%
1870
19%
677
63%
677
32%
1156
October1st to 15thNight
54%
660
34%
1815
25%
660
62%
660
39%
1051
October16th to endNight
47%
704
32%
2118
24%
704
58%
704
34%
1206
November1st to 15thNight
47%
700
30%
2276
23%
700
59%
700
33%
1219
November16th to endNight
36%
720
27%
2340
17%
720
51%
720
26%
1387
December1st to 15thNight
30%
720
22%
2340
12%
720
42%
720
20%
1494
December16th to endNight
27%
768
19%
2496
13%
768
36%
768
17%
1725

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%25%5%35%5%5%7%39%
47854
Night
12%5%2442445%7%44%
47174
TransparencyDay
41%7%11%18%17%4
47555
Night
37%6%10%20%19%5%
46977
SeeingDay
17%7%19%22%20%12%
5344
Night
15%9%22%27%21%4
15465

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
18%7%345%24335%41%
1611
16th to endDay
17%6%25%423435%43%
1782
February1st to 15thDay
18%8%23424447%39%
1750
16th to endDay
19%6%25%424345%41%
1580
March1st to 15thDay
17%6%25%425%45%7%38%
1880
16th to endDay
15%5%36%5%3445%7%40%
2111
April1st to 15thDay
13%5%245%2445%7%43%
2091
16th to endDay
12%315%5%26%447%44%
2247
May1st to 15thDay
11%5%26%5%35%45%7%41%
2331
16th to endDay
8%6%26%5%36%5%6%8%40%
2431
June1st to 15thDay
9%5%25%6%47%6%8%10%33%
2340
16th to endDay
6%325%5%36%7%8%10%40%
2340
July1st to 15thDay
11%435%5%48%8%8%11%28%
2340
16th to endDay
7%437%8%48%7%7%10%29%
2465
August1st to 15thDay
8%436%6%48%7%7%10%31%
2292
16th to endDay
12%6%36%8%48%8%6%7%26%
2292
September1st to 15thDay
12%7%26%6%345%6%9%34%
1998
16th to endDay
14%5%245%3435%8%41%
1859
October1st to 15thDay
12%41432434453%
1815
16th to endDay
13%5%1332232457%
1749
November1st to 15thDay
13%424223346%53%
1582
16th to endDay
15%7%24323346%47%
1620
December1st to 15thDay
20%6%25%42445%6%38%
1620
16th to endDay
23%8%35%423335%34%
1728
January1st to 15thNight
17%6%3441345%5%41%
2327
16th to endNight
18%7%35%423345%41%
2439
February1st to 15thNight
15%6%23424336%46%
2103
16th to endNight
18%6%145%24336%42%
1893
March1st to 15thNight
13%7%245%1445%7%43%
2079
16th to endNight
12%5%35%423446%46%
2112
April1st to 15thNight
12%413335%45%7%49%
1866
16th to endNight
9%5%2432446%7%49%
1713
May1st to 15thNight
10%425%5%45%448%44%
1619
16th to endNight
7%324435%5%7%9%46%
1682
June1st to 15thNight
5%325%5%45%6%6%11%42%
1620
16th to endNight
4324436%7%7%12%44%
1620
July1st to 15thNight
7%425%5%37%6%7%12%37%
1620
16th to endNight
5%425%5%36%7%8%12%37%
1703
August1st to 15thNight
5%415%6%36%5%7%11%43%
1665
16th to endNight
10%5%36%5%35%5%7%9%36%
1910
September1st to 15thNight
9%435%5%45%5%5%9%40%
1948
16th to endNight
11%4145%235%5%7%47%
1870
October1st to 15thNight
10%41321235%6%57%
1815
16th to endNight
10%5%3432223358%
2118
November1st to 15thNight
10%413223335%56%
2276
16th to endNight
14%7%23314445%49%
2340
December1st to 15thNight
15%7%44424346%40%
2340
16th to endNight
21%8%36%423446%34%
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
44%47%16%22%4
1612
16th to endDay
43%46%19%21%5%
1782
February1st to 15thDay
43%47%19%21%3
1752
16th to endDay
45%37%19%19%4
1580
March1st to 15thDay
43%49%16%19%5%
1880
16th to endDay
43%5%11%21%15%2
2112
April1st to 15thDay
39%5%9%21%19%4
2091
16th to endDay
37%5%9%21%20%4
2247
May1st to 15thDay
40%7%11%20%17%3
2331
16th to endDay
39%9%14%20%13%3
2435
June1st to 15thDay
41%11%16%21%8%1
2340
16th to endDay
32%11%16%23%13%2
2340
July1st to 15thDay
43%10%18%16%8%1
2201
16th to endDay
44%11%16%16%9%1
2310
August1st to 15thDay
42%10%16%19%8%1
2279
16th to endDay
51%10%13%13%9%1
2292
September1st to 15thDay
43%9%11%16%14%3
1998
16th to endDay
41%5%11%16%20%4
1859
October1st to 15thDay
33%5%7%17%27%9%
1815
16th to endDay
32%26%18%30%10%
1749
November1st to 15thDay
32%25%17%32%9%
1582
16th to endDay
39%46%16%26%7%
1620
December1st to 15thDay
44%5%8%18%16%6%
1620
16th to endDay
52%39%16%15%4
1728
January1st to 15thNight
43%5%6%17%22%4
2327
16th to endNight
44%36%19%21%6%
2439
February1st to 15thNight
39%37%20%21%7%
2112
16th to endNight
43%45%20%22%3
1893
March1st to 15thNight
40%5%9%18%18%7%
2079
16th to endNight
38%5%9%25%18%3
2112
April1st to 15thNight
32%6%10%23%22%5%
1866
16th to endNight
32%5%9%24%20%7%
1713
May1st to 15thNight
37%7%13%20%19%2
1620
16th to endNight
31%9%15%24%15%2
1684
June1st to 15thNight
33%10%21%23%10%1
1620
16th to endNight
29%10%19%22%14%3
1620
July1st to 15thNight
36%10%19%20%11%1
1530
16th to endNight
33%11%21%19%11%2
1595
August1st to 15thNight
34%10%16%24%13%1
1654
16th to endNight
41%9%15%17%14%1
1910
September1st to 15thNight
39%8%14%18%14%4
1948
16th to endNight
34%6%10%24%18%5%
1870
October1st to 15thNight
28%5%10%19%27%8%
1815
16th to endNight
31%3317%30%12%
2118
November1st to 15thNight
29%35%17%30%12%
2276
16th to endNight
36%45%18%26%8%
2340
December1st to 15thNight
43%48%18%18%6%
2340
16th to endNight
50%47%16%16%4
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
25%16%40%12%5%
90
16th to endDay
21%35%33%6%3
96
February1st to 15thDay
28%26%34%8%1
90
16th to endDay
28%22%38%8%2
81
March1st to 15thDay
25%18%28%20%5%1
170
16th to endDay
19%13%29%23%13%
288
April1st to 15thDay
21%11%26%22%15%2
270
16th to endDay
16%5%24%30%19%3
270
May1st to 15thDay
17%9%28%18%16%10%
288
16th to endDay
16%5%14%29%21%12%
331
June1st to 15thDay
13%29%25%25%23%
315
16th to endDay
11%15%25%21%26%
315
July1st to 15thDay
12%110%21%26%27%
305
16th to endDay
9%16%20%34%26%
326
August1st to 15thDay
16%18%26%24%23%
313
16th to endDay
16%19%23%29%19%
332
September1st to 15thDay
15%5%13%21%26%18%
315
16th to endDay
18%315%25%27%9%
270
October1st to 15thDay
18%420%27%21%6%
255
16th to endDay
16%8%20%25%23%6%
258
November1st to 15thDay
23%18%22%24%8%2
90
16th to endDay
18%16%33%20%7%3
90
December1st to 15thDay
26%21%31%15%5%
90
16th to endDay
38%15%31%12%2
96
January1st to 15thNight
25%19%26%22%6%
720
16th to endNight
22%18%30%23%4
768
February1st to 15thNight
20%17%30%27%3
704
16th to endNight
21%20%34%20%3
631
March1st to 15thNight
18%16%34%23%6%
720
16th to endNight
17%12%28%27%13%
768
April1st to 15thNight
15%11%30%27%15%
608
16th to endNight
12%10%25%32%17%1
540
May1st to 15thNight
11%7%23%31%23%2
540
16th to endNight
11%116%31%32%6%
563
June1st to 15thNight
7%11%32%36%10%
540
16th to endNight
49%29%43%12%
540
July1st to 15thNight
8%16%25%44%14%
510
16th to endNight
6%8%26%43%14%
564
August1st to 15thNight
8%16%28%44%11%
539
16th to endNight
12%110%26%38%10%
573
September1st to 15thNight
12%111%27%36%10%
688
16th to endNight
14%219%31%29%2
677
October1st to 15thNight
13%5%23%30%21%5%
660
16th to endNight
11%10%25%27%21%3
704
November1st to 15thNight
13%10%24%28%20%2
700
16th to endNight
19%15%25%25%12%
720
December1st to 15thNight
21%15%27%24%10%1
720
16th to endNight
27%14%26%24%6%
768
Page generated at 2017-09-21 07:18:24. Version ac04

Copyright 2017 A. Danko


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