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 2017-04-08.

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%
14354
7%
45507
5%
14325
38%
14325
13%
34881

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%
610
7%
1648
5%
610
43%
610
14%
1285
April16th to endNight
35%
415
7%
1405
5%
415
40%
415
13%
1066
May1st to 15thNight
37%
329
4%
1271
4%
329
38%
329
12%
932
May16th to endNight
36%
342
0%
1154
0%
342
36%
342
11%
884
June1st to 15thNight
37%
330
0%
990
0%
330
37%
330
15%
751
June16th to endNight
48%
330
0%
990
0%
330
48%
330
18%
718
July1st to 15thNight
40%
310
0%
1005
0%
310
40%
310
16%
729
July16th to endNight
47%
348
2%
1141
1%
326
50%
326
24%
700
August1st to 15thNight
66%
330
10%
1244
13%
328
68%
328
26%
704
August16th to endNight
47%
522
9%
1572
8%
522
49%
522
18%
1140
September1st to 15thNight
56%
635
14%
1625
8%
635
56%
635
29%
1105
September16th to endNight
39%
656
12%
1817
6%
656
41%
656
17%
1359
October1st to 15thNight
39%
660
9%
1980
7%
660
42%
660
17%
1462
October16th to endNight
28%
704
6%
2329
3%
704
33%
704
10%
1849
November1st to 15thNight
23%
700
7%
2450
5%
700
27%
700
8%
1931
November16th to endNight
28%
809
8%
2704
5%
809
32%
809
11%
2116
December1st to 15thNight
30%
930
7%
2880
5%
930
32%
930
11%
2279
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%46%5%6%6%28%
45783
Night
13%12%5%8%7%35%5%5%6%26%
45652
TransparencyDay
54%9%15%15%4
45428
Night
57%8%14%14%4
45511
SeeingDay
17%12%26%26%14%3
6103
Night
19%9%24%27%16%2
14361

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
11%13%5%9%8%45%6%5%6%23%
2137
16th to endDay
16%13%6%9%7%36%5%45%21%
2225
May1st to 15thDay
12%10%5%8%8%36%5%46%29%
2348
16th to endDay
13%10%47%8%5%7%5%6%6%24%
2605
June1st to 15thDay
14%6%37%7%46%5%5%7%30%
2640
16th to endDay
14%6%47%7%46%6%6%6%28%
2640
July1st to 15thDay
15%7%35%6%46%46%6%33%
2555
16th to endDay
9%5%26%5%36%5%6%7%41%
2636
August1st to 15thDay
5%425%6%35%46%8%46%
2379
16th to endDay
13%5%36%6%45%6%6%7%33%
2277
September1st to 15thDay
11%425%5%35%5%5%7%42%
2005
16th to endDay
15%7%36%6%45%5%6%7%31%
1810
October1st to 15thDay
15%10%38%7%45%5%5%7%26%
1650
16th to endDay
17%12%5%8%6%36%5%6%6%22%
1542
November1st to 15thDay
18%13%37%6%35%5%5%6%24%
1408
16th to endDay
12%15%6%9%5%5%7%5%5%6%19%
1239
December1st to 15thDay
13%12%49%7%37%47%6%23%
1080
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%26%
1648
16th to endNight
13%11%5%8%7%36%5%6%5%26%
1405
May1st to 15thNight
15%10%48%7%445%5%5%28%
1270
16th to endNight
16%8%5%7%7%48%5%5%8%22%
1154
June1st to 15thNight
14%7%46%8%46%6%6%6%27%
990
16th to endNight
13%6%37%5%36%6%8%8%30%
990
July1st to 15thNight
15%5%27%6%35%6%6%7%33%
1072
16th to endNight
11%315%5%35%45%6%44%
1225
August1st to 15thNight
7%4135%245%6%8%50%
1251
16th to endNight
13%6%26%7%35%5%6%7%34%
1572
September1st to 15thNight
11%425%5%24447%45%
1625
16th to endNight
16%8%36%6%35%5%5%7%29%
1817
October1st to 15thNight
16%9%37%5%345%5%7%31%
1980
16th to endNight
19%14%47%6%35%45%5%23%
2329
November1st to 15thNight
18%14%46%6%45%45%7%21%
2450
16th to endNight
11%17%5%9%6%445%46%24%
2704
December1st to 15thNight
15%16%5%7%6%3444426%
2880
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%3
2137
16th to endDay
66%6%10%12%3
2225
May1st to 15thDay
56%6%12%16%7%
2348
16th to endDay
60%9%14%11%3
2609
June1st to 15thDay
52%8%14%16%6%
2640
16th to endDay
54%10%16%16%3
2640
July1st to 15thDay
50%8%15%16%8%
2393
16th to endDay
40%9%22%22%5%
2457
August1st to 15thDay
35%10%24%25%4
2361
16th to endDay
47%11%17%20%3
2277
September1st to 15thDay
40%9%22%22%5%
2005
16th to endDay
51%10%17%17%3
1810
October1st to 15thDay
55%11%16%14%1
1650
16th to endDay
61%12%14%10%1
1542
November1st to 15thDay
59%8%15%11%4
1408
16th to endDay
64%8%11%12%2
1239
December1st to 15thDay
57%11%16%12%2
1080
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
1648
16th to endNight
58%7%14%14%5%
1405
May1st to 15thNight
56%7%11%14%9%
1271
16th to endNight
56%10%13%14%4
1154
June1st to 15thNight
54%9%12%17%6%
990
16th to endNight
48%10%20%17%2
990
July1st to 15thNight
50%9%13%16%9%
1005
16th to endNight
36%8%25%23%5%
1141
August1st to 15thNight
31%9%23%29%5%
1244
16th to endNight
48%10%18%17%4
1572
September1st to 15thNight
38%9%18%26%7%
1625
16th to endNight
52%8%13%20%4
1817
October1st to 15thNight
51%8%18%16%4
1980
16th to endNight
61%8%15%13%1
2329
November1st to 15thNight
62%8%14%11%4
2450
16th to endNight
60%8%13%12%5%
2704
December1st to 15thNight
61%7%14%14%2
2880
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
21%17%30%20%6%3
239
16th to endDay
23%19%26%22%6%1
210
May1st to 15thDay
16%15%28%26%11%2
275
16th to endDay
19%13%23%26%13%3
479
June1st to 15thDay
17%12%25%26%15%2
585
16th to endDay
16%7%24%30%16%4
585
July1st to 15thDay
19%9%23%27%17%2
477
16th to endDay
12%9%25%35%15%1
445
August1st to 15thDay
6%5%21%35%25%5%
324
16th to endDay
16%13%25%32%10%1
268
September1st to 15thDay
15%9%29%21%20%3
255
16th to endDay
21%14%31%16%14%1
255
October1st to 15thDay
24%13%22%22%15%1
255
16th to endDay
25%9%27%21%12%3
148
November1st to 15thDay
28%18%23%20%36%
60
16th to endDay
13%10%28%21%15%11%
60
December1st to 15thDay
11%13%21%15%26%11%
60
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
610
16th to endNight
17%12%28%24%15%1
415
May1st to 15thNight
17%7%24%29%20%
330
16th to endNight
18%7%26%27%16%2
343
June1st to 15thNight
17%8%25%28%19%1
330
16th to endNight
15%424%33%18%3
330
July1st to 15thNight
17%5%25%27%21%2
310
16th to endNight
12%6%26%28%21%3
348
August1st to 15thNight
9%214%35%33%4
330
16th to endNight
15%322%33%21%2
522
September1st to 15thNight
13%320%33%27%2
635
16th to endNight
19%8%26%25%16%3
656
October1st to 15thNight
22%8%20%29%15%2
660
16th to endNight
27%9%24%25%10%1
704
November1st to 15thNight
26%14%27%22%6%2
700
16th to endNight
21%11%29%24%11%1
809
December1st to 15thNight
23%11%23%28%11%1
930
16th to endNight
19%12%25%25%14%2
992
Page generated at 2017-04-09 03:54:14. Version ac04

Copyright 2017 A. Danko


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