West Monroe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Monroe clear sky chart from 2005-11-05 to 2017-03-22.

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
53%
14964
25%
45267
19%
14918
59%
14918
32%
26943

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%
900
25%
2327
11%
895
45%
895
31%
1512
January16th to endNight
31%
960
26%
2496
10%
960
40%
960
29%
1660
February1st to 15thNight
35%
803
24%
2211
9%
800
45%
800
31%
1406
February16th to endNight
27%
598
26%
1860
11%
598
39%
598
26%
1157
March1st to 15thNight
37%
540
24%
1980
16%
540
47%
540
23%
1206
March16th to endNight
43%
549
21%
2013
16%
549
51%
549
26%
1185
April1st to 15thNight
42%
494
26%
1647
18%
494
54%
494
33%
917
April16th to endNight
45%
495
25%
1650
22%
495
54%
495
31%
934
May1st to 15thNight
51%
495
21%
1650
19%
495
59%
495
29%
989
May16th to endNight
65%
515
24%
1587
25%
513
68%
513
37%
896
June1st to 15thNight
80%
495
21%
1485
24%
495
82%
495
42%
818
June16th to endNight
77%
495
22%
1485
23%
495
78%
495
38%
850
July1st to 15thNight
76%
465
20%
1395
23%
465
77%
465
37%
801
July16th to endNight
85%
522
20%
1468
24%
489
85%
489
41%
819
August1st to 15thNight
86%
494
23%
1579
28%
491
86%
491
44%
818
August16th to endNight
76%
525
20%
1750
25%
525
76%
525
30%
1045
September1st to 15thNight
73%
495
24%
1650
28%
495
74%
495
31%
984
September16th to endNight
70%
555
30%
1796
29%
555
72%
555
35%
1013
October1st to 15thNight
64%
660
31%
1980
25%
660
68%
660
40%
1090
October16th to endNight
60%
704
35%
2112
27%
704
67%
704
41%
1147
November1st to 15thNight
56%
700
30%
2100
24%
700
62%
700
39%
1167
November16th to endNight
44%
720
32%
2186
22%
720
54%
720
33%
1302
December1st to 15thNight
39%
825
24%
2364
14%
825
47%
825
27%
1520
December16th to endNight
35%
960
21%
2496
11%
960
41%
960
26%
1707

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
12%5%25%5%35%5%5%7%42%
45589
Night
11%42442345%7%49%
45465
TransparencyDay
39%6%10%19%18%5%
45290
Night
33%5%10%19%21%8%
45269
SeeingDay
10%316%24%30%14%
4791
Night
13%422%31%23%3
14964

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%6%2442234445%
1611
16th to endDay
19%7%3431332444%
1728
February1st to 15thDay
17%7%3432433444%
1650
16th to endDay
18%6%35%423325%43%
1622
March1st to 15thDay
17%6%26%5%345%4439%
1980
16th to endDay
11%6%35%5%3445%6%42%
2005
April1st to 15thDay
12%5%246%2445%8%43%
1971
16th to endDay
11%5%36%5%3435%7%42%
1980
May1st to 15thDay
14%6%46%5%45%46%6%36%
1971
16th to endDay
7%326%6%46%6%6%9%40%
2172
June1st to 15thDay
5%3246%36%7%9%10%39%
2145
16th to endDay
5%225%6%5%7%7%8%10%37%
2145
July1st to 15thDay
9%326%6%48%6%7%12%32%
2145
16th to endDay
8%426%6%48%8%8%9%32%
2284
August1st to 15thDay
6%3146%45%7%7%11%42%
2040
16th to endDay
9%435%6%47%6%7%10%34%
2100
September1st to 15thDay
10%425%7%35%6%7%8%38%
1980
16th to endDay
10%42443446%7%47%
1819
October1st to 15thDay
7%425%5%34345%53%
1650
16th to endDay
13%423212235%58%
1760
November1st to 15thDay
10%5%24332345%54%
1758
16th to endDay
14%6%2442433448%
1764
December1st to 15thDay
19%8%26%5%2433439%
1581
16th to endDay
17%7%45%5%23347%38%
1728
January1st to 15thNight
15%5%2432433449%
2327
16th to endNight
19%5%24323335%45%
2496
February1st to 15thNight
14%6%24423345%47%
2202
16th to endNight
16%6%24423336%46%
1860
March1st to 15thNight
15%5%2432435%6%44%
1980
16th to endNight
12%5%25%425%35%449%
2013
April1st to 15thNight
8%413424448%51%
1647
16th to endNight
9%5%2442435%5%51%
1650
May1st to 15thNight
9%426%5%2445%9%44%
1649
16th to endNight
6%32442446%10%50%
1587
June1st to 15thNight
43133345%6%10%54%
1485
16th to endNight
5%3134246%6%9%51%
1485
July1st to 15thNight
7%314435%47%10%46%
1485
16th to endNight
6%2123245%9%13%48%
1576
August1st to 15thNight
32123345%8%13%52%
1589
16th to endNight
7%4244346%8%11%43%
1750
September1st to 15thNight
9%414435%5%5%8%48%
1650
16th to endNight
9%414433345%55%
1796
October1st to 15thNight
6%3145%33247%57%
1980
16th to endNight
11%31331234460%
2112
November1st to 15thNight
10%313313446%56%
2100
16th to endNight
14%5%3442223453%
2186
December1st to 15thNight
17%7%25%323237%45%
2364
16th to endNight
17%7%35%5%2334443%
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
42%3419%22%7%
1612
16th to endDay
44%3316%23%8%
1728
February1st to 15thDay
43%35%18%19%8%
1652
16th to endDay
45%26%16%22%6%
1622
March1st to 15thDay
47%5%8%15%18%5%
1980
16th to endDay
42%5%10%17%21%2
2007
April1st to 15thDay
39%5%9%19%17%7%
1971
16th to endDay
41%48%19%20%4
1980
May1st to 15thDay
47%5%11%15%15%4
1971
16th to endDay
37%8%14%25%12%1
2176
June1st to 15thDay
34%10%14%24%14%
2145
16th to endDay
36%10%14%20%15%3
2145
July1st to 15thDay
39%10%17%21%9%1
2006
16th to endDay
40%12%16%19%9%
2129
August1st to 15thDay
31%10%17%24%14%1
2026
16th to endDay
41%9%14%18%12%2
2100
September1st to 15thDay
40%10%11%18%13%6%
1980
16th to endDay
34%6%9%19%22%8%
1819
October1st to 15thDay
31%5%7%17%22%15%
1650
16th to endDay
30%2416%32%14%
1760
November1st to 15thDay
31%5%6%19%28%8%
1758
16th to endDay
39%45%14%26%10%
1764
December1st to 15thDay
48%46%16%16%6%
1581
16th to endDay
47%48%18%18%4
1728
January1st to 15thNight
38%46%14%26%8%
2327
16th to endNight
42%35%17%21%9%
2496
February1st to 15thNight
39%27%19%21%8%
2211
16th to endNight
40%36%18%20%10%
1860
March1st to 15thNight
40%5%9%16%20%7%
1980
16th to endNight
37%5%8%19%22%5%
2013
April1st to 15thNight
31%5%11%22%19%10%
1647
16th to endNight
33%48%21%25%7%
1650
May1st to 15thNight
36%6%12%21%17%6%
1650
16th to endNight
29%5%15%27%19%2
1589
June1st to 15thNight
24%7%16%31%18%1
1485
16th to endNight
26%9%15%24%19%4
1485
July1st to 15thNight
28%7%24%24%12%2
1395
16th to endNight
22%10%25%26%12%1
1468
August1st to 15thNight
20%8%23%25%18%3
1579
16th to endNight
31%9%19%19%15%3
1750
September1st to 15thNight
32%8%14%21%14%8%
1650
16th to endNight
30%5%8%16%26%12%
1796
October1st to 15thNight
28%48%16%24%18%
1980
16th to endNight
27%35%14%29%19%
2112
November1st to 15thNight
28%49%18%27%11%
2100
16th to endNight
35%35%13%28%13%
2186
December1st to 15thNight
41%48%20%19%6%
2364
16th to endNight
45%37%17%20%5%
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
18%10%40%20%10%1
90
16th to endDay
21%19%38%15%4
96
February1st to 15thDay
17%13%40%25%3
90
16th to endDay
16%11%44%23%31
81
March1st to 15thDay
20%13%46%20%
90
16th to endDay
7%16%28%35%8%2
67
April1st to 15thDay
17%10%30%29%12%
210
16th to endDay
17%7%20%31%20%2
210
May1st to 15thDay
18%228%32%14%3
228
16th to endDay
6%222%26%30%10%
387
June1st to 15thDay
8%6%32%40%10%
420
16th to endDay
5%17%25%39%20%
420
July1st to 15thDay
6%18%25%41%17%
400
16th to endDay
7%1219%42%27%
445
August1st to 15thDay
7%116%44%30%
313
16th to endDay
10%1217%36%32%
268
September1st to 15thDay
9%16%16%39%25%
255
16th to endDay
6%210%21%40%18%
169
October1st to 15thDay
26%30%32%11%
90
16th to endDay
17%22%17%31%10%
96
November1st to 15thDay
20%332%30%13%1
90
16th to endDay
20%436%23%11%4
90
December1st to 15thDay
24%441%15%12%2
90
16th to endDay
17%12%40%19%5%4
96
January1st to 15thNight
18%8%31%32%8%
900
16th to endNight
22%6%35%31%4
960
February1st to 15thNight
17%9%33%32%6%
803
16th to endNight
19%10%37%30%2
598
March1st to 15thNight
17%9%32%35%6%
540
16th to endNight
14%6%31%31%14%
549
April1st to 15thNight
9%9%36%31%11%
494
16th to endNight
13%6%29%37%12%1
495
May1st to 15thNight
11%227%42%15%1
495
16th to endNight
8%116%36%33%3
515
June1st to 15thNight
5%7%39%43%4
495
16th to endNight
418%25%48%12%
495
July1st to 15thNight
6%6%27%48%10%
465
16th to endNight
7%121%53%15%
522
August1st to 15thNight
4318%53%20%
494
16th to endNight
10%325%47%13%
525
September1st to 15thNight
11%5%31%41%9%
495
16th to endNight
10%17%32%42%5%
555
October1st to 15thNight
8%18%30%35%5%
660
16th to endNight
12%318%34%25%4
704
November1st to 15thNight
11%423%35%23%2
700
16th to endNight
15%5%29%30%17%1
720
December1st to 15thNight
21%7%27%33%10%
825
16th to endNight
22%9%28%29%9%
960
Page generated at 2017-03-23 06:36:10. Version ac04

Copyright 2017 A. Danko


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