West Grand High School
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Grand High School clear sky chart from 2005-11-05 to 2017-09-17.

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
53%
15947
21%
46881
16%
15907
57%
15907
32%
28569

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
40%
892
15%
2500
12%
889
43%
889
23%
1743
January16th to endNight
42%
768
20%
2496
16%
768
48%
768
24%
1601
February1st to 15thNight
37%
699
11%
2288
9%
699
41%
699
20%
1581
February16th to endNight
35%
632
19%
1902
11%
632
44%
632
23%
1281
March1st to 15thNight
46%
720
21%
2058
13%
720
53%
720
33%
1255
March16th to endNight
46%
716
21%
2060
12%
716
53%
716
31%
1291
April1st to 15thNight
43%
539
18%
1798
14%
539
50%
539
27%
1070
April16th to endNight
45%
540
20%
1800
17%
540
52%
540
26%
1125
May1st to 15thNight
50%
540
18%
1584
14%
540
55%
540
26%
1048
May16th to endNight
58%
562
19%
1498
13%
561
63%
561
35%
910
June1st to 15thNight
67%
540
25%
1440
17%
540
72%
540
55%
730
June16th to endNight
75%
540
30%
1440
25%
540
77%
540
60%
695
July1st to 15thNight
82%
510
18%
1360
16%
510
82%
510
44%
763
July16th to endNight
81%
564
19%
1497
18%
531
82%
531
42%
829
August1st to 15thNight
76%
539
19%
1616
19%
536
77%
536
39%
875
August16th to endNight
79%
573
27%
1910
31%
573
80%
573
36%
1049
September1st to 15thNight
76%
540
28%
1800
30%
540
80%
540
40%
925
September16th to endNight
74%
547
33%
1807
33%
547
77%
547
48%
871
October1st to 15thNight
56%
660
26%
1980
20%
660
60%
660
36%
1155
October16th to endNight
56%
704
29%
2112
20%
704
62%
704
39%
1165
November1st to 15thNight
48%
862
25%
2262
15%
862
52%
862
38%
1370
November16th to endNight
47%
900
24%
2465
15%
900
52%
900
39%
1453
December1st to 15thNight
35%
900
11%
2520
6%
900
39%
900
22%
1782
December16th to endNight
33%
960
13%
2688
9%
960
36%
960
18%
2002

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
36%36%5%35%5%6%8%45%
47906
Night
26%36%5%2445%7%51%
47060
TransparencyDay
36%8%13%21%15%4
47587
Night
33%7%14%24%15%4
46881
SeeingDay
8%14%28%27%17%3
5841
Night
5%7%25%39%20%1
15955

By Month

Percentage Cloud Cover SW (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
8%5%9%7%46%6%6%9%34%
1447
16th to endDay
19%6%10%6%35%448%38%
1728
February1st to 15thDay
110%6%10%7%35%6%6%6%35%
1575
16th to endDay
7%5%8%7%47%6%7%7%36%
1572
March1st to 15thDay
18%5%6%6%35%45%6%46%
1899
16th to endDay
210%47%5%345%6%8%41%
2163
April1st to 15thDay
310%36%5%35%46%8%41%
2150
16th to endDay
310%46%6%46%6%7%8%35%
2160
May1st to 15thDay
6%8%25%7%45%5%7%8%37%
2364
16th to endDay
5%5%26%6%46%6%6%9%40%
2616
June1st to 15thDay
32134345%6%9%54%
2520
16th to endDay
211232345%7%65%
2520
July1st to 15thDay
5%315%436%6%6%11%47%
2520
16th to endDay
4315%5%47%5%7%8%44%
2566
August1st to 15thDay
6%5%25%6%35%6%6%9%41%
2334
16th to endDay
34146%36%6%7%9%46%
2292
September1st to 15thDay
5%324425%45%7%54%
2160
16th to endDay
5%41432335%7%58%
1857
October1st to 15thDay
5%7%245%24446%51%
1650
16th to endDay
5%6%25%423446%53%
1760
November1st to 15thDay
27%45%423447%53%
1583
16th to endDay
26%36%424347%55%
1494
December1st to 15thDay
110%6%9%7%46%6%6%8%32%
1440
16th to endDay
29%5%12%10%47%6%6%6%30%
1536
January1st to 15thNight
110%6%8%7%34447%40%
2500
16th to endNight
110%6%9%6%23445%44%
2496
February1st to 15thNight
19%6%9%7%2445%7%40%
2277
16th to endNight
18%6%10%6%3445%7%42%
1902
March1st to 15thNight
17%37%423445%54%
2058
16th to endNight
28%35%5%2445%6%51%
2060
April1st to 15thNight
35%35%5%245%6%9%49%
1798
16th to endNight
5%9%345%34447%47%
1800
May1st to 15thNight
5%6%35%6%35%46%8%44%
1583
16th to endNight
43234345%6%10%50%
1497
June1st to 15thNight
21223348%68%
1440
16th to endNight
11221245%8%69%
1440
July1st to 15thNight
2134345%6%12%54%
1440
16th to endNight
2313426%6%7%8%54%
1600
August1st to 15thNight
22145%3446%10%53%
1625
16th to endNight
33134246%5%8%55%
1910
September1st to 15thNight
431342345%7%58%
1800
16th to endNight
2313222347%67%
1807
October1st to 15thNight
5%5%15%32445%7%54%
1980
16th to endNight
5%6%23323336%58%
2112
November1st to 15thNight
37%3441335%6%56%
2262
16th to endNight
17%35%323347%57%
2465
December1st to 15thNight
29%49%8%45%446%40%
2520
16th to endNight
17%6%12%9%45%5%5%7%35%
2688

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%10%18%19%41
1448
16th to endDay
44%8%17%20%8%1
1728
February1st to 15thDay
48%11%15%15%7%1
1575
16th to endDay
45%9%15%20%8%1
1572
March1st to 15thDay
38%6%15%24%13%1
1899
16th to endDay
41%8%12%25%9%2
2163
April1st to 15thDay
41%7%14%20%12%3
2150
16th to endDay
45%8%13%21%9%1
2160
May1st to 15thDay
43%10%11%20%12%
2364
16th to endDay
38%10%12%21%14%2
2620
June1st to 15thDay
24%7%12%18%26%9%
2520
16th to endDay
17%47%23%29%17%
2520
July1st to 15thDay
30%9%11%16%18%13%
2371
16th to endDay
34%9%13%21%14%7%
2406
August1st to 15thDay
36%10%13%16%15%7%
2319
16th to endDay
30%9%13%22%18%5%
2292
September1st to 15thDay
28%7%10%19%23%11%
2160
16th to endDay
26%6%9%30%24%3
1857
October1st to 15thDay
34%6%10%27%18%2
1650
16th to endDay
30%6%12%32%15%2
1760
November1st to 15thDay
33%5%15%23%20%2
1583
16th to endDay
29%7%19%31%10%1
1494
December1st to 15thDay
48%10%16%20%4
1440
16th to endDay
54%9%10%18%5%1
1536
January1st to 15thNight
44%8%17%21%8%1
2500
16th to endNight
41%6%15%23%10%1
2496
February1st to 15thNight
43%11%16%19%7%
2288
16th to endNight
42%7%12%23%10%1
1902
March1st to 15thNight
33%6%15%30%12%1
2058
16th to endNight
34%7%14%32%9%1
2060
April1st to 15thNight
32%9%16%23%16%2
1798
16th to endNight
38%7%12%23%17%
1800
May1st to 15thNight
38%9%12%26%12%
1584
16th to endNight
28%9%16%28%14%2
1498
June1st to 15thNight
15%6%14%26%26%11%
1440
16th to endNight
14%48%23%28%20%
1440
July1st to 15thNight
20%10%20%16%16%15%
1360
16th to endNight
23%7%23%18%16%10%
1497
August1st to 15thNight
24%8%19%20%16%10%
1616
16th to endNight
25%9%12%19%24%8%
1910
September1st to 15thNight
24%5%13%19%22%14%
1800
16th to endNight
19%5%10%32%26%4
1807
October1st to 15thNight
29%7%11%28%18%3
1980
16th to endNight
27%412%33%19%2
2112
November1st to 15thNight
30%5%12%27%19%3
2262
16th to endNight
28%6%16%31%15%1
2465
December1st to 15thNight
44%9%17%20%7%
2520
16th to endNight
50%9%13%19%5%1
2688

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
8%13%26%27%17%5%
90
16th to endDay
5%8%36%28%21%
96
February1st to 15thDay
8%17%35%30%7%
90
16th to endDay
7%18%33%23%16%1
81
March1st to 15thDay
12%23%32%24%7%
189
16th to endDay
11%34%36%13%3
288
April1st to 15thDay
11%31%30%15%7%2
269
16th to endDay
15%32%32%14%31
270
May1st to 15thDay
14%17%28%27%10%1
375
16th to endDay
10%14%29%25%16%3
517
June1st to 15thDay
6%11%27%30%20%3
495
16th to endDay
28%26%32%26%2
495
July1st to 15thDay
9%417%32%32%3
475
16th to endDay
7%321%35%27%5%
425
August1st to 15thDay
11%7%30%32%15%3
315
16th to endDay
5%5%25%40%17%6%
332
September1st to 15thDay
8%15%29%25%14%6%
315
16th to endDay
6%9%30%24%20%7%
172
October1st to 15thDay
7%6%25%26%26%6%
90
16th to endDay
14%7%31%25%20%1
96
November1st to 15thDay
26%28%23%27%11%
90
16th to endDay
11%17%40%26%4
90
December1st to 15thDay
7%20%38%28%4
90
16th to endDay
314%41%37%3
96
January1st to 15thNight
6%16%26%35%14%1
894
16th to endNight
5%11%31%38%11%1
768
February1st to 15thNight
5%8%36%41%8%
704
16th to endNight
5%10%38%38%7%
632
March1st to 15thNight
49%32%39%13%
720
16th to endNight
5%7%35%42%9%
716
April1st to 15thNight
5%11%34%39%8%
539
16th to endNight
9%10%30%35%13%
540
May1st to 15thNight
9%6%25%42%14%1
540
16th to endNight
8%5%22%37%24%1
563
June1st to 15thNight
2422%46%23%1
540
16th to endNight
2117%49%29%
540
July1st to 15thNight
215%39%49%2
510
16th to endNight
3434%53%3
564
August1st to 15thNight
5%7%41%45%
539
16th to endNight
46%39%43%4
573
September1st to 15thNight
5%10%49%30%3
540
16th to endNight
4313%38%36%3
547
October1st to 15thNight
8%5%25%38%19%2
660
16th to endNight
9%6%23%39%19%2
704
November1st to 15thNight
7%9%29%37%15%1
862
16th to endNight
5%10%33%36%12%1
900
December1st to 15thNight
7%13%36%34%7%
900
16th to endNight
415%33%34%10%
960
Page generated at 2017-09-18 06:38:18. Version ac04

Copyright 2017 A. Danko


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