Vanderhoof
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vanderhoof clear sky chart from 2005-11-05 to 2017-12-02.

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
35%
15061
7%
47730
5%
15032
38%
15032
13%
36435

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
25%
774
5%
2710
4%
770
28%
770
6%
2290
January16th to endNight
25%
800
8%
2880
6%
800
28%
800
7%
2338
February1st to 15thNight
30%
708
7%
2406
5%
708
33%
708
10%
1897
February16th to endNight
39%
632
10%
2053
8%
632
42%
632
15%
1511
March1st to 15thNight
28%
720
8%
2106
5%
720
32%
720
12%
1662
March16th to endNight
41%
768
9%
2075
5%
767
43%
767
15%
1622
April1st to 15thNight
42%
631
7%
1711
5%
631
43%
631
14%
1335
April16th to endNight
36%
453
8%
1533
6%
453
42%
453
13%
1145
May1st to 15thNight
36%
359
4%
1386
3%
359
37%
359
11%
1034
May16th to endNight
39%
374
0%
1262
0%
374
39%
374
12%
945
June1st to 15thNight
38%
360
0%
1080
0%
360
38%
360
15%
814
June16th to endNight
48%
360
0%
1080
0%
360
48%
360
19%
771
July1st to 15thNight
40%
340
0%
1103
0%
340
40%
340
17%
787
July16th to endNight
50%
376
2%
1239
1%
354
52%
354
25%
750
August1st to 15thNight
67%
360
11%
1358
13%
358
69%
358
29%
744
August16th to endNight
47%
570
9%
1716
8%
570
49%
570
18%
1245
September1st to 15thNight
55%
693
14%
1773
8%
693
56%
693
29%
1205
September16th to endNight
40%
716
12%
1983
7%
716
43%
716
17%
1483
October1st to 15thNight
38%
720
8%
2160
6%
720
42%
720
17%
1599
October16th to endNight
29%
768
7%
2542
4%
768
33%
768
10%
1999
November1st to 15thNight
24%
760
7%
2660
5%
760
27%
760
9%
2088
November16th to endNight
26%
885
7%
2930
4%
885
31%
885
11%
2320
December1st to 15thNight
30%
942
7%
2912
5%
942
32%
942
11%
2300
December16th to endNight
26%
992
7%
3072
3%
992
29%
992
8%
2551

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%10%47%7%45%5%6%6%29%
48752
Night
13%11%48%7%35%5%5%6%27%
47875
TransparencyDay
54%9%15%16%4
48397
Night
56%8%14%14%4
47734
SeeingDay
18%11%26%25%14%3
7089
Night
19%9%24%27%16%2
15068

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
14%14%7%12%9%46%5%5%6%12%
1238
16th to endDay
12%15%6%10%10%4435%6%19%
1344
February1st to 15thDay
14%12%48%8%5%5%46%6%23%
1457
16th to endDay
7%12%7%10%6%345%5%7%29%
1421
March1st to 15thDay
10%15%5%7%8%45%6%6%5%21%
1851
16th to endDay
7%12%5%8%8%37%6%6%7%25%
2144
April1st to 15thDay
12%13%5%9%8%45%6%5%6%22%
2235
16th to endDay
16%14%6%8%7%36%5%45%21%
2427
May1st to 15thDay
13%10%48%7%36%5%46%27%
2563
16th to endDay
12%9%37%8%5%6%5%6%6%26%
2849
June1st to 15thDay
14%6%37%7%46%5%5%7%31%
2880
16th to endDay
13%6%36%7%46%5%6%6%30%
2880
July1st to 15thDay
14%6%25%5%46%46%7%34%
2787
16th to endDay
9%5%26%5%35%5%6%7%41%
2846
August1st to 15thDay
5%4246%35%46%8%48%
2595
16th to endDay
13%5%36%6%45%6%6%8%33%
2485
September1st to 15thDay
11%425%5%35%5%5%7%43%
2187
16th to endDay
16%8%36%6%45%5%6%7%30%
1974
October1st to 15thDay
15%10%37%6%35%5%5%7%27%
1800
16th to endDay
17%12%5%7%6%35%5%6%6%23%
1681
November1st to 15thDay
17%13%38%6%35%45%6%24%
1528
16th to endDay
11%15%7%9%6%5%6%6%5%6%18%
1342
December1st to 15thDay
13%12%49%7%37%47%6%24%
1086
16th to endDay
12%16%6%9%7%36%6%6%6%18%
1152
January1st to 15thNight
13%16%8%10%8%46%5%6%6%14%
2710
16th to endNight
17%12%6%9%8%36%5%5%6%18%
2880
February1st to 15thNight
15%15%5%8%7%35%45%5%23%
2394
16th to endNight
8%10%5%9%7%45%5%5%7%29%
2053
March1st to 15thNight
10%15%5%10%7%36%5%45%24%
2106
16th to endNight
7%11%5%9%7%5%7%6%6%7%25%
2075
April1st to 15thNight
9%13%5%8%6%5%6%6%5%7%25%
1711
16th to endNight
12%10%5%8%6%36%5%6%6%27%
1533
May1st to 15thNight
15%10%48%8%445%5%5%26%
1385
16th to endNight
16%7%47%7%38%5%5%8%24%
1262
June1st to 15thNight
15%6%46%8%46%6%6%6%27%
1080
16th to endNight
12%6%37%5%36%6%8%8%31%
1080
July1st to 15thNight
14%5%27%6%35%5%6%7%34%
1170
16th to endNight
10%315%5%35%5%6%6%45%
1323
August1st to 15thNight
7%4124245%6%8%52%
1365
16th to endNight
13%6%36%7%35%5%6%7%34%
1716
September1st to 15thNight
12%5%25%5%24447%45%
1773
16th to endNight
16%7%36%6%35%5%6%8%29%
1983
October1st to 15thNight
17%9%37%5%345%46%31%
2160
16th to endNight
19%13%47%6%35%45%6%23%
2542
November1st to 15thNight
17%14%5%6%6%45%446%22%
2660
16th to endNight
11%18%5%9%6%445%46%23%
2930
December1st to 15thNight
15%16%5%7%6%3444426%
2912
16th to endNight
11%15%7%9%8%45%5%5%6%19%
3072

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
68%11%11%7%
1238
16th to endDay
63%9%11%10%5%
1344
February1st to 15thDay
60%7%14%11%4
1457
16th to endDay
53%8%15%15%5%
1421
March1st to 15thDay
61%8%11%13%4
1851
16th to endDay
58%8%17%12%2
2144
April1st to 15thDay
61%8%12%14%2
2235
16th to endDay
66%6%10%12%4
2427
May1st to 15thDay
58%6%12%15%6%
2563
16th to endDay
58%8%14%14%3
2853
June1st to 15thDay
52%8%14%17%6%
2880
16th to endDay
52%9%15%17%4
2880
July1st to 15thDay
48%8%16%18%8%
2625
16th to endDay
39%9%22%22%4
2667
August1st to 15thDay
34%10%23%27%5%
2577
16th to endDay
47%11%17%19%3
2485
September1st to 15thDay
39%9%21%23%5%
2187
16th to endDay
52%9%16%17%3
1974
October1st to 15thDay
55%11%15%14%3
1800
16th to endDay
60%12%14%12%1
1681
November1st to 15thDay
59%8%14%11%5%
1528
16th to endDay
64%9%11%12%2
1342
December1st to 15thDay
56%11%15%13%2
1086
16th to endDay
63%11%11%10%3
1152
January1st to 15thNight
68%9%12%7%2
2710
16th to endNight
63%10%11%8%5%
2880
February1st to 15thNight
62%7%11%11%6%
2406
16th to endNight
54%7%15%16%6%
2053
March1st to 15thNight
61%6%12%13%41
2106
16th to endNight
56%8%17%13%4
2079
April1st to 15thNight
57%8%13%15%4
1711
16th to endNight
56%7%14%15%5%
1533
May1st to 15thNight
58%7%11%13%8%
1386
16th to endNight
54%10%13%16%4
1262
June1st to 15thNight
53%9%12%17%5%
1080
16th to endNight
46%10%19%18%5%
1080
July1st to 15thNight
49%9%14%17%9%
1103
16th to endNight
35%8%26%24%4
1239
August1st to 15thNight
29%9%22%30%8%
1358
16th to endNight
48%10%18%18%4
1716
September1st to 15thNight
38%8%17%27%7%
1773
16th to endNight
52%8%13%19%4
1983
October1st to 15thNight
52%8%17%17%4
2160
16th to endNight
60%8%15%13%2
2542
November1st to 15thNight
62%7%13%11%4
2660
16th to endNight
61%8%13%11%4
2930
December1st to 15thNight
61%7%14%14%2
2912
16th to endNight
65%9%11%10%3
3072

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
15%313%18%40%10%
60
16th to endDay
23%17%18%12%18%9%
64
February1st to 15thDay
26%10%27%19%12%3
173
16th to endDay
12%9%32%27%13%4
211
March1st to 15thDay
15%21%39%17%5%
263
16th to endDay
19%14%31%25%7%1
288
April1st to 15thDay
23%15%29%20%7%3
269
16th to endDay
25%17%25%22%7%1
270
May1st to 15thDay
21%15%28%24%9%2
340
16th to endDay
17%13%22%26%15%4
563
June1st to 15thDay
17%11%25%27%15%2
675
16th to endDay
15%7%27%29%15%4
675
July1st to 15thDay
18%9%24%28%16%2
559
16th to endDay
12%8%24%34%17%1
515
August1st to 15thDay
5%5%20%35%25%7%
390
16th to endDay
16%14%26%31%10%1
332
September1st to 15thDay
15%9%29%20%18%5%
315
16th to endDay
23%12%27%19%14%2
315
October1st to 15thDay
25%13%22%20%15%3
315
16th to endDay
29%8%26%20%12%2
191
November1st to 15thDay
27%16%18%21%11%4
90
16th to endDay
15%17%26%17%12%10%
90
December1st to 15thDay
11%12%24%14%25%11%
62
16th to endDay
18%9%17%21%18%14%
64
January1st to 15thNight
22%14%23%25%12%2
774
16th to endNight
23%12%26%25%12%1
800
February1st to 15thNight
22%8%24%26%14%2
713
16th to endNight
12%9%24%29%21%3
632
March1st to 15thNight
18%13%31%24%10%2
720
16th to endNight
13%11%19%32%19%3
768
April1st to 15thNight
16%8%21%31%18%4
631
16th to endNight
17%11%28%25%16%1
453
May1st to 15thNight
18%8%24%29%18%
360
16th to endNight
18%6%25%28%18%2
375
June1st to 15thNight
18%7%25%28%18%1
360
16th to endNight
15%425%33%18%2
360
July1st to 15thNight
17%5%25%28%20%2
340
16th to endNight
11%5%26%30%22%3
376
August1st to 15thNight
8%214%33%34%6%
360
16th to endNight
15%323%33%21%2
570
September1st to 15thNight
13%319%32%27%3
693
16th to endNight
20%7%25%25%18%3
716
October1st to 15thNight
24%7%21%28%15%3
720
16th to endNight
27%10%24%25%11%1
768
November1st to 15thNight
25%14%26%23%7%1
760
16th to endNight
22%12%28%24%10%1
885
December1st to 15thNight
22%11%23%28%12%1
942
16th to endNight
19%12%25%25%14%2
992
Page generated at 2017-12-03 08:16:43. Version ac04

Copyright 2017 A. Danko


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