Norman Wells
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Norman Wells clear sky chart from 2005-11-05 to 2017-04-30.

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%
13638
5%
45340
5%
13616
44%
13616
12%
35485

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%
925
5%
3402
4%
925
39%
925
9%
2721
January16th to endNight
39%
992
7%
3344
6%
992
41%
992
11%
2638
February1st to 15thNight
41%
753
9%
2752
9%
750
45%
750
13%
2024
February16th to endNight
50%
650
7%
2201
7%
650
51%
650
12%
1714
March1st to 15thNight
49%
720
13%
2223
11%
720
51%
720
17%
1612
March16th to endNight
51%
723
11%
2034
8%
723
53%
723
20%
1492
April1st to 15thNight
45%
518
2%
1598
2%
518
46%
518
15%
1185
April16th to endNight
51%
358
0%
1253
0%
358
51%
358
17%
861
May1st to 15thNight
48%
330
0%
861
0%
330
48%
330
19%
648
May16th to endNight
57%
228
0%
585
0%
228
57%
228
28%
405
June1st to 15thNight
49%
55
0%
311
0%
55
49%
55
9%
212
June16th to endNight0
0%
16500
0%
86
July1st to 15thNight
52%
114
0%
369
0%
114
52%
114
16%
280
July16th to endNight
58%
242
0%
635
0%
225
59%
225
14%
502
August1st to 15thNight
55%
330
0%
932
0%
328
55%
328
17%
706
August16th to endNight
42%
386
0%
1304
0%
386
42%
386
9%
1070
September1st to 15thNight
52%
525
3%
1515
2%
525
52%
525
19%
1114
September16th to endNight
32%
656
4%
1819
2%
656
34%
656
11%
1486
October1st to 15thNight
39%
660
6%
2086
5%
660
41%
660
11%
1642
October16th to endNight
35%
717
4%
2538
5%
717
36%
717
6%
2146
November1st to 15thNight
38%
904
6%
2857
5%
904
39%
904
9%
2356
November16th to endNight
43%
930
6%
3264
7%
930
43%
930
9%
2646
December1st to 15thNight
34%
930
6%
3497
5%
930
36%
930
7%
2906
December16th to endNight
43%
992
5%
3795
5%
992
43%
992
8%
3033

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
11%9%48%7%46%6%6%8%27%
46498
Night
7%11%6%11%9%46%5%6%8%21%
45407
TransparencyDay
51%11%16%15%3
46071
Night
58%9%13%13%3
45340
SeeingDay
15%5%18%29%23%8%
7222
Night
12%419%31%24%7%
13649

By Month

Percentage Cloud Cover NW (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
5%11%7%11%11%5%6%6%5%8%20%
537
16th to endDay
5%14%48%11%6%6%7%6%11%17%
879
February1st to 15thDay
411%310%8%47%7%6%10%24%
1124
16th to endDay
28%6%12%14%7%8%7%9%8%14%
1271
March1st to 15thDay
29%410%10%6%7%7%8%8%24%
1734
16th to endDay
29%6%12%11%5%7%7%6%7%22%
2188
April1st to 15thDay
10%14%6%9%8%45%6%5%7%22%
2349
16th to endDay
9%10%46%6%45%5%6%8%33%
2688
May1st to 15thDay
13%11%38%5%345%5%7%31%
2760
16th to endDay
13%6%2443445%8%40%
3176
June1st to 15thDay
12%6%25%6%46%6%7%9%32%
3317
16th to endDay
10%426%5%35%6%6%9%38%
3465
July1st to 15thDay
13%6%26%7%47%7%7%9%25%
3229
16th to endDay
12%7%37%7%5%7%6%7%10%24%
3176
August1st to 15thDay
14%8%25%6%35%5%6%9%32%
2692
16th to endDay
21%10%37%6%35%5%6%6%22%
2544
September1st to 15thDay
17%8%36%5%25%5%5%7%32%
2115
16th to endDay
17%15%47%6%3445%6%24%
1811
October1st to 15thDay
13%15%5%8%5%345%5%6%26%
1543
16th to endDay
12%18%6%12%10%46%5%45%13%
1324
November1st to 15thDay
7%12%7%12%10%5%7%6%6%7%16%
996
16th to endDay
6%9%5%15%12%6%7%7%6%11%10%
696
December1st to 15thDay
415%6%11%12%6%8%6%49%14%
462
16th to endDay
412%415%12%5%7%8%9%6%14%
422
January1st to 15thNight
5%12%8%13%10%5%7%5%6%8%17%
3402
16th to endNight
6%13%6%11%10%5%8%6%6%8%17%
3344
February1st to 15thNight
310%6%10%10%5%6%6%7%10%22%
2740
16th to endNight
38%5%11%10%6%9%6%7%7%22%
2201
March1st to 15thNight
29%5%11%7%5%8%5%5%8%29%
2223
16th to endNight
27%5%13%9%5%5%347%34%
2030
April1st to 15thNight
8%13%7%8%5%35%5%6%7%28%
1598
16th to endNight
8%10%36%5%46%46%8%35%
1253
May1st to 15thNight
13%9%46%6%34447%34%
860
16th to endNight
13%6%243145%6%7%42%
585
June1st to 15thNight
16%5%48%5%246%5%9%31%
311
16th to endNight
12%235%8%36%45%11%36%
165
July1st to 15thNight
12%435%6%5%7%9%9%8%29%
398
16th to endNight
10%7%27%6%47%7%8%11%26%
685
August1st to 15thNight
16%6%26%6%45%6%7%9%27%
937
16th to endNight
18%9%49%8%46%6%5%8%20%
1304
September1st to 15thNight
15%8%36%5%35%5%5%8%33%
1515
16th to endNight
16%15%49%6%3445%7%21%
1819
October1st to 15thNight
12%14%5%8%7%35%47%7%22%
2086
16th to endNight
12%16%8%13%8%45%446%15%
2538
November1st to 15thNight
7%15%7%13%10%5%446%7%17%
2857
16th to endNight
5%10%6%13%11%5%8%7%6%8%15%
3264
December1st to 15thNight
6%13%7%14%10%6%8%5%6%8%13%
3497
16th to endNight
412%7%13%10%5%8%6%7%10%14%
3795

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%9%10%14%4
537
16th to endDay
58%8%12%13%6%
879
February1st to 15thDay
49%11%12%17%6%
1124
16th to endDay
61%7%13%11%5%
1271
March1st to 15thDay
52%8%12%21%4
1734
16th to endDay
56%11%11%14%4
2188
April1st to 15thDay
58%13%14%10%2
2349
16th to endDay
47%10%20%18%3
2688
May1st to 15thDay
51%9%16%19%3
2760
16th to endDay
40%8%13%24%11%1
3181
June1st to 15thDay
44%13%14%22%5%
3317
16th to endDay
39%11%18%26%4
3465
July1st to 15thDay
50%14%19%13%2
3030
16th to endDay
51%16%22%9%
2963
August1st to 15thDay
45%15%26%10%1
2672
16th to endDay
58%12%19%9%
2544
September1st to 15thDay
49%12%23%13%1
2115
16th to endDay
59%10%16%10%2
1811
October1st to 15thDay
56%12%16%12%1
1543
16th to endDay
71%10%7%8%2
1324
November1st to 15thDay
65%9%11%11%2
996
16th to endDay
65%11%11%7%3
696
December1st to 15thDay
67%8%12%10%1
462
16th to endDay
62%10%13%10%3
422
January1st to 15thNight
64%8%11%13%2
3402
16th to endNight
61%8%12%11%5%
3344
February1st to 15thNight
53%9%12%14%8%1
2752
16th to endNight
58%9%13%13%4
2201
March1st to 15thNight
51%7%10%24%6%
2223
16th to endNight
50%7%10%23%7%
2034
April1st to 15thNight
54%7%19%15%2
1598
16th to endNight
43%13%21%17%4
1253
May1st to 15thNight
50%9%16%19%3
861
16th to endNight
37%11%13%27%8%1
585
June1st to 15thNight
49%11%12%19%6%
311
16th to endNight
43%9%15%29%3
165
July1st to 15thNight
45%18%20%13%2
369
16th to endNight
46%21%19%12%
635
August1st to 15thNight
49%12%25%8%3
932
16th to endNight
60%13%15%9%
1304
September1st to 15thNight
47%11%23%15%2
1515
16th to endNight
59%11%14%10%2
1819
October1st to 15thNight
57%11%15%12%1
2086
16th to endNight
69%9%11%8%1
2538
November1st to 15thNight
64%9%10%13%1
2857
16th to endNight
62%11%12%10%3
3264
December1st to 15thNight
68%8%10%11%1
3497
16th to endNight
63%9%13%11%2
3795

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
13%13%23%33%10%6%
30
16th to endDay
18%330%26%20%
53
February1st to 15thDay
23%15%15%31%10%5%
60
16th to endDay
6%11%22%29%25%4
168
March1st to 15thDay
5%426%24%26%11%
246
16th to endDay
6%220%28%30%11%
288
April1st to 15thDay
20%7%25%20%21%6%
269
16th to endDay
11%327%26%24%6%
447
May1st to 15thDay
17%5%19%28%22%6%
558
16th to endDay
15%315%34%25%4
609
June1st to 15thDay
16%5%15%33%22%6%
657
16th to endDay
9%318%37%23%6%
750
July1st to 15thDay
15%413%29%24%12%
610
16th to endDay
15%5%15%27%24%10%
619
August1st to 15thDay
15%415%27%26%10%
516
16th to endDay
21%5%17%27%22%6%
400
September1st to 15thDay
21%7%18%27%19%5%
255
16th to endDay
21%11%20%26%16%3
255
October1st to 15thDay
17%10%21%23%17%9%
231
16th to endDay
23%320%23%20%9%
64
November1st to 15thDay
6%5%11%31%21%23%
60
16th to endDay
9%1330%28%26%
53
December1st to 15thDay
11%11%35%17%23%
17
16th to endDay
14%14%71%
7
January1st to 15thNight
10%6%22%30%24%6%
930
16th to endNight
11%5%23%32%20%5%
992
February1st to 15thNight
8%5%22%33%23%6%
758
16th to endNight
6%419%34%26%8%
650
March1st to 15thNight
5%5%19%35%26%7%
720
16th to endNight
4317%32%30%11%
723
April1st to 15thNight
15%217%34%25%5%
518
16th to endNight
10%424%34%21%4
358
May1st to 15thNight
17%319%31%25%2
330
16th to endNight
15%317%34%28%1
229
June1st to 15thNight
16%310%36%29%3
55
July1st to 15thNight
12%216%30%32%5%
114
16th to endNight
13%112%33%36%2
242
August1st to 15thNight
17%311%32%28%6%
330
16th to endNight
22%220%27%20%7%
386
September1st to 15thNight
20%414%31%22%6%
525
16th to endNight
25%7%21%26%16%2
656
October1st to 15thNight
18%7%20%24%23%5%
660
16th to endNight
20%214%28%24%9%
717
November1st to 15thNight
14%416%30%23%9%
904
16th to endNight
9%417%28%27%11%
930
December1st to 15thNight
11%7%23%31%20%6%
930
16th to endNight
9%314%34%29%8%
992
Page generated at 2017-04-30 18:39:59. Version ac04

Copyright 2017 A. Danko


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